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Terrestrial Mammal Conservation

 | 
Nick A. Littlewood
, 
Ricardo Rocha
, 
Rebecca K. Smith
, 
et al.

5. Threat: Transportation and service corridors

Testo integrale

1Rytwinski, T. & Fahrig, L. (2015) The impacts of roads and traffic on terrestrial animal populations. Pages 237–246, in: R. van der Ree, D. J. Smith & C. Grilo (eds) Handbook of Road Ecology. John Wiley & Sons, Ltd, UK, https://doi.orgdoi.org/​10.1002/​9781118568170.ch28

Roads & Railroads

5.1. Install tunnels/culverts/underpass under roads

2https://www.conservationevidence.com/​actions/​2514

3Twenty-five studies evaluated the effects on mammals of installing tunnels, culverts or underpass under roads. Eight studies were in the USA7,11–14,18,19,24,25, four were in Australia1,5,15,22, four were in Canada8,9,16,23, two were in Spain3,4, one each was in Germany2, the Netherlands6 and South Korea17 and three were reviews with wide geographic coverage10,20,21.

4COMMUNITY RESPONSE (0 STUDIES)

5POPULATION RESPONSE (3 STUDIES)

6Survival (3 studies): A study in South Korea17 found that road sections with higher underpass density did not have fewer wildlife-vehicle collisions. A review10 found that most studies recorded no evidence of predation of mammals using crossings under roads. A controlled, before-and-after, site comparison study in Australia1 found that overwinter survival of mountain pygmy-possums increased after an artificial rocky corridor, which included two underpasses, was installed.

7BEHAVIOUR (23 STUDIES)

8Use (23 studies): Seventeen of 20 studies (including seven replicated studies and two reviews), in the USA7,11,13,14,18,19,24,25, Canada8,9,16,23, Australia5,15,22, Spain3,4, the Netherlands6, and across multiple continents20,21, found that crossing structures beneath roads were used by mammals3–9,11,14–16,19–22,24,25 whilst two studies found mixed results depending on species18,23 and one study found that culverts were rarely used as crossings by mammals13. One of the studies24 found that crossing structures were used by two of four species more than expected compared to their movements through adjacent habitats. A controlled, before-and-after, site comparison study in Australia1 found that an artificial rocky corridor, which included two underpasses, was used by mountain pygmy-possums. A replicated study in Germany2 found that use of tunnels by fallow deer was affected by tunnel colour and design. A study in the USA12 found that a range of mammals used culverts, including those with shelves fastened to the sides.

9Behaviour change (1 study): A controlled, before-and-after, site comparison study in Australia1 found that after an artificial rocky corridor, which included two underpasses, was installed, dispersal of mountain pygmy-possums increased.

Background
Tunnels, culverts and underpasses may provide safe road crossing opportunities for mammals. A range of different tunnels can be used, including purpose-built wildlife tunnels, culverts that assist with drainage and which can also be used by wildlife, and large passages beneath elevated road section which may sometimes also be used for local vehicle access.
Underpasses are frequently installed in conjunction with wildlife barrier fencing which funnels animals towards the tunnel and prevents them from accessing the road. For this combined intervention, see
Install barrier fencing and underpasses along roads. See also Install tunnels/culverts/underpass under railways.
Studies included here are those where barrier fencing is not installed or not explicitly referred to in the study methods or where at least some underpasses were in unfenced areas. Most studies here report solely on the use of these structures, such as the number of crossings made. There is an absence of studies reporting on wider population-level effects of the presence of these structures.

  • 1 Mansergh I.M. & Scotts D.J. (1989) Habitat continuity and social organisation of the mountain pygmy (...)

10A controlled, before-and-after, site comparison study in 1982–1986 of rock screes and boulder fields on a mountain in Victoria, Australia1 found that an artificial rocky corridor, which included two underpasses, was used by mountain pygmy-possums Burramys parvus and female overwinter survival and male dispersal increased. Over 28 days, mountain pygmy-possum were recorded in a monitored underpass 60 times, bush rats Rattus fuscipes 21 times and dusky antechinus Antechinus swainsonii three times. The overwinter survival of female pygmy-possums was 96 % of that at an undisturbed site after corridor construction, compared to 21 % before. Before construction, sex ratios at the two sites differed, with males not dispersing at the developed site. After construction, both adult and juvenile males dispersed (population before: 25 % male; after: 10 % male). In 1985, a 60-m-long corridor, connecting a fragmented breeding area, was created. This included two adjacent tunnels (1 m diameter) under a road. The corridor and tunnels were filled with rocks to imitate scree. A remotely activated camera monitored one tunnel over 18 days in February–April and 10 days in October–November 1986. Possums were live-trapped in 1982–1986. Population composition was compared at the developed (ski resort) site and one undisturbed site.

  • 2 Woelfel H. & Krueger H.H. (1995) Zur Gestaltung von Wilddurchlässen an Autobahnen [On the design of (...)

11A replicated study in 1994 of tunnels in enclosures in Germany2 found that use of tunnels by fallow deer Dama dama was affected by tunnel colour and design. Deer used one tunnel significantly more in four of six paired trials. A white-painted tunnel was used more than a grey-painted tunnel (732 vs 425 passages) and also more than a black-painted tunnel (294 vs 153 passages). A black base was used more than one without a base (747 vs 584 passage). An unlit tunnel was used more than an indirectly-lit tunnel (581 vs 242). There was no significant difference in the use of tunnels with and without tree stumps within them. Two tunnels were erected in a 0.7-ha enclosure, each 2 m high, 2 m wide and 8 m long. Twenty deer accessed food through the tunnels. Tunnel use was registered by a photo-electric sensor. Trials were run with six tunnel design combinations: both tunnels unpainted; white vs grey; white vs black; black base (and 80 cm up sides) vs no base; indirect light on ceiling vs unlit; tree stumps in tunnel vs no stumps. Tunnels were painted off-white for base, lighting and tree stump trials.

  • 3 Yanes M., Velasco J. & Suarez F. (1995) Permeability of roads and railways to vertebrates: the impo (...)

12A replicated study in 1994 of roads and railways in Madrid province, Spain3 found that all 17 culverts under roads were used by mammals. The highest frequencies of tracks were from wood mice Apodemus sylvaticus (2.5 tracks/day), shrews Sorex spp. (0.5/day) and European rabbits Oryctolagus cuniculus (0.3/day). Rats Rattus sp. (0.1 tracks/day), hedgehogs Erinaceus europaeus (0.01/day), cats (mostly wild cat Felis silvestris — 0.04/day), red fox Vulpes vulpes (0.03/day), genet Genetta genetta (0.02/day) and weasel Mustela nivalis (0.01/day) were also detected. Small mammal use of culverts decreased with increased road width and culvert length and increased with increased culvert height, width and openness. Use by rabbits and carnivores decreased with increasing highway or railway width. Rabbit use also declined with increased boundary fence height (fences ran across culvert entrances, rather than funnelling animals towards them). Vegetation complexity had little influence. Five culverts were monitored under railways, two under a motorway and 10 under local roads. Structural, vegetation and traffic variables were recorded at each culvert. Use was monitored using marble (rock) dust over culvert floors to record tracks. Sampling was undertaken in 1994, over four days each in spring, summer, autumn and winter. Sampling extended to eight days at four culverts when deer were nearby.

  • 4 Rosell C., Parpal J., Campeny R., Jove S., Pasquina A. & Velasco J.M. (1997) Mitigation of barrier (...)

13A replicated study in 1993–1994 along four roads in Catalonia, Spain4 found that underpasses were used by several mammal species. Small mammals used all rectangular culverts and 94 % of circular culverts. Hares Lepus spp. and rabbits Oryctolagus cuniculus used 83 % and 23 % of rectangular and circular culverts respectively whilst carnivores used 88 % and 75 % respectively. Carnivores recorded were weasel Mustela nivalis, beech marten Martes foina, badger Meles meles, genet Genetta genetta and fox Vulpes vulpes. Wild boar Sus scrofa and roe deer Capreolus capreolus also used underpasses. Use was greater by small mammals for underpasses at the same level as the surroundings and those with natural substrate on the floor. Those with water were used less frequently. Rabbits did not use narrow structures (<1.5 m), whereas wild boar used underpasses >7 m wide. A total of 39 circular (1–3 m diameter) and 17 rectangular drains (4–12 m wide) and other underpasses were surveyed along four 10-km sections of road. Underpasses were monitored for four days/ season over a year, in 1993–1994. Animal tracks were monitored using marble power (50 cm wide) across the centre of each structure. Infra-red and photographic cameras were used at entrances.

  • 5 Norman T., Finegan A. & Lean B. (1998) The role of fauna underpasses in New South Wales. Proceeding (...)

14A study in 1996–1997 along a highway in New South Wales, Australia5 found that mammals used three underpasses. Between three and nine native mammal species used each of the tunnels. Common wombat Vombatus ursinus, swamp wallaby Wallabia bicolor, rats (Rattus fuscipes, Rattus lutreolus) and bandicoots (Perameles nasuta, Isoodon macrourus) were the most frequently recorded. Four non-native species also used underpasses. The greatest number of species was recorded in the largest underpass, but the smallest underpass had the greatest frequency of use. A total of 43 native and 57 introduced mammals were killed on the road during the survey. Three underpasses (diameters: 1.5–10 m) were monitored from August 1996 to June 1997. Infra-red camera traps, track counts (sand 2 m inside entrances), trapping and nocturnal searches were used. Road-kill data were also collected.

  • 6 Veenbaas G. & Brandjes J. (1999) Use of fauna passages along waterways under highways. Proceedings  (...)

15A replicated study in 1997–1998 of 53 wildlife passages along waterways under roads at over 20 sites in the Netherlands6 found that all passages were used by mammals. At least 16 mammal species used passages. Waterside banks extending under bridges were used by 14 species and other types of passageways by 10 species. Brown rats Rattus norvegicus, mice and voles were the most frequently recorded mammals (see original publication for details). For all mammals, frequency of use increased with increasing passage diameter and width, but was not affected by substrate. Culverts and bridges were adapted for wildlife, in the 1990s. In 1997, thirty-one passages (0.4–3.5 m wide) were monitored. These included extended banks (unpaved or paved), planks along bridge or culvert walls, planks floating on the water, concrete passageways and plastic gutters covered with sand. In 1998, twenty-two passages were monitored for the effect of width and substrate. These were wooden passageways along bridge or culvert walls (0.2–0.6 m wide). Monitoring involved weekly checks of tracks on sandbeds (for 4–7 weeks) and ink pads (12 weeks in 1997, four weeks in 1998) across passageways.

  • 7 Austin J.M. & Garland L. (2001) Evaluation of a wildlife underpass on Vermont State Highway 289 in (...)

16A study in 2000 along a highway in Vermont, USA7 found that a concrete underpass was used by four mammal species to cross the road. Infra-red monitors recorded 190 confirmed or unconfirmed instances of animals using the tunnel. Where a species was identified, 58 % of occurrences were racoon Procyon lotor, 27 % were mink Neovison vison, 11 % were weasel Mustela frenata and 4 % were skunk Mephitis mephitis. The total number of passages by these species was not stated. The underpass was a concrete block structure, split along the middle by a concrete support. It was 97 m long, 3 m wide and 4 m high. A stream flowed through one tunnel and, at times of high water, through both tunnels, though a sloping floor ensured at least some dry passage. The underpass was monitored discontinuously from June–November 2000, using infrared monitors, cameras and footprint pads.

  • 8 Clevenger A.P., Chruszcz B. & Gunson K. (2001) Drainage culverts as habitat linkages and factors af (...)

17A replicated study in 1999–2000 along two highways in Alberta, Canada8 found that drainage culverts were used by at least nine mammal species. A total of 618 crossings were recorded. Species recorded were coyote Canis latrans (1 % of crossings), American marten Martes americana (12 %), weasel Mustela ermine and Mustela frenata (28 %), snowshoe hare Lepus americanus (3 %), red squirrel Tamiasciurus hudsonicus (4 %), bushy-tailed wood rat Neotoma cinerea (15 %), shrew spp. Sorex spp. (8 %), deer mouse Peromyscus maniculatus (28 %) and vole spp. Arvicolinae (0.5 %). Culvert use was positively correlated with traffic volume (for hare, squirrel and marten), culvert openness (marten), culvert height (weasel), through-culvert visibility (hare) and adjacent shrub cover (hare). A range of factors negatively affected culvert use by mammals (see paper for details). Thirty-six drainage culverts were monitored along a 55-km section of the Trans-Canada highway (two-and four-lane sections, with and without central reservation) and a 24-km section of highway 1A (two lanes, no central reservation). Crossings were determined from sooted track-plates (75 × 30 cm) in each culvert, checked weekly in January–April of 1999–2000 (≥ 12 times/culvert) and tracks in adjacent snow indicating culvert use.

  • 9 Fitzgibbon K. (2001) An evaluation of corrugated steel culverts as transit corridors for amphibians (...)

18A replicated study in 2000 along highways through two wetlands in British Columbia, Canada9 found that culverts were used by small-to medium-sized mammals. Mammals used most of the eight dry culverts. In particular, there were frequent records of racoons Procyon lotor (on 11 % of track plates) and species from the weasel family (on 32 % of track plates — species not stated). Mice, voles and shrews combined were recorded on 31 % of track plates. Racoons also used wet culverts on all nine occasions when tracks were not obscured by water. In 1995, twelve dry corrugated steel pipe culverts (average 35 long, 1 m diameter) were installed at 50-m intervals under a four-lane highway at one wetland. Eight were monitored. At another wetland, two wet cross-drainage corrugated steel pipe culverts (31 m long, 0.6 m diameter) were monitored. Aluminium track-plates, covered with soot, were installed 1–2 m inside each culvert and monitored over nine weekly intervals, in July–October 2000.

  • 10 Little S.J., Harcourt R.G. & Clevenger A.P. (2002) Do wildlife passages act as prey-traps? Biologic (...)

19A review in 2000 of studies investigating whether mammalian predators use wildlife passages under roads and railways as ‘prey-traps’10 found that most studies recorded no evidence of predation in or around passages. Evidence suggested that predator species used different passages to their prey. Only one study, in Australia, suggested that tunnels increased predation risk and that study recorded only one predator in tunnels. However, no studies specifically investigated predator activity, densities or predation rates, or predator-induced prey mortality at passage sites relative to control sites away from passages, or before-and-after passage construction. A literature survey was carried out in July 2000 using BIOSIS (Biological Abstracts) and Proceedings of the First, Second and Third International Conference on Wildlife Ecology and Transportation.

  • 11 Tigas L.A., Van Vuren D.H. & Sauvajot R.M. (2002) Behavioral responses of bobcats and coyotes to ha (...)

20A study in 1998–1999 in a fragmented urban area in California, USA11 found that bobcats Felis rufus and coyotes Canis latrans used underpasses to cross a road. Nine road crossings (two by bobcats and seven by coyotes) out of 24 crossings where culverts were available within 100 m were through culverts and 15 (five by bobcats and 10 by coyotes) were over the road. Traffic levels were higher during crossings through culverts (2.1 cars/minute) than during crossings over the road (0.8 cars/minute). Results were not tested for statistical significance. The study was conducted northwest of Los Angeles from July 1998 to October 1999. Movements of 13 bobcats and nine coyotes were determined from 53 radio-tracking sessions (32 focussed on bobcats, 21 on coyotes). Locations were obtained every 30 minutes for 2–12 hours and road crossings were observed directly when possible.

  • 12 Foresman K.R. (2003) Small mammal use of modified culverts on the Lolo South project of western Mon (...)

21A study in 2001–2003 along a highway through wetlands in Montana, USA12 found that a range of mammals used culverts, including those with shelves fastened to sides. Twenty-three mammal species used culverts. These included six of the seven small mammal species that were recorded by trapping outside tunnel entrances; meadow vole Microtus pennsylvanicus, deer mouse Peromyscus maniculatus, vagrant shrew Sorex vagrans, Columbian ground squirrel Spermophilus columbianus, short-tailed weasel Mustela erminea and striped skunk Mephitis mephitis. Other mammals recorded using culverts included white-tailed deer Odocoileus virginianus, muskrat Ondatra zibethicus, raccoon Procyon lotor, coyote Canis latrans and red fox Vulpes vulpes. When water covered culvert floors, deer mice, short-tailed weasels, striped skunks and raccoons travelled along shelves in culverts. Meadow voles used tubes along culvert shelves. At least ten culverts (total number not clear) were monitored along a 6-mile section of Highway 93. Five had 25-inch-wide shelves installed. Culverts included some of 3–4 feet diameter and may have included others up to 10 feet wide. Monitoring was conducted from October 2001 to 2003 using heat-and motion-triggered cameras. Each month (March–October), small mammal populations adjacent to culverts were censused using 25 live traps, over three days.

  • 13 LaPoint S., Keys R.W. & Ray J.C. (2003) Animals crossing the Northway: are existing culverts useful (...)

22A study in 2002 of mixed habitats including forest, swamp and farmland, along a highway in New York, USA13 found that 19 culverts were rarely used as crossing points by mammals. The only crossings documented were five by northern racoons Procyon lotor at a single drainage culvert. Nineteen culverts were studied, along 141 km of highway, from 14 March to 29 April 2002. Culverts were categorised according to primary use: drainage (seven culverts), pedestrian underpass (nine), truck use (two) or bridge (one, where a river flowed beneath the road). Enabling white-tailed deer Odocoileus virginianus passage was also thought to be a motivation in installing at least some culverts. Animal passage was recorded using one camera trap at each culvert (average 40 days/site) and opportunistic snow-tracking when conditions permitted.

  • 14 Ng S.J., Dole J.W., Sauvajot R.M., Riley S.P.D. & Valone T.J. (2004) Use of highway undercrossings (...)

23A replicated study in 1999–2000 along three major highways in California, USA14 found that tunnels, culverts and underpasses were used by mammals. Fourteen of the 15 passages were used by racoons Procyon lotor (making 207 crossings), eight by opossums Didelphis virginianus (24 crossings), seven by coyotes Canis latrans (59 crossings), seven by bobcats Lynx rufus (36 crossings), five by striped skunks Mephitis mephitis (23 crossings), three by mule deer Odocoileus hemionus (26 crossings), one by spotted skunks Spilogale putorius (five crossings) and one by a mountain lion Puma concolor (one crossing). Crossing numbers include both verified and probable crossings. Rodents and cottontail rabbits Sylvilagus audubonii were also recorded. Six square livestock tunnels, five drainage culverts and four underpasses (surface roads or wide stream crossings) were studied. Passages were 44–218 m long and 2–238 m2 in cross-section. Camera traps were used in four passages and powder stations to detect animal footprints in 12 passages. One passage was monitored using both methods. Monitoring occurred over four consecutive days/month between July 1999 and June 2000.

  • 15 Goosem M., Weston N. & Bushnell S. (2005) Effectiveness of rope bridge arboreal overpasses and faun (...)

24A study in 2001–2003 on a road through rainforest in Queensland, Australia15 found that underpasses beneath the road were used by a range of mammals. There were 237 crossings recorded by brown bandicoots Isoodon obesulus, 233 by red-legged pademelons Thylogale stigmatica, 230 by coppery brushtail possums Trichosurus vulpecula johstoni, two by Lumholtz’s tree-kangaroos Dendrolagus lumholtzi, 53 by rodents and 13 by dogs Canis lupus familiaris or dingoes Canis dingo. Three underpasses (3.4 m high, 3.7 m wide), installed in 2001 below an upgraded two-lane road, were studied. Habitat enhancement features were added to each, such a soil, leaf and branch litter, rocks and logs and also vertical tree branches, to enable escape off the tunnel floor. Underpass use was monitored by weekly checks, over three years, for animal tracks in 1-m-wide strips of sand. Infrared-triggered cameras were used occasionally to confirm identifications.

  • 16 Krawchuk A., Larsen K.W., Weir R.D. & Davis H. (2005) Passage through a small drainage culvert by m (...)

25A study in 2003 of a highway and railway in British Columbia, Canada16 found that at least two of three crossing structures were used by mammals. Mule deer Odocoileus hemionus were detected using one small culvert (2.1 m wide, 1.5 m high, 30 m long) six times. They were not recorded using a larger (7 m wide, 5 m high, 40 m long) cattle underpass though signs of their presence were noted nearby. Black bears were detected 20 times passing through the smaller culvert and four times through the cattle underpass. Raccoons were detected twice at the cattle underpass. The smaller culvert had a soil substrate, was surrounded by vegetation and was relatively far from human activity. The cattle underpass had limited surrounding natural vegetation. No mammals were recorded using a third culvert (1.2 m wide and high, 30 m long), possibly due to camera malfunction. Culverts and the underpass ran under both the Trans-Canada Highway and Canadian Pacific Railway. They were monitored using infrared sensor cameras during August–November 2003. Animal tracks or signs around camera stations were also recorded.

  • 17 Choi T.-Y. & Park C.H. (2007) Can wildlife vehicle collision be decreased by increasing the number (...)
  • 18 Choi T.-Y. & Park C.H. (2007) Can wildlife vehicle collision be decreased by increasing the number (...)
  • 19 LaPoint S., Keys R.W. & Ray J.C. (2003) Animals crossing the Northway: are existing culverts useful (...)
  • 20 Foresman K.R. (2003) Small mammal use of modified culverts on the Lolo South project of western Mon (...)

26A study in 2004–2006 in an area of rice fields and scattered forest in Jeollanamdo province, South Korea17 found that highway underpasses were used by a range of mammals, though road sections with higher underpass density did not have fewer wildlife-vehicle collisions. Eleven wild mammal species were recorded using underpasses. The most frequent were raccoon dog Nyctereutes procyonoides (865 images), brown rat Rattus norvegicus (455), leopard cat Prionailurus benalensis (253), striped field mouse Apodemus agrarius (229), Siberian weasel Mustela sibirica (166), Eurasian otter Lutra lutra (35) and water deer Hydropotes inermis (32). Ninety-three roadkill mammals of 12 species were recorded. The most frequent were rodents (24 casualties), leopard cat18, Siberian weasel19 and water deer20. Most mammals used all underpass types frequently, except water deer, which rarely used small passages. Use of seven circular culverts (0.8–1.2 m diameter), two box culverts (2.5 m wide and high) and five human underpasses (2.0–4.3 m wide and high), selected from 31 underpasses along a 6.6-km section of four-lane highway, were monitored from September 2005–August 2006. One or two infrared-operated cameras were installed 1–2 m inside each underpass for an average of 239 days/underpass. Wildlife-vehicle collisions were recorded daily from September 2004–August 2006.

  • 21 Donaldson B. (2007) Use of highway underpasses by large mammals and other wildlife in Virginia: fac (...)

27A study in 2004–2005 at seven sites along roads through forest in Virginia, USA21 found that white-tailed deer Odocoileus virginianus used underpasses to cross the road but black bears Ursus americanus did not. White-tailed deer crossed through four of seven underpasses monitored, with a total of 1,107 crossings detected. Black bears approached one underpass entrance three times, but did not cross through. Other mammals recorded in underpasses included opossums Didelphis virginiana, bobcats Lynx rufus, red foxes Vulpes vulpes, coyotes Canis latrans, raccoons Procyon lotor and groundhogs Marmota monax as well as squirrels and mice (see paper for details). Seven underpasses were monitored. Five were culverts (1.8–6.1 m wide, 1.8–4.6 m high and 21–79 m long). Two were crossings under bridges (13–94 m wide, 5–14 m high and 10–18 m long). Underpasses were not fenced and most had a narrow water section. Underpasses were monitored from June 2004 to May 2005, using one or two camera traps at each entrance.

  • 22 Kleist A.M., Lancia R.A. & Doerr P.D. (2007) Using video surveillance to estimate wildlife use of a (...)

28A study in 2003–2005 along a highway through deciduous woodland in North Carolina, USA22 found that mammals used a wildlife underpass. An estimated 299 mammal crossings of at least 10 species occurred (based on 126 crossings observed on a sample of video surveillance). Of these, an estimated 185 were white-tailed deer Odocoileus virginianus crossings. At least 17 deer approached the underpass but retreated without crossing. Other mammals crossing included red or grey fox Vulpes vulpes or Urocyon cinereoargenteus, raccoon Procyon lotor, woodchuck Marmota monax, gray squirrel Sciurus carolinensis and chipmunk Tamias striatus. Only four incidences of mammals killed by vehicles were recorded from December 2003 to June 2005. Two digital ultra-low-light video cameras and infrared spotlights monitored underpass use below a four-lane highway between December 2003 and May 2005. A sample of videos was viewed from 458 days of continual video recordings. The underpass was constructed in 1955, encompassing a 6-m width either side of a stream. It was 2–3 m high and 41 m long. Weekly surveys of vehicle-killed animals were undertaken on a 1.8-km section of road encompassing the underpass.

  • 23 van der Ree R., van der Grift E., Mata C. & Suarez F. (2007) Overcoming the barrier effect of roads (...)

29A global review in 2007 of 123 studies investigating the use of 1,864 wildlife crossings23 found that all studies reported that the majority of underpasses and overpasses were used by wildlife. Of the 1,864 structures reported on, most were underpasses (83 %), including culverts (742 examples), bridges (130), tunnels (340) and unknown types (333). Structures provided crossings over or under roads (113 studies), railways (5 studies), both (1 study), canals (2 studies) and a pipeline (1 study). Studies were from Europe (55 studies), the USA (30 studies), Canada (nine studies), South America (one study) and Australia (29 studies).

  • 24 Taylor B.D. & Goldingay R.L. (2010) Roads and wildlife: impacts, mitigation and implications for wi (...)

30A review of 30 studies reporting on monitoring of 329 crossing structures in Australia, Europe and North America24 found that mammals used most culverts and underpasses. Small mammals used pipes (demonstrated by 6/7 relevant studies), drainage culverts (5/5 studies), adapted culverts (5/5 studies), wildlife underpasses (3/4 studies) and bridge underpasses (2/3 studies). Arboreal mammals used pipes (1/1 studies), drainage culverts (4/4 studies), adapted culverts (4/4 studies) and bridge underpasses (1/1 studies). Medium-sized mammals used pipes (8/11 studies), drainage culverts (12/13 studies), adapted culverts (8/8 studies), wildlife underpasses (6/8 studies) and bridge underpasses (6/7 studies). Large mammals used pipes (6/9 studies), drainage culverts (11/12 studies), adapted culverts (11/11 studies), wildlife underpasses (24/24 studies) and bridge underpasses (14/15 studies). Larger mammals tended to use more open underpasses. Small and medium-sized mammals used underpasses with funnel-fencing or adjoining walls and those with vegetation cover close to entrances. Those with vegetation cover tended to be avoided by some ungulates. Thirty papers reporting monitoring of 329 crossing structures were reviewed. Fourteen papers investigated multiple structure types, resulting in a total of 52 studies of different structure types. Underpasses, from small drainage pipes to dry passage bridges, comprised 82 % of crossings.

  • 25 Crook N., Cairns S.C. & Vernes K. (2013) Bare-nosed wombats (Vombatus ursinus) use drainage culvert (...)

31A study in 2010 of a road through forest and pastureland in New South Wales, Australia25 found that bare-nosed wombats Vombatus ursinus used culverts to cross the road. Bare-nosed wombats used eight out of 19 monitored culverts. Wombats were recorded using culverts on 16 out of 190 camera-trap nights. One culvert was used three times in one night and three were used twice in one night. Other culverts were not used more than once in a night. The study was conducted along 8 km of a two-lane road. Nineteen concrete pipe culverts (40–60 cm diameter and 13–25 m long) were monitored between April and August 2010. A camera trap was set 1 m from each culvert entrance for 10 days. Five culverts were dry with earth substrate, nine were dry without earth substrate and five had constant water flow. Culverts were 40–2,200 m apart.

  • 26 D’Amico M., Clevenger A.P., Román J. & Revilla, E. (2015) General versus specific surveys: Estimati (...)

32A study in 2009 at 10 sites along a highway through forest in Alberta, Canada26 found that North American deer mice Peromyscus maniculatus used underpasses to cross a road but meadow voles Microtus pennsylvanicus and southern red-backed voles Myodes gapperi did not. Tracks of deer mice were recorded in 90 % of track tubes in elliptical culverts, in 87 % of track tubes in box culverts and in 75 % of track tubes on open-span bridge underpasses. No tracks of meadow vole or southern red-backed vole were detected, despite their use of overpasses in the area. Over two weeks in September–October 2010, small mammals were surveyed in three elliptical metal culverts (4 m high, 7 m wide), five concrete box culverts (2.6 m high, 3.2 m wide) and two open-span bridge underpasses (3 m high, 11 m wide). Underpasses were unvegetated and entrances were characterized by roadside grasslands. Two parallel sample lines, each of five 30 × 10 cm track tubes with sooted metal sheet as a floor, were placed in the centre of each underpass. Mammals were identified from their footprints.

  • 27 Andis A.Z., Huijser M.P. & Broberg L. (2017) Performance of arch-style road crossing structures fro (...)

33A study in 2015 along a highway in Montana, USA27 found that underpasses were used by white-tailed deer Odocoileus virginianus and mule deer Odocoileus hemionus more than expected compared to their movements through adjacent habitats, but no difference was found for black bear Ursus americanus or coyote Canis latrans. Overall, white-tailed deer (recorded at all 15 underpasses) and mule deer (at five of 15 underpasses) had an average of 88 % and 472 % more movements/ day respectively through underpasses than adjacent habitats. Black bear (recorded at seven of 15 underpasses) and coyote (at 13 of 15 underpasses) had an average of 112 % and 75 % more movements/day respectively through underpasses than adjacent habitats, but the difference was not significant. Fifteen elliptical underpasses were installed in 2006–2011 along a 91 km stretch of highway. Underpasses (7–8 m wide, 4–6 m high, 15–40 m long) were constructed from corrugated metal with a soil substrate and retaining walls extending 10 m from the roadside. Twelve of the 15 underpasses had 2.4-m high wildlife exclusion fencing. Infrared cameras recorded large mammal movements through each underpass (one camera/entrance) and at random locations within an adjacent 300 m2 plot on each side (five cameras/plot) for 12–20 days in April–November 2015.

  • 28 Sparks J.L. & Gates J.E. (2017) Seasonal and regional animal use of drainage structures to cross un (...)

34A replicated study in 2008–2011 of 265 culverts throughout Maryland, USA28 found that culverts were used by a range of mammal species to cross roads. Crossings were made by northern raccoons Procyon lotor (0.79/culvert/day), Virginia opossums Didelphis virginiana (0.03/ culvert/day), woodchucks Marmota monax (0.03/culvert/day), red foxes Vulpes vulpes (0.03/culvert/day), gray squirrels Sciurus carolinensis (0.02/culvert/day) and both common grey foxes Urocyon cinereoargenteus and white-footed mice Peromyscus spp (0.01/culvert/day). Between August 2008 and January 2011, a total of 265 randomly selected culverts were monitored using camera traps for a total of 31,317 camera-trap days. Culverts were located under paved roads and contained either a waterway, a route for water flow, or other depression. Culverts averaged 2.4 m wide, 1.9 m high and 46.4 m long. Each culvert was sampled at least nine times in 2008–2011, for 10–36 days each time, using one camera trap. The camera was placed at the approximate midpoint of the culvert or near the entrance.

5.2. Install tunnels/culverts/underpass under railways

35https://www.conservationevidence.com/​actions/​2519

36Six studies evaluated the effects on mammals of installing tunnels, culverts or underpass under railways. Two studies were in Spain2,3, one was in each of Australia1, Canada5 and the Netherlands6 and one reviewed literature from a range of countries4.

37COMMUNITY RESPONSE (0 STUDIES)

38POPULATION RESPONSE (1 STUDY)

39Survival (1 study): A review4 found that most studies recorded no evidence of predation in or around passages under railways or roads of mammals using those passages.

40BEHAVIOUR (5 STUDIES)

41Use (5 studies): Five studies, in Spain2,3, Australia1, Canada5 and the Netherlands6, found that tunnels, culverts and underpasses beneath railways were used by a range of mammals including rodents1,2,3,6, rabbits and hares2,3,6, carnivores2,3,5,6, marsupials1, deer5 and bears5. One of these studies found that existing culverts were used more than specifically designed wildlife tunnels1.

Background
Tunnels, culverts and underpasses may provide safe railway crossing opportunities for wildlife. A range of different tunnels can be used, often in combination with wildlife barrier fencing which funnels animals towards the tunnel and prevents them from accessing the railway (see Install barrier fencing along railways). Studies summarised within this intervention cover both tunnels created specifically for wildlife and those that were created for other purposes (e.g. drainage or farm access) but where information about use of such structures by mammals is included. Studies mostly report on the use of these structures, such as the number of crossings made, rather than on wider population-level effects of their presence.
See also:
Install tunnels/culverts/underpass under roads and Install overpasses over roads/railways.

  • 29 Hunt A., Dickens H.J. & Whelan R.J. (1987) Movement of mammals through tunnels under railway lines. (...)

42A site comparison study in 1984–1985 in New South Wales, Australia29 found that small and medium-sized mammals used established drainage culverts, but rarely used new wildlife tunnels. All five existing culverts were used by mammals. Bush rat Rattus fuscipes was recorded in all culverts (1–6 captures and/or tracks/culvert) and long-nosed bandicoot Perameles nasuta in one. Few signs of use were recorded in wildlife tunnels. Swamp wallaby Wallabia bicolor tracks were recorded in one tunnel in October 1984. No indication of tunnel use was found in January 1985. Five long-established drainage culverts (0.2 × 0.9 to 2.4 × 3.0 m) with dense surrounding vegetation and three of seven newly constructed wildlife tunnels (3 m diameter, 15–20 m long) with sandy floors and little vegetation, under a 35-km-long section of railway line, were monitored. Small mammal traps were set in all underpasses and cage traps in tunnels and one culvert. Tracks were recorded in sand and on soot-coated paper across passages. Culverts were surveyed for eight nights in September–October 1984 and tunnels for seven nights in October 1984 and five nights in January 1985 (15–242 trap nights/ structure).

  • 30 Yanes M., Velasco J.M. & Suarez F. (1995) Permeability of roads and railways to vertebrates: the im (...)

43A replicated study in 1994 of 17 culverts under roads and railways in Madrid province, Spain30 found that mammals used all 17 culverts studied. The highest frequencies of tracks were from wood mice Apodemus sylvaticus (2.5 tracks/culvert/day), shrews Sorex spp. (0.5/ culvert/day) and European rabbit Oryctolagus cuniculus (0.3/culvert/ day). Rats Rattus sp. (0.1 tracks/culvert/day), hedgehogs Erinaceus europaeus (0.01/culvert/day), cats (mostly wild cat Felis silvestris -0.04/ culvert/day), red fox Vulpes vulpes (0.03/culvert/day), genet Genetta genetta (0.02/culvert/day) and weasel Mustela nivalis (0.01/culvert/ day) were also detected. Small mammal use of culverts decreased with increased culvert length and increased with increasing culvert height, width and openness. Use by rabbits and carnivores decreased with increasing width of the railway or highway. Rabbit use also declined with increased boundary fence height. Vegetation complexity had little influence. Five culverts were monitored under railways, two under a motorway and 10 under local roads. Structural, vegetation and traffic variables were recorded at each culvert. Use was monitored using marble (rock) dust over culvert floors to record tracks. Sampling was undertaken in 1994, over four days each in spring, summer, autumn and winter. Sampling of four culverts extended to eight days when deer were in the vicinity.

  • 31 Rodriguez A., Crema G. & Delibes M. (1996) Use of non-wildlife passages across a high speed railway (...)

44A study in 1991–1992 along a high-speed railway through agricultural land in Castilla La Mancha, Spain31 found that culverts and underpasses not specifically designed for wildlife were used as crossings under the railway by a range of mammals. Small mammals were recorded in culverts/underpasses (and two overpasses) 582 times (37 crossings/100 passage-days) and brown hare Lepus granatensis and European rabbit Oryctolagus cuniculus 89 times (5 crossings/100 passage-days). Tracks of four carnivore species, red fox Vulpes vulpes, wild cat Felis silvestris, common genet Genetta genetta and Iberian lynx Lynx pardinus, were recorded. No deer or wild boar Sus scrofa used passages. Rabbit and hare crossing rates were not affected by underpass design, vegetation cover at entrances or distance from scrubland. Small mammals preferred culverts ≤2 m wide. Fencing did not significantly affect relative crossing rates. Fifteen dry culverts and passages (e.g. small roads and two flyovers, 13–64 m long, 1.2–6.0 m wide, 1.2–3.5 m high) along a 25-km section of high-speed railway, were monitored. Tracks in sand were monitored at each passage for 15–22 days/month between September 1991 and July 1992. The railway was fenced with 2-m-high wire netting in July 1991–March 1992.

  • 32 Little S.J., Harcourt R.G. & Clevenger A.P. (2002) Do wildlife passages act as prey-traps? Biologic (...)

45A review in 2000 of studies investigating whether mammalian predators use wildlife passages under railways and roads as ‘prey-traps’32 found that most studies recorded no evidence of predation in or around passages. Evidence suggested that predator species used different passages to their prey. Only one study, in Australia, suggested that tunnels increased predation risk and that recorded only one predator in tunnels. However, no studies specifically investigated predator activity, densities or predation rates, or predator-induced prey mortality at passage sites relative to control sites away from passages, or before-and-after passage construction. A literature survey was carried out in July 2000 using BIOSIS (Biological Abstracts) and Proceedings of the First, Second and Third International Conference on Wildlife Ecology and Transportation.

  • 33 Krawchuk A., Larsen K.W., Weir R.D. & Davis H. (2005) Passage through a small drainage culvert by m (...)

46A study in 2003 of culverts under a railway and highway in British Columbia, Canada33 found that at least two of three underpasses were used by mammals. Mule deer Odocoileus hemionus were detected using one small culvert (2.1 m wide, 1.5 m high, 30 m long) six times. They were not recorded using a larger (7 m wide, 5 m high, 40 m long) cattle underpass though signs of their presence were noted nearby. Black bears were detected 20 times passing through the smaller culvert and four times through the cattle underpass. Raccoons were detected twice at the cattle underpass. The smaller culvert had a soil substrate, was surrounded by vegetation and was relatively far from human activity. The cattle underpass had limited surrounding natural vegetation. No mammals were recorded using a third culvert (1.2 m wide and high, 30 m long), possibly due to camera malfunction. Culverts and the underpass ran under both the Canadian Pacific Railway and Trans-Canada Highway. They were monitored using infrared sensor cameras during August–November 2003. Animal tracks or signs around camera stations were also recorded.

  • 34 van Vuurde M.R. & van der Grift E.A. (2005) The effects of landscape attributes on the use of small (...)

47A study in 2003 at 14 underpasses beneath a railway through suburban and rural habitat in the Netherlands34 found that several species of small-and medium-sized mammals used underpasses to cross the railway. Tracks identified in the monitored underpasses were from western hedgehog Erinaceus europaeus (recorded at two of the 14 underpasses), rabbit Oryctolagus cuniculus (two underpasses), brown rat Rattus norvegicus (4–5 underpasses), western polecat Mustela putorius (0–1 underpasses), red fox Vulpes vulpes (one underpass), mice, voles and shrews (13 underpasses), weasel Mustela nivalis and stoat Mustela erminea (11 underpasses) and pine Martes martes and stone marten Martes foina (one underpass). Ranges in the number of underpasses used reflect uncertainties in track identification. Fourteen underpasses (0.6 m wide, 0.3 m high and 19–32 m long), were installed beneath a 12-km stretch of railway in 1998–2003. Eleven underpasses were topped with grates (2–9 m long) between entrances and railway tracks. Mammal use was monitored between August and October 2003, using ink track-plates (0.6 × 2.4 m). Track-plates were checked on average at eight-day intervals.

5.3. Modify culverts to make them more accessible to mammals

48https://www.conservationevidence.com/​actions/​2522

49One study evaluated the effects of modifying culverts to make them more accessible to mammals. This study was in the USA1.

50COMMUNITY RESPONSE (0 STUDIES)

51POPULATION RESPONSE (0 STUDIES)

52BEHAVIOUR (1 STUDY)

53Use (1 study): A replicated, site comparison study in the USA1 found that modified culverts (with a dry walkway, open-air central section and enlarged entrances) were used more by bobcats to make crossings than were unmodified culverts.

Background
Culverts under roads may be used as crossing routes by mammals. This use reduces collision-associated risks to mammals and to motorists compared with crossings over the road surface. Some culverts may be less suited as crossing routes than others. For example, culverts with water flowing across their entire width may not be used by some mammals whilst tunnel length may also be a barrier to their use. A range of modifications can be made to try to increase culvert suitability for use by wild mammals.

  • 35 Cain A.T., Tuovila V.R., Hewitt D.G. & Tewes M.E. (2003) Effects of a highway and mitigation projec (...)

54A replicated, site comparison study in 1997–1999 in dry shrubland along a highway in Texas, USA35 found that modified culverts were used more by bobcats Lynx rufus than were unmodified culverts. Use of crossings by cat spp. was higher at modified culverts (2.6 visits/month) than at unmodified culverts (0.5 visits/month). The rate of crossings at bridges (2.2 visits/month) was similar to that at modified culverts. Most cats recorded were bobcats, which accounted for 371 of 471 camera-trap images obtained at culvert entrances. Remaining images were of feral cats Felis catus. Five modified culverts, nine unmodified culverts and four bridges were monitored. Modified culverts had elevated central catwalks (to facilitate a dry crossing even when water was flowing through), open-air sections at the road centre (but fenced, to prevent escape at this part) and enlarged entrances. Crossings were checked two times/week from 1 July 1997 to 31 May 1999 for tracks. Remote cameras were used at seven crossings at a time, from 1 August 1997 to 31 May 1999, and were rotated among all crossings.

5.4. Install ledges in culverts under roads/railways

55https://www.conservationevidence.com/​actions/​2523

56Three studies evaluated the effects on mammals of installing ledges in culverts under roads or railways. Two studies were in the USA1,3 and one was in Portugal2.

57COMMUNITY RESPONSE (0 STUDIES)

58POPULATION RESPONSE (0 STUDIES)

59BEHAVIOUR (3 STUDIES)

60Use (3 studies): A replicated, controlled study in Portugal2 found that under-road culverts with ledges were used more than culverts without ledges by two of five mammal species. A before-and-after study in the USA3 found that installing ledges within under-road culverts did not increase the number or diversity of small mammal species crossing through them, and only one of six species used ledges. A study in the USA1 found that ledges in under-road culverts were used by nine of 12 small mammal species and ledges with access ramps were used more often than those without.

Background
Culverts may be installed under roads to enable drainage. They are sometimes also used by mammals to cross under the road and, in some cases, roadside fencing will be designed to funnel mammals towards culvert entrances. However, some mammals are resistant to passing through tunnels that have water at their base (Serronha
et al. 2013). Ledges may be installed on the sides of culverts, above the usual water level, to assist animal passage.
See also:
Install tunnels/culverts/underpasses under roads and Install tunnels/culverts/underpasses under railways.

61Serronha A.M., Mateus A.R.A., Eaton F., Santos-Reis M. & Grilo C. (2013) Towards effective culvert design: monitoring seasonal use and behavior by Mediterranean mesocarnivores. Environmental Monitoring and Assessment, 185, 6235–6246.

  • 36 Meaney C.A., Bakeman M., Reed-Eckert M. & Wostl E. (2007) Effectiveness of ledges in culverts for s (...)

62A study in 2005–2006 at six road sites in Colorado, USA36 found that ledges in under-road culverts were used by nine of 12 small mammal species and ledges with access ramps were used more often than ledges without access ramps. Nine of 12 small mammal species that passed through the culverts used ledges (see original paper for details). Overall, a greater number of small mammal crossings were recorded along ledges with access ramps installed (total 443 crossings) than along those without (total 262 crossings). Temporary wooden ledges (15 cm wide) were installed in six concrete culverts (1–5 m wide, 1–1.3 m high, 9–48 m long) containing water. At each of the six culverts, access ramps were alternately attached or removed for 8–10 two-week periods in May–September 2005 and 2006. Motion-sensor cameras recorded small mammal movements through the culverts during a total of 16–20 weeks in May–September 2005 and 2006.

  • 37 Villalva P., Reto D., Santos-Reis M., Revilla E., & Grilo C. (2013) Do dry ledges reduce the barrie (...)

63A replicated, controlled study in 2008–2009 of 32 culverts under roads in southern Portugal37 found that under-road culverts with ledges were used more by two mammal species, less by two species and to a similar extent by one species compared to culverts without ledges. Culverts with ledges were used more by stone marten Marte foina and genet Genetta genetta (data reported as model results). However, red fox Vulpes vulpes and badger Meles meles used culverts with ledges less than they used those without ledges (data reported as model results). The use of culverts by European otter Lutra lutra was not altered by the presence of ledges (data reported as model results). In January–March 2008, wooden ledges, 50 cm wide, were installed in 15 culverts and no ledges were installed in 17 culverts. Two video cameras with movement and heat sensors were placed at one entrance of each culvert. Marble dust was spread covering the width of the culvert for monitoring footprints. Each culvert was monitored for seven consecutive nights, in each season, for a year after ledge installation.

  • 38 Kelley, A. (2014) A test of simple ledges for facilitating mammal passage through inundated culvert (...)

64A before-and-after study in 2012–2013 at seven road sites in New York, USA38 found that installing ledges within under-road culverts did not increase the number or diversity of small mammal species crossing through them, and only one of six species used ledges. Overall, a similar number of small mammal crossings of six species were recorded in the seven culverts before (total 55 crossings) and after (total 58 crossings) ledges were installed, although no statistical tests were carried out. Racoons Procyon lotor were the only species recorded using ledges and did so during 58 % of crossings, but similar numbers were recorded before (total 47 crossings) and after (total 41 crossings) ledge installation. In May–June 2013, plywood ledges (14 cm wide) and access ramps were installed through seven under-road culverts (1–3 m wide, 1–2 m high, 6–25 m long) containing water. Cat food was placed on ledges and ramps once after installation. A motion-sensor camera monitored each of the seven culverts for 12 weeks in June–September before (2012) and after (2013) ledges were installed.

5.5. Dig trenches around culverts under roads/railways

65https://www.conservationevidence.com/​actions/​2524

66One study evaluated the effects on mammals of digging trenches around culverts under roads and/or railways. This study was in South Africa1.

67COMMUNITY RESPONSE (0 STUDIES)

68POPULATION RESPONSE (1 STUDY)

69Survival (1 study): A replicated, randomized, controlled, before-and-after study in South Africa1 found that digging trenches alongside culverts did not reduce mammal mortality on roads.

70BEHAVIOUR (0 STUDIES)

Background
Collisions with vehicles can be a large cause of mortality for mammal species (e.g. Forman & Alexander 1998). Underpasses installed beneath roads or drainage culverts may be made accessible to mammals with the intention of increasing connectivity of habitats and reducing the animal-vehicle collision risk associated with crossing the road. A range of means may be employed to help funnel animals towards such crossing points. These are usually fences or similar barriers to prevent animal crossings. However, trenches may be dug at some sites with the intention of inhibiting crossings, especially of small mammals.
See also: Tr
ansportation and Service Corridors: Install barrier fencing along roads.

71Forman R.T.T & Alexander L.E. (1998) Roads and their major ecological effects. Annual Review of Ecology and Systematics, 29, 207–231.

  • 39 Collinson W.J., Davies-Mostert H.T. & Davies-Mostert W. (2017) Effects of culverts and roadside fen (...)

72A replicated, randomized, controlled, before-and-after study in 2015 along a road through dry savanna in Limpopo, South Africa39 found that digging trenches alongside culverts did not reduce the number of mammals killed on roads. Results were not tested for statistical significance. One mammal (a South African pouched mouse Saccostomus campestris) was detected as a roadkill near culverts after trenches were dug and one (a red veld rat Aethomys chrysophilus) was found before they were dug. Over the same period, near culverts where no trenches were dug, two multimammate rats Mastomys spp. were detected as roadkills after trenches were dug at treatment sites and one was found before trenches were dug. The study was conducted in January–February 2015 along 400-m-long road sections with 2-m-wide culverts. In three sections, a 30-cm-deep trench, 2 m from the road verge, was dug for 200 m on either side of the culvert. Three road sections had no trench. Roadkills were counted at all sites over 20 days before the trench was dug and 20 days afterwards, by an observer in a car moving at 40–50 km/h.

5.6. Install fences around existing culverts or underpasses under roads/railways

73https://www.conservationevidence.com/​actions/​2525

74Four studies evaluated the effects on mammals of installing fences around existing culverts under roads/railways. Two studies were in the USA1,2 one was in Portugal3 and one was in South Africa4.

75COMMUNITY RESPONSE (0 STUDIES)

76POPULATION RESPONSE (3 STUDIES)

77Survival (3 studies): Two out of three before-and-after studies (including a controlled and a site comparison study), in the USA1, Portugal3 and South Africa4, found that installing or enhancing roadside fencing alongside existing culverts reduced mammal road mortality whilst one study found that such fences did not alter mammal road mortality.

78BEHAVIOUR (1 STUDY)

79Use (1 study): A replicated, randomized, controlled, before-and-after study in the USA2 found that fences installed to funnel animals to existing culverts did not increase culvert use by bobcats.

Background
Culverts are often installed under roads to aid or enable drainage whilst underpasses enable movement of traffic or apparatus such as farming machinery. Such passages are sometimes used by animals to make road crossings but many animals may nonetheless cross over the road surface and are then at risk of collision with vehicles. This intervention includes studies where fences are installed or extended specifically in a way designed to encourage animals to use existing passages rather than crossing over the road surface. It includes only studies that specifically assess the effectiveness of fencing in a way that can be separated from that of underpasses. For situations where roadside fencing is installed specifically to prevent animal access to roads, in some cases along with underpasses as part of an integrated road casualty reduction scheme, see Install barrier fencing along roads. See also
Install barrier fencing and underpasses along roads for studies that assess the combined effectiveness of installing fending and underpasses.
See also:
Install tunnels/culverts/underpass under railways and Install tunnels/culverts/underpass under roads.

  • 40 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyom (...)

80A before-and-after study in 1976–1981 along a highway through shrubland in Wyoming, USA40 found that after a fence alongside the highway that was connected to underpasses was made taller, fewer mule deer Odocoileus hemionus were killed. Results were not tested for statistical significance. In six migration seasons (three springs, three autumn–winters) after increasing the height of the fence, only one deer-vehicle accident occurred in the fenced area. In three migration seasons before fence construction (two spring and one autumn–winter), 53 deer–vehicle accidents occurred within the area to be fenced. The study was conducted along a stretch of highway constructed in late 1970. In 1977–1978, the height of a fence along the highway was increased from 4 ft to 8 ft along both sides of 7.8 miles of road. The fence allowed deer to access seven underpasses (length: 110–393 feet; width: 10–50 feet; height: 10–17 feet). Deer movement was monitored before (1976–1977) and after (1978–1981) fence heightening by direct observation, track counts, radio-tracking and automatic cameras. The highway was located across a migration route of 1,600–2,000 mule deer.

  • 41 Cain A.T., Tuovila V.R., Hewitt D.G. & Tewes M.E. (2003) Effects of a highway and mitigation projec (...)

81A replicated, randomized, controlled, before-and-after study in 1997–1999 in dry shrubland along a highway in Texas, USA41 found that installing fences to funnel animals to existing culvert entrances did not increase culvert use by bobcats Lynx rufus. Fences did not significantly increase cat spp. use of culverts (data not presented). However, among four culverts most used by bobcats, two fenced culverts saw a rise in use after fence installation (after 7.2; before: 3.9 track sets/month) while two unfenced culverts saw a fall over this same time (after: 2.2; before: 2.9 track sets/month). Most cats (371 of 471 camera-trap images) were bobcats. The remainder were feral cats Felis catus. At six culverts, randomly selected from 12, wire net fences (1.6 m high) were erected at entrances, extending 100 m to each side, parallel to the road. Culverts were checked two times/week from 1 July 1997 to 31 May 1999 for cat spp. tracks. Remote cameras were used at culverts from 1 August 1997 to 31 May 1999. Fences were erected after the first year of monitoring.

  • 42 Villalva P., Reto D., Santos-Reis M., Revilla E. & Grilo C. (2013) Do dry ledges reduce the barrier (...)

82A replicated, before-and-after, site comparison study in 2008–2009 of 64 culverts under roads in southern Portugal42 found that fences connecting to existing under-road culverts did not alter mammal road mortality. After fence installation, there was a similar number of mammals killed by traffic (19 road-kills) compared to before (20 roadkills). There was also no significant difference in mammal road-kills between road sections where fences were installed (19 road-kills) and those that were not fenced (13 road-kills). In April 2008, 100-m-long fences with 2.5-cm mesh, buried to 50 cm deep and extending 50 cm above ground, were installed alongside the road at each side of 32 under-road culverts. These were in addition to existing livestock fencing. Another 32 culverts in the same area that were unfenced were selected for comparison. The number of mammals killed by traffic was recorded by highway maintenance staff for 10 months before and 10 months after fence installation.

  • 43 Collinson W.J., Davies-Mostert H.T. & Davies-Mostert W. (2017) Effects of culverts and roadside fen (...)

83A randomized, replicated, controlled, before-and-after study in 2015 along a road through dry savanna in Limpopo, South Africa43 found that installing fences around existing culverts reduced mammal road casualties. Results were not tested for statistical significance. One scrub hare Lepus saxatilis was detected as a roadkill near fenced culverts compared to two bushveld gerbils Tatera leucogaster detected as roadkills before fencing was installed. Concurrently, two multimammate rats Mastomys sp. were detected as roadkills near unfenced culverts after fence installation at treatment sites compared to one before fence installation. The study was conducted along six 400-m-long road segments with culverts. In three segments, a 70-cm-high fence was erected extended 200 m along both sides of the road on either side of the culvert. The fence was approximately 2 m from the road verge, sloped at 45° away from the road and extended 30 cm below ground. Three segments remained unfenced. Roadkills were counted in all sites during a 20-day period before fences were installed (January 2015) and a 20-day period after (February 2015). Roadkills were counted by an observer in a car moving at 40–50 km/h.

5.7. Install overpasses over roads/railways

84https://www.conservationevidence.com/​actions/​2526

85Twenty-two studies evaluated the effects on mammals of installing overpasses over roads or railways. Seven studies were in Canada1,4,6,7,18,20,22, three were in Spain2,8,11, three were in Australia10,14,19, two were in Sweden12,13, one each was in the Netherlands5, Germany15, Croatia16 and the USA21, and three (including two reviews) were conducted across multiple countries3,9,17.

86COMMUNITY RESPONSE (0 STUDIES)

87POPULATION RESPONSE (4 STUDIES)

88Survival (4 studies): Four studies (including three before-and-after studies), in Canada4, Sweden12,13 and Australia14, found that overpasses (in combination with roadside fencing) reduced collisions between vehicles and mammals. In two of these studies, data from overpasses and underpasses were combined for analysis4,14.

89BEHAVIOUR (21 STUDIES)

90Use (21 studies): Nineteen studies, in North America1,6,7,18,20,21,22, Europe2,3,5,8,11,12,13,15,16 and Australia10,14,19, found that overpasses were used by mammals. A wide range of mammals was reported using overpasses, including rodents and shrews1,5,6,8,11,20, rabbits and hares2,8,11,16, carnivores2,5,7,8,11,15,15, ungulates3,5,7,8,10,11,12,13,16,21, bears7,16,18,22, marsupials10,14,19 and short-beaked echidna10. A review of crossing structures in Australia, Europe and North America17 found that overpasses were used by a range of mammals, particularly larger mammal species. A global review of crossing structures (including overpasses)9 found that all studies reported that the majority of crossings were used by wildlife.

Background
Wildlife overpasses are constructed to provide safe road and rail crossing opportunities for wildlife. A range of different structures can be used as overpasses including purpose-built ‘green bridges’, on which natural vegetation is established, through to multi-use crossings that are accessible to wildlife. Overpasses are often used in combination with wildlife barrier fences that prevent animals accessing the road and which funnel animals toward the overpasses (see
Install barrier fencing along roads and Install barrier fencing along railways). Studies summarised within this intervention cover both overpasses created specifically for wildlife and those that were created for other purposes but where information about use of such structures by mammals is included. Studies mostly report on the use of such structures, such as the number of crossings made, rather than on wider population-level effects of their presence.
See also:
Install tunnels/culverts/underpass under railways and Install tunnels/culverts/underpass under roads.

  • 44 Doucet G.J., Sarrazin J. & Bider J-P.R. & Bider R. (1974) Use of highway overpass embankments by th (...)

91A replicated study in 1971–1973 of 21 highway overpasses constructed for wildlife use in Québec and Ontario, Canada44 found that they were extensively used by woodchucks Marmota monax. Woodchucks or their burrows were recorded on 18 of 21 overpasses surveyed. Across four surveys on overpasses, minimum total woodchuck numbers were 16–22. On average, underpasses had 45 woodchucks/100 acres, a high figure compared to those reported by other authors in open flat ground. Twenty-one highway overpasses were built up with rubble and sand and covered with topsoil. Four overpasses had an average area of 72,000 square feet. Overpasses were surveyed once in 1971, twice in 1972 and once in 1973. Surveys were conducted in May, when grass (mainly Agropyron repens) was short. Animals and burrows on overpasses were counted from a vehicle (first two surveys) and on foot (last two surveys).

  • 45 Rodriguez A., Crema G. & Delibes M. (1996) Use of non-wildlife passages across a high speed railway (...)

92A study in 1991–1992 along a high-speed railway within agricultural land in Castilla La Mancha, Spain45 found that two flyovers not designed for wildlife were used to cross the railway by small mammals, but not by deer or wild boar Sus scrofa. Small mammals were recorded, with data combined between two overpasses and 15 underpasses, 582 times (37/100 passage-days) and brown hare Lepus granatensis and European rabbit Oryctolagus cuniculus, 89 times (5/100 passage-days). Tracks of four carnivore species, red fox Vulpes vulpes, wild cat Felis silvestris, common genet Genetta genetta and Iberian lynx Lynx pardinus, were recorded. No deer or wild boar Sus scrofa were recorded using overpasses or underpasses. Two flyovers (small roads) crossing a 25-km section of a high-speed railway were monitored. Sand, 3 cm thick and 1 m wide, was put at one entrance to each. Animal tracks were monitored for 15–22 days/month between September 1991 and July 1992.

  • 46 Keller V. (1999) The use of wildlife overpasses by mammals: results from infrared video surveys in (...)

93A replicated study in 1996 of roads in Germany, Switzerland, France and the Netherlands46 found that mammals used flyovers as bridges/overpasses across roads, and frequency of their use tended to increase with overpass width. For all mammal species, frequency of use of the seven narrow overpasses (<15 m wide) was very low. Roe deer Capreolus capreolus used the nine medium-sized (15–50 m wide) and five wide overpasses (>50 m wide) significantly more frequently than they used narrow overpasses. Twenty-one wildlife flyovers/overpasses, in Germany (eight), Switzerland (six), France (four) and the Netherlands (three), were monitored using infra-red video equipment. Flyover widths were 3.4–186 m. Video surveys were carried out during a total of 223 nights.

  • 47 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicl (...)

94A replicated, before-and-after study in 1981–1999 in temperate mixed woodland and grassland in Alberta, Canada47 found that wildlife overpasses, underpasses and roadside barrier fencing reduced road deaths of large mammals. Species recorded as road casualties included coyote Canis latrans, black bear Ursus americanus, wolf Canis lupus, bighorn sheep Ovis canadensis, moose Alces alces, deer Odocoileus spp. and elk Cervus canadensis. Mammal-vehicle collisions were significantly lower during the two years after fencing (5–28/year) compared to the two years before (18–93/year) for all three road sections, despite an increase in traffic flow. Ungulate casualties declined by 80 %. Most road deaths were within 1 km of the end of the fences. Deaths also occurred close to drainage structures. The Trans-Canada highway was expanded to four lanes and had 2.4-m-high wildlife exclusion fence installed in three phased sections, completed in 1984 (10 km), 1987 (16 km) and 1997 (18 km). In addition, 22 wildlife underpasses and two overpasses were constructed. Wildlife-vehicle collisions were monitored from May 1981 to December 1999.

  • 48 van Wieren S.E. & Worm P.B. (2001) The use of a motorway wildlife overpass by large mammals. Nether (...)

95A study in 1989 and 1994–1995 along a motorway between Arnhem and Apeldoorn in the Netherlands48 found that a wildlife overpass was used by deer, wild boar Sus scrofa, rodents and carnivores. The overpass was used most frequently by red deer Cervus elaphus (1989: 0.1–9 crossings/night; 1994–1995: 4–21) and wild boar (1989: 0.5–21; 1994–1995: 0.5–8.5). It was used less often by roe deer Capreolus capreolus (1989: 2.0 crossings/night; 1995–1994: 0.5) and fallow deer Dama dama (data not presented). Twenty-five rodents and shrews, of three species, wood mouse Apodemus sylvaticus, common vole Microtus arvalis and common shrew Sorex aranaeus, were caught on the overpass. Overpasses were also used by badger Meles meles and red fox Vulpes vulpes. Overall numbers of crossings was greater in 1994–1995 than 1989 (16 vs 12 crossings/night). The overpass was constructed in the late 1980s. It was 50 m wide, 95 m long and planted with trees. Large mammal tracks were recorded on a 5-m-wide sand strip across the overpass, on 93 occasions in 1989 and 114 occasions in May 1994–April 1995. Small mammals were caught during five nights in summer 1995 using 20 live traps at each end and 32 mouse-traps between.

  • 49 McDonald W. & St Clair C.C. (2004) Elements that promote highway crossing structure use by small ma (...)

96A replicated study in 1999–2000 in Alberta, Canada49 found that deer mice Peromyscus maniculatus, but not red-backed voles Clethrionomys gapperi or meadow voles Microtus pennsylvanicus, crossed wildlife overpasses. Forty percent of deer mice translocated across roads crossed back over when released alongside overpasses, but no voles did. More animals successfully returned through overpasses (and underpasses) with 100 % vegetation cover at entrances (55–100 % of animals) compared to those with 50 % cover (20–76 % of animals) or no cover (0–66 % of animals). Those animals that crossed did so in 1–4 days. Two sparsely vegetated wildlife overpasses (75–79 m long, 15 m wide) were used. Territorial mice and voles were caught using Longworth live traps (166 caught in total), ear-tagged, coated with fluorescent powder, translocated across the road, released 2 m from overpasses (or underpasses) and followed as they returned. The amount of ground cover 2 m inside and outside entrances was manipulated to 100 %, 50 % and no cover, using spruce branches. Traps at original capture sites were monitored for four days after translocation. Animals that did not return were returned by hand. Monitoring was undertaken in July–October 1999 and 2000.

  • 50 Clevenger A.P. & Waltho N. (2005) Performance indices to identify attributes of highway crossing st (...)

97A study in 1997–2000 in Alberta, Canada50 found that large herbivores and carnivores used two wildlife overpasses. A total of 640 visits to overpasses by elk Cervus canadensis, 1,086 by deer Odocoileus spp., 10 by black bear Ursus americanus, nine by grizzly bear Ursus arctos, eight by wolf Canis lupus and 12 by cougar Puma concolor were recorded, with the majority involving animals crossing the structures. Features that positively influenced use of crossings (two overpasses and 11 underpasses) included increased width, height and openness. Black bears and cougars, though, favoured more constricted crossing structures. Increased length and noise negatively influenced use of crossing structures for some species. Two 50-m-wide overpasses were monitored along an 18-km-stretch of the four-lane Trans-Canada Highway. Barrier fencing, 2.4-m-high, ran alongside the highway. Tracks were monitored at each end of each overpass (in 2 × 4 m of sand/clay), every 3–4 days, from November 1997 to August 2000. Infra-red activated cameras were also used. Information about structure, landscape and human activity were recorded for each overpass.

  • 51 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2005) Complementary use by vertebrates of cr (...)

98A study in 2002 in along a road in Zamora, Spain51 found that wildlife overpasses were used by mammals. Overpasses were used by red deer Cervus elaphus (detected at wildlife overpasses on average of 2/10 days), small mammals (shrews, mice and voles; detected 1.0/10 days) and rabbits and hares (detected 4.5/10 days). Other overpasses, such as rural tracks, were used by small mammals (detected 6.4/10 days), rabbits and hares (3.3/10) and foxes Vulpes vulpes (1.4/10), but not by red deer. Two wildlife overpasses (16 m wide, 60 m long) and 16 general overpasses (rural tracks, 7–8 m wide, 58–62 m long) were monitored along a 72-km section of the A-52 motorway. The motorway had barrier fencing along its length. Marble dust (1 m wide cross) was used to record animal tracks for 10 days in June–September 2002. Camera traps were installed on some overpasses.

  • 52 van der Ree R., van der Grift E., Mata C. & Suarez F. (2007) Overcoming the barrier effect of roads (...)
  • 53 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2005) Complementary use by vertebrates of cr (...)
  • 54 Goldingay R.L., Taylor B.D. & Ball T. (2011) Wooden poles can provide habitat connectivity for a gl (...)

99A global review in 2007 of 123 studies investigating the use of wildlife crossings52 found that all studies reported that the majority of underpasses and overpasses were used by wildlife. A total of 1,864 structures were reported on, mainly underpasses (83 %; including culverts (742 examples), bridges (130), tunnels (340) and unknown types (333)). Overpasses included land bridges (68), overpasses with small roads (112), canopy bridges53, glider poles54 and others (35). Structures provided crossings over or under roads (113 studies), railways (5 studies), both (1 study), canals (2 studies) and a pipeline (1 study). Studies were from Europe (55 studies), the USA (30 studies), Canada (nine studies), South America (one study) and Australia (29 studies).

  • 55 Bond A.R. & Jones N.J. (2008) Temporal trends in use of fauna-friendly underpasses and overpasses. (...)

100A study in 2004–2007 in eucalypt woodland in Queensland, Australia55 found that a wildlife bridge was used by mammals. A total of 1,240 herbivore scats were recorded on the bridge. Brown hare Lepus capensis scats were the most common (78 %), followed by red-necked wallaby Macropus rufogriseus (15 %), eastern grey kangaroo Macropus giganteus (5 %), swamp wallaby Wallabia bicolor (1 %), possum (1 %) and short-beaked echidna Tachyglossus aculeatus (1 %). Six mammals were killed on the road before construction and one afterwards. In 2004, a 1.3-km section of highway was upgraded to four lanes and a variety of wildlife crossings constructed, with barrier fencing (2.5 m high) between. Use of a large overpass (15–20 m wide, 70 m long, planted with grass, shrubs and trees) was monitored from six months after completion. Scats were recorded weekly from August 2005–February 2006 and for two weeks in June 2007. Road-kill was monitored twice weekly before construction (April–July 2004) and weekly afterwards, until June 2007.

  • 56 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2008) Are motorway passages worth building? (...)

101A replicated study in 2001 in Zamora province, Spain56 found that overpasses were used by mammals. Wildlife overpasses were used by red fox Vulpes vulpes (detected on average per overpass on 3.5/10 days), wild boar Sus scrofa (2.3/10 days), small mammals (shrews, mice and voles; 0.3/10 days) and rabbits and hares (3.0/10 days). Other overpasses, such as rural tracks, were also used by wild boar (detected on average per crossing on 0.7/10 days), small mammals (1.0/10 days), rabbits and hares (1.8/10 days), red deer Cervus elaphus (0.2/10 days), rats Rattus sp. (1.3/10 days), western hedgehogs Erinaceus europaeus (0.2/10 days), European badger Meles meles (0.2/10 days) and red fox (3.0/10 days). Cat and dog prints were also detected but could not be determined as being from either wild or domestic species. Overall, overpasses (not including wildlife overpasses) were used disproportionately more than were other crossings (which included underpasses and culverts — data presented as indices). Four wildlife overpasses (15–20 m wide, 60–62 m long) and six general overpasses (rural tracks, 7–8 m wide, 58–65 m long) were monitored along the A-52 motorway. The motorway had barrier fencing along its length. Marble dust (1-m-wide cross) was used to record animal tracks daily for 10 days in March–June 2001.

  • 57 Olsson M.P.O. & Widen P. (2008) Effects of highway fencing and wildlife crossings on moose Alces al (...)

102A before-and-after study in 2002–2004 in mixed forest and farmland in southwestern Sweden57 found that following installation of two wildlife overpasses and barrier fencing, moose Alces alces used overpasses and collisions with vehicles decreased, but fencing created a barrier to movements. There were fewer moose-vehicle collisions after overpass and fence construction (zero/year) than before (2.7/year). During construction, 1.8 collisions/year were recorded. Moose were recorded crossing the highway 12 times after overpass and fence installation (during 18 months) and 47 times before installation (eight months). All crossings after construction were via the two wildlife overpasses. Home-range locations changed significantly, with ranges intersected by the highway decreasing to five out of 38 monitored ranges (13 %) after fencing from 10 out of 38 (26 %) before. Two 6-km sections of the European highway 6 were converted to a fenced four-lane highway in 2000–2004. A third section remained unfenced (3 km). The sections contained two wildlife overpasses, one wildlife underpass, three conventional road tunnels and two conventional bridges that could be crossed. Twenty-four moose were radio-collared. Locations were recorded every two hours before construction (February–September 2002), during construction (October 2002–May 2004) and after construction (June 2004–December 2005).

  • 58 Olsson M.P.O., Widen P. & Larkin J.L. (2008) Effectiveness of a highway overpass to promote landsca (...)

103A before-and-after study in 2000–2005 in forest and farmland in southwestern Sweden58 found that a wildlife overpass was used by moose Alces alces and roe deer Capreolus capreolus and, along with barrier fencing, it reduced road-kills. Deaths were reduced 70 % from the 12-year pre-construction averages of 2.7 moose killed/year and 5.3 roe deer killed/year. From March 2002–June 2005, the overpass was crossed 437 times by roe deer and 95 times by moose (mainly at night). Roe deer, but not moose crossings, increased over the six-year study. Five to seven individual moose/year used the overpass. Overpass use declined with increased traffic flow. In 2000–2004, a 12-km section of the European Highway 6 was converted from two to four lanes and 2.2-m-high exclusion fencing was installed. Two overpasses and one underpass were constructed. One hourglass-shaped overpass (29–17 m wide, 80 m long, 2 m high, with grey glass-shields to reduce incursion of highway noise and light) was monitored. Tracks were counted in sand beds twice/week and two infrared remote cameras were set overnight. Twenty-four moose were tracked using GPS collars for 22 months.

  • 59 Hayes I. & Goldingay R.L. (2009) Use of fauna road-crossing structures in north-eastern New South W (...)

104A site comparison study in 2006 along a highway in New South Wales, Australia59 found that two wildlife overpasses were used by mammals and presence of crossing-structures along with roadside fencing reduced road-kills. There were fewer road-kills over seven weeks along the section with crossing-structures (0.02/km) than along a section without crossings (0.07/km). The most frequently recorded road casualties along both sections combined were bandicoots (16 casualties) and kangaroo and wallabies (nine casualties). Kangaroos and wallabies used the two overpasses more than they used two underpasses (104 vs 36 tracks). However, the overpasses were used less than were underpasses by bandicoots (28 vs 87) and rodents (15 vs 82). Use was similar for possums (overpasses: 9; underpasses: 14). There were two wildlife bridges (9–37 m wide, with vegetation) and two concrete box culverts (3 × 3 m, 42–63 m long), with 5 km of exclusion fencing, along a 12-km section of dual-carriageway highway. Tracks were monitored on sand plots across each crossing. Road-kill surveys were conducted along the 12-km section and along a 51-km two-lane section without crossings or fencing. Track and road-kill surveys were conducted up to three times/week over seven weeks in August–September 2006.

  • 60 Klar N., Herrmann M. & Kramer-Schadt S. (2009) Effects and mitigation of road impacts on individual (...)

105A study in 2001–2005 along a motorway through forest and agricultural land in Germany60 found that most overpasses, viaducts and underpasses were used by wildcats Felis silvestris to cross roads. Wildcats used crossing structures on 18 of 21 (85 %) of the occasions in which they were recorded <50 m from the motorway. Open-span viaducts were used by the highest proportion of cats (five out of seven for which viaducts fell within their home ranges). Forest road overpass were used by one out of eight cats for which road overpasses fell within their home ranges. Two open-span viaducts (335–660 m wide, 29 m long), two forest road overpasses (6 m wide, 46–61 m long) and three underpasses were monitored in 2002–2005. Twelve wildcats were radio-collared between January 2001 and February 2005. Animals were tracked at night for 3–30 months each, to monitor their road crossings.

  • 61 Kusak J., Huber D., Gomerčić T., Schwaderer G. & Gužvica G. (2009) The permeability of highway in G (...)
  • 62 Rodriguez A., Crema G. & Delibes M. (1996) Use of non-wildlife passages across a high speed railway (...)
  • 63 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicl (...)
  • 64 Doucet G.J., Sarrazin J. & Bider J-P.R. & Bider R. (1974) Use of highway overpass embankments by th (...)

106A study in 1999–2003 along a road through beech and fir forest in Gorski kotar, Croatia61 found that medium-large mammals used a wildlife overpass (a green bridge) and two other overpasses not specifically designed for wildlife. Monitoring of the green bridge revealed tracks of hare Lepus europaeus (49 tracks), wild boar Sus scrofa (66), roe deer Capreolus capreolus (166), red deer Cervus elaphus (103), fox Vulpes vulpes (83), badger Meles meles 62, brown bear Ursus arctos (39), grey wolf Canis lupus 63and Eurasian lynx Lynx lynx 64. A similar range of species was recorded on the two other overpasses that were not designed as green bridges (see paper for data). A new highway was constructed in 1998–2004, with 2.1-m barrier fencing. Along a 9-km section, a 100-m-wide green bridge and two overpasses (742 and 835 m wide) above road tunnels, were monitored. Tracks (in snow, mud or sand) and other animal signs were counted 64 times at the green bridge and eight and 23 times at the two other overpasses, in January 1999–January 2001. One of the overpasses was also monitored using a camera trap.

  • 65 Taylor B.D. & Goldingay R.L. (2010) Roads and wildlife: impacts, mitigation and implications for wi (...)

107A review of 30 papers monitoring 329 crossing structures in Australia, Europe and North America65 found that overpasses were used by a range of mammals, particularly larger mammal species. Small mammals used conventional bridge overpasses (demonstrated by 2/4 relevant studies) and wildlife overpasses (4/7 studies). Arboreal mammals used wildlife overpasses (1/1 study). Medium-sized mammals used conventional bridge overpasses (4/5 studies) and wildlife overpasses (5/7 studies). Large mammals used conventional bridge overpasses (9/11 studies) and wildlife overpasses (23/23 studies). Studies suggested that ungulates used overpasses more when they were close to vegetation cover and a river or stream and less when they were in a cropland area. Narrow overpasses (<6 m wide) were not used by deer. Thirty papers, monitoring 329 crossing structures, were reviewed. Fourteen papers investigated multiple structure types, resulting in a total of 52 studies of different structure types. Overpasses included land bridges, wildlife overpasses with grass, trees or other vegetation, combined wildlife and vehicle overpasses, pole bridges and rope bridges.

  • 66 Sawaya M.A., Clevenger A.P. & Kalinowski S.T. (2013) Demographic connectivity for ursid populations (...)

108A replicated study in 2006–2008 of two overpasses over a highway in a Natural Park in Alberta, Canada66 found that American black bears Ursus americanus and grizzly bears Ursus arctos used the overpasses. Over three years, a total of eight passages of American black bears (by one individual at each overpass) and 210 of grizzly bears (by 10 individuals at each overpass) were detected. Bear crossings were monitored at two overpasses (dimensions not stated) in Bow Valley, Banff National Park. Overpasses were built in the 1980s and 1990s, and cost >US$2 million each to construct. Bear tracks were counted in May– October 2006, April–October 2007 and April–October 2008 using track pads comprising 1.5–2 m of sandy loam. Track pads were checked every two days and the species, direction of travel, and number of animals was recorded. Individuals were identified by DNA analysis of hairs caught on barbed wires on overpasses.

  • 67 Bond A.R. & Jones D.N. (2014) Roads and macropods: interactions and implications. Australian Mammal (...)

109A review of two studies in 2006–2008 in Australia67 found that overpasses installed over roads were used by eastern grey kangaroos Macropus giganteus, red-necked wallabies Macropus rufogriseus and swamp wallabies Wallabia bicolor. All road overpasses used fencing to reduce likelihood of animals crossing roads rather than using overpasses. Overpasses in the review were 70 m long and 15 m wide.

  • 68 D’Amico M., Clevenger A.P., Román J. & Revilla E. (2015) General versus specific surveys: Estimatin (...)

110A replicated study in 2009 at two sites along a highway through forest in Alberta, Canada68 found that North American deer mice Peromyscus maniculatus, southern red-backed voles Myodes gapperi and meadow voles Microtus pennsylvanicus used overpasses to cross a road. Deer mouse tracks were recorded in 75 % of track tubes established on overpasses. Southern red-backed vole tracks were detected in 15 % and meadow vole in 5 % of track tubes. Over two weeks in September– October 2010, small mammals were surveyed on two 50-m-wide wildlife overpasses above the Trans-Canada Highway. Overpasses consisted of sparse young trees, shrubs and open grassland. Two parallel sample lines, each with five 30 cm long × 10 cm diameter track tubes, with sooted metal sheet as a floor, were placed in the centre of each overpass. Mammals were identified from their footprints.

  • 69 Simpson N.O., Stewart K.M., Schroeder C., Cox M., Huebner K. & Wasley, T. (2016) Overpasses and und (...)

111A replicated study in 2010–2014 of five crossing structures at two sites along a highway in Nevada, USA69 found that more migratory mule deer Odocoileus hemionus used overpasses than underpasses to cross a road. More mule deer crossed the road across two overpasses (234–4,007 deer crossings/overpass/season) than through three underpasses (44–629 deer crossings/underpass/season). Crossing structures, 1.5–2.0 km apart, were located at important crossings for migratory deer. One site had one overpass and two underpasses. The other had one of each structure. Overpasses, made of concrete arches, were 31–49 m wide and 8–20 m long. Cylindrical underpasses were 8 m wide, 28 m long and 6 m tall. All structures had soil bases. Fencing, 2.4 m high, deterred deer from accessing the highway between crossings and extended 0.8–1.6 km beyond crossings at each site. Crossings were monitored, during six to eight mule deer migratory periods (between autumn 2010 and spring 2014) using camera traps, over 10 weeks in each migration (15 September to 1 December and 1 March to 15 May). Cameras were positioned 12 m apart along crossing structures.

  • 70 Ford A.T., Barrueto M. & Clevenger A.P. (2017) Road mitigation is a demographic filter for grizzly (...)

112A study in 1996–2014 of 18 overpasses and 19 culverts crossing a major highway in Alberta, Canada70 found that overpasses were used by grizzly bears Ursus arctos, particularly in family groups. Over an 18-year period, grizzly bears used overpasses more often (241 crossings/ structure) than they used culverts (122 crossings/structure). Over an eight-year period, bear family groups used overpasses more often (1.4 family groups/year/structure) than they used culverts (0.0–0.3 family groups/year/structure). In 1996–2006, 2-m-wide pads, were covered in sandy-loam soil to survey bear movements at 23 crossing structures. From 2008, remote cameras were installed at all crossing structures. As more crossing structures were built in the area, they were added to the survey, up to a maximum of 18 overpasses and 19 culverts. It is not clear when these structures were built.

5.8. Install pole crossings for gliders/flying squirrels

113https://www.conservationevidence.com/​actions/​2546

114Seven studies evaluated the effects on gliders/flying squirrels of installing pole crossings. Six studies were in Australia1,2,4–7 and one was in the USA3.

115COMMUNITY RESPONSE (0 STUDIES)

116POPULATION RESPONSE (1 STUDY)

117Survival (1 study): A study in Australia7 found that arboreal marsupials using artificial road crossing structures did not suffer high predation rates when doing so.

118BEHAVIOUR (6 STUDIES)

119Use (6 studies): Six studies (five replicated), in Australia1,2,4,5,6 and the USA3, found that poles were used for crossing roads by squirrel gliders1,2,4,5,6, sugar gliders6 and Carolina northern flying squirrels3.

Background
Wildlife crossings over or under roads may be installed to reduce the impact of the road on animal mortality and on habitat fragmentation. They usually take the form of tunnels or bridges of a range of designs. These may not be suitable for use by mammals that move by gliding from tree to tree. Glide poles have been trialled, especially in Australia (e.g. Ball & Goldingay 2008), to provide a means of reconnecting habitat and reducing road mortality for gliding mammal species. Monitoring typically takes the form of documenting use of poles rather than looking at population level effects or impacts on road mortality.
See also:
Install rope bridges between canopies.

120Ball T.M. & Goldingay R.L. (2008) Can wooden poles be used to reconnect habitat for a gliding mammal? Landscape and Urban Planning, 87, 140–146, https://doi.org/​10.1016/​j.landurbplan.2008.05.007

  • 71 Goldingay R.L., Taylor B.D. & Ball T. (2011) Wooden poles can provide habitat connectivity for a gl (...)

121A replicated study in 2006–2010 of a pasture and two highways through a woodland in Queensland, Australia71 found that lines of poles were used by squirrel gliders Petaurus norfolcensis to cross the gaps between trees. At the pasture site, squirrel gliders were detected on all five surveys of poles. At the highway crossing sites, gliders were detected on 25 out of 30 and 11 out of 16 surveys of poles. Summing records for each pole in each monitoring session, gliders were recorded on 13/20 poles at the pasture site and 130/240 and 32/114 poles at highway sites. Canopy gaps of 50–70 m were spanned by 5–8 poles, 5–12 m high and 5–22 m apart. One pole line was across a pasture and two were over existing wildlife bridges across highways. Poles had crossbars attached close to the top. Squirrel glider usage of poles was assessed using hair tube surveys between October 2006 and April 2010.

  • 72 Taylor B.D. & Goldingay R.L. (2012) Restoring connectivity in landscapes fragmented by major roads: (...)

122A replicated, site comparison study in 2006–2010 at four sites along two roads through forests in New South Wales and Queensland, Australia72 found that glider poles along overpasses were used by squirrel gliders Petaurus norfolcensis for crossing roads. Gliders used glider poles along both overpasses where they were installed (detected on 30–66 % of sample sessions). No gliders were detected in the middle of either overpass that did not have glider poles. Two overpasses (36–70 m long, 10–15 m wide, constructed in 2005–2008), each had eight glider poles installed. Poles were 6.5 m high and 5–12 m apart. Two further overpasses (62–66 m long, 19–37 m wide, constructed in 2002) had no poles. Between September 2006 and December 2010, gliders were surveyed 23–35 times at each site with poles, using hair-traps attached 1.8 m high on each pole. Overpasses without poles were surveyed 10 times, for 2–4 weeks each time, between May 2010 and June 2011, using six hair-traps/overpass, mounted 1.8 m high on trees or shrubs.

  • 73 Kelly C.A., Diggins C.A. & Lawrence A.J. (2013) Crossing structures reconnect federally endangered (...)

123A replicated study in 2008–2010 at three sites along a road through forest in North Carolina, USA73 found that crossing poles were used by Carolina northern flying squirrels Glaucomys sabrinus coloratus to cross the road. All three radio-tagged flying squirrels crossed the road with at least one using a crossing pole. Out of 25 videos of flying squirrels at crossing poles, 14 (56 %) showed crossing attempts (landing on the opposite pole was not confirmed). In June 2008, six wooden poles (32 cm diameter) were set in three pairs on opposite sides of a two-lane road. Poles, 15 m apart, were buried 2.4 m into the ground and extended 14.3 m above ground. Each pole was fitted with a 3-m-long, 10 × 19-cm horizontal wooden launch beam at the top. In March 2009, three flying squirrels were fitted with radio-transmitters and released onto a crossing pole on the opposite side of the road from their capture location. They were tracked at least monthly between March–June 2009. Infrared motion detection cameras were used at each pole between March 2009 and June 2010 to detected crossings.

  • 74 Soanes K., Lobo M.C., Vesk P.A., McCarthy M.A., Moore J.L. & van der Ree R. (2013) Movement re-esta (...)

124A replicated, site comparison study in 2007–2011 along a highway in Victoria, Australia74 found that glider poles, along with canopy rope bridges across highways, were used occasionally by squirrel gliders Petaurus norfolcensis. Just one of seven radio-tracked squirrel gliders crossed the road where a glider pole was present compared to three of seven crossing canopy road bridges. Seven of 10 crossed a narrow single-lane-road without crossing structures but none of 12 crossed a wider highway with no crossing structures. Camera traps recorded 13 crossings by squirrel gliders at glider poles over 146 camera-trap nights. In July 2007, three glider poles and two rope bridges were installed along a 70-km-long section of four-lane divided highway. Poles (13 m high, 45 cm diameter) were installed in the centre of the highway to reduce glide distances required for road crossings. Camera traps monitored pole use (December 2009–March 2011; 22–87 nights/pole) and rope-bridge use (August 2007–May 2011; 787–873 nights/bridge). In 2010–2011, 42 gliders were radio-tracked at sites with and without crossings and at a narrow (<10 m wide) single-lane road.

  • 75 Taylor B.D. & Goldingay R.L. (2013) Squirrel gliders use roadside glide poles to cross a road gap. (...)

125A study in 2011–2012 at a site on a highway through woodland in Queensland, Australia75 found that roadside glide poles were used by squirrel gliders Petaurus norfolcensis to cross the highway. Squirrel gliders were recorded on poles on 60 out of 310 nights monitored. Road crossings were confirmed on 16 nights of 125 when both sides were monitored. Three poles were installed across a 61-m-wide canopy gap. One pole was on each roadside. A third bridged a 35-m gap between the roadside and forest. The two poles at each side of the gap were thus 6 and 14 m from tree canopies. Poles, made from hardwood, were 30 cm diameter and 12 m high. Wooden crossbars were attached at 20 and 40 cm below the top. Squirrel gliders were monitored using a camera trap on the middle pole from 1 August 2011 to 30 June 2012 and an additional camera trap on the pole across the road from 27 February to 30 June 2012.

  • 76 Soanes K., Vesk P.A. & van der Ree R. (2015) Monitoring the use of road-crossing structures by arbo (...)

126A replicated study in 2012–2014 at 15 sites along a highway though eucalyptus forest in Victoria, Australia76 found that squirrel gliders Petaurus norfolcensis and sugar gliders Petaurus breviceps used glider poles to cross the road. Remote cameras detected 842 road crossings by squirrel gliders and 258 by sugar gliders using glider poles. The study was conducted in two sections of the Hume Freeway, located 200 km apart. In 2007–2009, fifteen pole crossings (≤5 poles/site) were erected spanning roads of 56–382 m wide. Poles were 13–18 m tall, 40–50 cm diameter and made of hardwood timber. A timber cross-beam (10 cm × 10 cm × 2.4 m) was fixed horizontally 0.5 m from the top of each pole (oriented parallel to the road edge). The number and height of poles used in each array varied with gap width and the height of roadside trees. Wildlife crossings were monitored from between April and June 2012 to February 2013, using motion-triggered cameras.

  • 77 Soanes K., Mitchell B. & van der Ree R. (2017) Quantifying predation attempts on arboreal marsupial (...)

127A study in 2007–2015 at five points along a highway through woodland in Victoria, Australia77 found that arboreal marsupials using artificial road crossing structures did not suffer high predation rates when doing so. Among 13,488 detections of arboreal marsupials using glider pole crossings and rope bridges combined (separate figures not given in paper), there were no recorded instances of attempted predation of those using glider poles. One unsuccessful predation attempt was recorded from a rope bridge. In July 2007, five crossing structures were installed along 70 km of highway. Three were poles for gliders (one or two poles/crossing, 12–14 m tall) and two were rope mesh canopy bridges (70 m long, 5 m wide). Crossings were monitored with motion and heat activated cameras from July 2007 to February 2015. Cameras recorded 5–10 images, 3 s apart (2007–2011) or a 10–20 s video (2011–2015). Predation attempts were detectable when animals were ≤1 m from the top of each glider pole or ≤5 m from each end of a canopy bridge.

5.9. Install rope bridges between canopies

128https://www.conservationevidence.com/​actions/​2556

129Ten studies evaluated the effects on mammals of install rope bridges between canopies. Eight studies were in Australia1–5,7,8,10, one was in Brazil6 and one in Peru9.

130COMMUNITY RESPONSE (0 STUDIES)

131POPULATION RESPONSE (1 STUDY)

132Survival (1 study): A study in Australia10 found that arboreal marsupials using rope bridges did not suffer high predation rates when doing so.

133BEHAVIOUR (9 STUDIES)

134Use (9 studies): Nine studies (including three replicated studies and a site comparison), in Australia1–5,7,8, Brazil6 and Peru9 found that rope bridges were used by a range of mammals. Seven of these studies found between three and 25 species using rope bridges1–4,7, one found that that they were used by squirrel gliders5 and one that they were used by mountain brushtail possums and common ringtail possums but not by koalas and squirrel gliders8. One of the studies9 found that crossing rates were higher over the canopy bridges than at ground level.

Background
Wildlife crossings over or under roads may be installed to reduce the impact of the road on animal mortality and on habitat fragmentation. They usually take the form of tunnels or bridges of a range of designs. These may not be suitable for use by mammals that spend most of their time higher up within trees. Rope bridges have been trialled, especially in Australia, to provide a means of reconnecting habitat and reducing road mortality for arboreal mammal species. Monitoring typically takes the form of documenting use of crossings rather than looking at population level effects or impacts on road mortality.
See also:
Install pole crossings for gliders/flying squirrels.

  • 78 Goosem M., Weston N. & Bushnell S. (2005) Effectiveness of rope bridge arboreal overpasses and faun (...)

135A study in 2000–2002 along a road through highland rainforest in Queensland, Australia78 found that all three rope bridges across the road were used by arboreal marsupials. Across the three rope bridges, six species of possums, Lumholtz’s tree kangaroos Dendrolagus lumholtzi and fawn-footed melomys Melomys cervinipes were recorded, with 5–7 species/crossing recorded. The number of crossings was not documented. In 1995, a canopy bridge tunnel was erected 7 m above a 7-m-wide tree gap over a low-traffic road (4 vehicles/day). The bridge comprised a 50 × 50-cm rope tunnel, 14 m long, made of 10-mm silver rope attached to wooden poles, erected amongst trees on the roadside. In 2000, a 10-m-long, 50-cm-wide rope-bridge was erected 7 m high, spanning a 5-m gap over a forestry track. Additionally, a 25-cm-wide rope ladder was placed initially over the same track, then lengthened and moved in 2001 to span a 14-m-wide gap over a road carrying 150 vehicles/day. Mammal crossings were monitored in 2000–2002, through scat and hair analysis, remote photography and spotlighting surveys.

  • 79 Weston N., Goosem M., Marsh H., Cohen M. & Wilson R. (2011) Using canopy bridges to link habitat fo (...)

136A study in 2000–2010 of four roads through rainforest in Queensland, Australia79 found that all seven rope bridges connecting trees at each side of the road were used and nine mammal species in total were recorded. Of these, five species were directly observed crossing bridges. The remaining four were detected solely by other monitoring methods. Totals of 2–7 species/rope bridge were recorded. No mammals were found dead on roads in the vicinity of rope bridges (though details of searches for casualties are not stated). Seven rope bridges in total were erected at four sites in 1995–2005. Two were rope tunnels, with a square cross-section. The remainder were rope ladders, 0.25–0.5 m wide. Mammal use of bridges was monitored by direct observation by spotlight, faeces collected in nets or funnels below bridges, motion-and heat-sensitive cameras and hair collection using sticky tape.

  • 80 Taylor B.D. & Goldingay R.L. (2012) Restoring connectivity in landscapes fragmented by major roads: (...)

137A site comparison study in 2010–2011 at three overpasses along a road through forest in Queensland, Australia80 found that squirrel gliders Petaurus norfolcensis, a brushtail possum Trichosurus vulpecula and a ringtail possum Pseudocheirus perigrinus used a rope bridge that connected between glider poles across the overpass. Squirrel gliders were detected using the rope bridge on 33 occasions during 27 of 166 survey nights. Over the same period, one brushtail possum and one ringtail possum were detected. No gliders crossed two overpasses that did not have glider poles or rope bridges. The study was conducted on an overpass (36 × 15 m, constructed in 2008) with eight glider poles, 6.5 m high, connected by a single rope (40 mm diameter). Two overpasses without poles or a rope bridge (62–66 m long, 19–37 m wide) were also monitored. Mammal crossings were surveyed using camera traps between September 2010 and April 2011. A camera was placed near the top of one end pole and directed along the connecting rope. Cameras were also placed in the middle of overpasses without poles.

  • 81 Goldingay R.L., Rohweder D. & Taylor B.D. (2013) Will arboreal mammals use rope-bridges across a hi (...)

138A replicated study in 2008–2011 of five rope bridges at four sites along a highway through woodlands in New South Wales, Australia81 found that rope bridges were used by six mammal species. Bridges were used by squirrel gliders Petaurus norfolcensis (44 records at two bridges), feathertail gliders Acrobates pygmaeus (nine records at three bridges), common ringtail possums Pseudocheirus peregrinus (seven records at one bridge), common brushtail possums Trichosurus vulpecula (33 records at two bridges), sugar gliders Petaurus breviceps (15 records at two bridges) and black rats Rattus rattus (19 records at two bridges). Two rope bridges across the highway (42–75 m long) were monitored at one site. Single bridges (each approximately 50 m long), crossing creeks underneath the highway at each of two sites, were monitored. At the fourth site, a rope bridge was suspended from a series of poles along a 70-m-long land bridge over the highway. Sites were up to 270 km apart. Bridges, erected in 2004–2008, comprised rope mesh either laid flat or formed into tunnels. They were monitored by 1–3 camera traps/bridge for 42–503 nights/camera.

  • 82 Soanes K., Lobo M.C., Vesk P.A., McCarthy M.A., Moore J.L. & van der Ree R. (2013) Movement re-esta (...)

139A replicated, site comparison study in 2007–2011 along a highway in Victoria, Australia82 found that canopy rope bridges across highways, along with glider poles, were used by squirrel gliders Petaurus norfolcensis. Three of seven squirrel gliders crossed roads when canopy bridges were present. The proportion of squirrel gliders crossing roads where canopy bridges or glider poles were installed (29 %) was higher than that which crossed roads when such structures were absent (0 %). However more still (70 %) crossed at a narrow, single-lane road with low traffic flows and no artificial crossing structures. Camera traps recorded 1,187 crossings at canopy bridges. It took 9–13 months for gliders to habituate to and use bridges. In July 2007, two rope bridges and three glider poles were installed at five sites along a 70-km-long section of a four-lane divided highway. Canopy rope bridges were 70 m long, 0.5 m wide and 6 m high. Camera traps monitored bridge (August 2007– May 2011; 787–873 nights/bridge) and pole use (December 2009–March 2011; 22–87 nights/pole crossing). In 2010–2011, 42 gliders were radio-tracked at sites with and without crossings and at a single-lane-road site (<10 m wide).

  • 83 Teixeira F.Z., Printes R.C., Fagundes J.C.G., Alonso A.C. & Kindel A. (2013) Canopy bridges as road (...)

140A study in 2008–2009 of a forested and urban area in Porto Alegre, Brazil83 found that rope canopy bridges over roads were used by three mammal species. Rope canopy bridges were used by brown howler monkeys Alouatta guariba clamitans (4 of 6 bridges), porcupines Sphiggurus villosus (2 of 6 bridges) and white-eared opossums Didelphis albiventris (1 of 6 bridges). Six canopy bridges were installed in 2001– 2006 at sites close to a protected reserve where brown howler monkeys had been killed on roads or used power lines to cross them. Each bridge consisted of a horizontal ‘ladder’ made from rope and rubber hose (4 x 12 m parallel ropes with rubber hose ‘steps’ at 80 cm intervals and interlaced ropes forming a ‘X’ between each step). Camera traps and trained local observers monitored each of the six bridges for a total of 33–152 days during 6–15 months in 2008–2009.

  • 84 Soanes K., Vesk P.A. & van der Ree R. (2015) Monitoring the use of road-crossing structures by arbo (...)

141A replicated study in 2012–2014 at five sites along a highway through eucalyptus forest in Victoria, Australia84 found that canopy rope bridges were used by four species of arboreal marsupial to cross the road. Remote cameras detected 455 crossings of canopy bridges by squirrel gliders Petaurus norfolcensis, 229 by common brushtail possums Trichosurus vulpecula, 386 by common ringtail possums Pseudocheirus peregrinus and two by brush-tailed phascogales Phascogale tapoatafa. The study was conducted along two sections of the Hume Freeway, located 200 km apart. In 2007–2009, four 60–85-m-long canopy bridges, made of 15-mm-diameter rope woven into a flat net, 50 cm wide, were erected. They were 6 m above the road. A fifth bridge, 170 m long, was erected at ≥4 m high. Wildlife crossings were monitored between June 2012 and February 2013, using motion-triggered cameras.

  • 85 Goldingay R.L. & Taylor B.D. (2017) Targeted field testing of wildlife road-crossing structures: ko (...)

142A study in 2012–2016 in a forest site within a university campus in New South Wales, Australia85 found that northern mountain brushtail possums Trichosurus caninus and common ringtail possums Pseudocheirus peregrinus used canopy bridges but koalas Phascolarctos cinereus and squirrel gliders Petaurus norfolcensis did not. Twenty-two passes of northern mountain brushtail possums and two of common ringtail possums were detected on rope bridges. Koalas were detected 75 times and squirrel gliders three times in two nearby trees but were not detected on rope bridges. The trial was conducted in a 30 × 100 m eucalyptus-dominated forest patch. Rope-bridges of four designs extended 8–11 m between different pairs of trees. One rope bridge had 8-cm gaps between rope strands, one was made of woven-mesh with 1-cm gaps between strands, one was a ladder wrapped around internal wires to produce a sausage shape and one consisted of a woven mesh bridge with rope-ladder sides. One or two camera traps were used to monitor each rope-bridge and single cameras were used on two nearby reference trees, for 2.8–3.1 years/tree, between December 2012 and February 2016.

  • 86 Gregory T., Carrasco-Rueda F., Alonso A., Kolowski J. & Deichmann J.L. (2017) Natural canopy bridge (...)

143A study in 2012–2013 at a forest site in the Lower Urubamba region, Peru86 found that canopy bridges over a pipeline route were used by 25 arboreal mammal species with use increasing over 10 months, and crossing rates were higher over the bridges than at ground level. Twenty-five arboreal mammal species were recorded crossing over 13 canopy bridges (see original paper for details). Overall, use of the bridges increased over 10 months (total 40–55 crossings/100 nights). Crossing rates were higher over the bridges (total 45 crossings/100 nights) than below them at ground level (total 0.3 crossings/100 nights), although the difference was not tested for statistical significance. A gas pipeline route (10–25 m wide) was cleared through an area of native forest in June–August 2012. Thirteen canopy bridges (with branches from one or more trees connecting across the clearing) were preserved along a 5.2 km stretch of the route. Ten bridges remained functional by the end of the study in August 2013. Three failed due to exposure/tree damage. From September 2012, camera traps recorded crossing activity over the bridges (1–4 cameras/bridge) and at ground level below (2–3 cameras/ bridge) for 11–12 months.

  • 87 Soanes K., Mitchell B. & van der Ree R. (2017) Quantifying predation attempts on arboreal marsupial (...)

144A study in 2007–2015 at five points where a highway bisected woodland in Victoria, Australia87 found that arboreal marsupials using rope bridges did not suffer high predation rates when doing so. Among 13,488 detections of arboreal marsupials (from rope bridges and glider pole crossings combined — separate figures not given in paper), there was one recorded predation attempt. This was an unsuccessful night-time predation attempt on a squirrel glider Petaurus norfolcensis using a rope bridge, by an unidentified bird. In July 2007, five crossing structures were installed along 70 km of highway. Two were rope mesh canopy bridges (70 m long, 5 m wide) and three were poles for gliders (one or two poles/crossing, 12–14 m tall). Crossings were monitored with motion and heat activated cameras, from July 2007 to February 2015. Cameras recorded 5–10 images, 3 s apart (2007–2011) or a 10–20 s video (2011–2015). Predation attempts were detectable when animals were ≤5 m from each end of a canopy bridge, and ≤1 m from the top of each glider pole.

5.10. Install one-way gates or other structures to allow wildlife to leave roadways

145https://www.conservationevidence.com/​actions/​2558

146Seven studies evaluated the effects on mammals of installing one-way gates or other structures to allow wildlife to leave roadways. All seven studies were in the USA1–7.

147COMMUNITY RESPONSE (5 STUDIES)

148Survival (5 studies): Two before-and-after studies (one replicated), in the USA2,3, found that barrier fencing with one-way gates reduced deer-vehicle collisions. One of two studies (one before-and-after and one replicated, controlled), in the USA4,7, found that barrier fencing with escape gates along roads with one or more underpasses reduced moose-vehicle collisions4, whilst the other found no reduction in total mammal road casualty rates7. A replicated, controlled, before-and-after study in USA6 found that earth escape ramps reduced mammal road mortalities.

149POPULATION RESPONSE (0 STUDIES)

150BEHAVIOUR (4 STUDIES)

151Use (4 studies): One of two studies (one replicated) in the USA1,5 found that one-way gates allowed mule deer to escape when trapped along highways with barrier fencing1, whilst the other found that a small proportion used one-way gates5. A replicated, controlled, before-and-after study in the USA6 found that earth escape ramps were used more often than were one-way escape gates to enable deer to escape highways with barrier fencing. A replicated, controlled study in the USA7 found that barrier fencing with escape gates and underpasses facilitated road crossings by a range of mammals.

Background
Fencing alongside roads can prevent or reduce mammal access to roads and, thus, reduce vehicle collisions with mammals. However, mammals that do manage to access roads, either around fence ends or through defective sections of fence, can then become trapped on the road. One-way gates are intended to allow escape of such mammals from the road whilst not enabling additional animals to access the road. Other structures can serve a similar purpose, such as ramps up to fence-top height at one side.
See also:
Install barrier fencing along roads.

  • 88 Reed D.F., Pojar T.M. & Woodard T.N. (1974) Use of one-way gates by mule deer. The Journal of Wildl (...)

152A replicated study in 1970–1972 in Colorado, USA88 found that one-way gates allowed mule deer Odocoileus hemionus hemionus to escape when trapped along highways with barrier fencing. A total of 558 passages were recorded through eight gates, with 96 % in the one-way direction designed. Use of each gate ranged from seven to 335 passages. Track counts indicated that the gates enabled approximately 223 deer to escape the highway. There were also 3,293 tracks counted of deer approaching gates heading towards the highway but not passing through. During 31 trails, three types of one-way gate were tested (two at a time) along a fence between a field with a mule deer and one with its food. The location and direction of each gate was changed frequently. Eight gates, of the most effective design, were installed in 2.4-m-high barrier fencing along a 1.5-mile section of highway. Passages were monitored using track counts and mechanical counters. Gates along the highway were checked daily during migrations in 1970–1972.

  • 89 Reed D.F., Beck T.D.I. & Woodward T.N. (1982) Methods of reducing deer– vehicle accidents: benefit– (...)

153A before-and-after study in the 1970s along two highways in California, USA89 found that barrier fencing incorporating one-way gates reduced deer-vehicle collisions by 68–87 %. Fewer deer Odocoileus spp. road mortalities were recorded after construction of the six fence sections (average 2/km/year) than before (average 11/km/year). Six different lengths (1.9–7.7 km) of 2.4-m fencing were installed along Interstate 70 and Colorado Highway 82. Five of the fences were only on one side of the road, the other was on both sides and connected to an underpass. Four of the fences had one-way gates to allow deer to escape from the highway. Deer carcasses found along the road were counted in each fenced area before and after installation. Cost-benefit analysis was also undertaken using pre-fence mortality (dead deer) and fence effectiveness and estimates of cost of vehicle repair, deer value, discount rate, cost of fence and cost of fence maintenance (see original article for results).

  • 90 Ludwig J. & Bremicker T. (1983) Evaluation of 2.4 m fences and one-way gates for reducing deer vehi (...)

154A replicated, before-and-after study in 1977–1979 along two highways in Minnesota, USA90 found that barrier fencing with one-way gates decreased deer-vehicle collisions. Along two fenced road sections, 1.3 and 8 deer/year were killed compared to an estimated 20/year in the pre-fence period. One fence was installed in a ditch with 1 m of water, meaning 30 % of gates could not be used to escape the highway. Overall, 69 % of 51 passages through gates were in the correct direction, i.e. from the highway to outside the fenced corridor. Two sections of 2.4-m-high fence with one-way gates along new highways were monitored for 18 months. Fences were 4 and 5 km long with nine and 10 pairs of gates (30 m apart), respectively. Deer were monitored crossing through gates by using baler counters and track beds. Deer-vehicle collisions were monitored for one year before (along old adjacent highway) and 18 months after installation. Cost-benefit analysis was also carried out (see the original article for further details).

  • 91 McDonald M.G. (1991) Moose movement and mortality associated with the Glenn Highway expansion. Alce (...)

155A before-and-after study in 1977–1990 in Alaska, USA91 found that barrier fencing with one-way gates, along with an underpass and road lighting, reduced vehicle collisions with moose Alces alces. Effects of fencing, gates, lighting and the underpass could not be separated. There were fewer moose-vehicle collisions after installation of fencing with one-way gates, an underpass and lighting (0.7/year) than before (17/year). There was no significant difference in the distribution of moose in relation to the highway between after and before fence installation. A total of 17 moose were observed using one-way gates and tracks suggested gates were used frequently. However, this meant that moose were regularly getting onto the highway. The first gates installed stayed open if swung all the way open and gates got stuck open below 0°C, because of the lubricant used. In October 1987, road lighting was installed along 11.5 km of the highway. Fencing and 30 one-way gates were installed along 5.5 km of this section and an underpass was created. Moose-vehicle collisions were monitored before (1977–1987) and after (1987–1990) installation. One-way gates were monitored using track counts in snow.

  • 92 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing dee (...)

156A study in 1994–1995 along two highways through grassland and shrubland in Utah, USA92 found that one-way gates were used by some mule deer Odocoileus hemionus to escape a highway, but most did not cross through them. From 243 instances in which deer approached gates from the highway, 40 deer (16 %) used gates to leave the highway. None of 128 deer that approached from the side away from the highway passed through gates. In September 1994, five and four crossing points were installed along a two-and a four-lane highway respectively. Fencing, 2.3 m high, directed deer to crossing points. Warning signs alerted approaching motorists to crossing points. Four one-way gates were installed at each crossing to allow deer trapped along the road to escape. One-way gate specifications were not detailed in the paper. Earthen track beds at 12 randomly selected one-way gates were checked at least once each week from September 1994 to November 1995 (except January–March 1995).

  • 93 Bissonette J. & Hammer M. (2000) Comparing the effectiveness of earthen escape ramps with one-way g (...)

157A replicated, controlled, before-and-after study in 1997–1999 along two highways in Utah, USA93 found that earth escape ramps reduced road mortalities and were used more often than one-way escape gates to enable deer to escape highways with 2.4-m-high barrier fencing. Road mortalities decreased more after ramp installations at two sites (after: 4.8 and 2.0 killed/km; before: 6.7 and 4.6 killed/km) than at a control site during this time (after: 4.0 killed/km; before: 5.2 killed/ km). At one site, 188 successful ramp crossings were recorded. At the other, 192 were recorded. Combined values from both sites showed ramps were used 8–11 times more often than were one-way gates. Nine earth ramps (1.5-m drop-off) were installed along 2.4 km of highway in 1997 and seven along 2.4 km of another highway in 1998. Ten and eight one-way gates respectively were installed previously at these sites (installation date not stated). Animal movements across ramps and through gates were monitored from May–July until October in 1998 and 1999 using track plots. Road mortality and monthly spotlight counts of deer were carried out before and after construction of ramps along both sections, and along an 8-km control section (1-m fencing, no mitigation measures) in 1997–1999. Cost-benefit analysis was also carried out (see original article for results).

  • 94 McCollister M.F. & van Manen F.T. (2010) Effectiveness of wildlife underpasses and fencing to reduc (...)

158A replicated, controlled study in 2000–2007 along a highway in North Carolina, USA94 found that barrier fencing with escape gates and underpasses facilitated road crossings by a range of mammals but did not reduce road casualties. A similar rate of mammal road casualties was recorded over one year on road sections with fencing, escape gates and underpasses (5.0/km) as on sections without (5.1/km). A four-lane highway was constructed with three underpasses. Barrier fencing, 3 m high, was installed ≥800 m along the highway from each underpass. Gates allowed trapped animals to escape the highway. Road deaths were recorded along 6 km of road with fencing and underpasses and 11 km without, twice/week, from July 2006–July 2007.

5.11. Install barrier fencing along roads

159https://www.conservationevidence.com/​actions/​2567

160Twelve studies evaluated the effects on mammals of installing barrier fencing along roads. Eight studies were in the USA1– 6,9,10, one each was in Canada7, Germany8 and Brazil11 and one spanned the USA, Canada and Sweden12.

161COMMUNITY RESPONSE (0 STUDIES)

162POPULATION RESPONSE (9 STUDIES)

163Survival (9 studies): Three controlled studies, in the USA6, Germany8 and Brazil11, found that roadside fencing or equivalent barrier systems reduced the numbers of mammals, including wildcats8 and coypu11, killed by vehicles on roads. Two before-and-after studies, in the USA2,3, found that roadside fencing with one-way gates to allow escape from the road, reduced the number of collisions between vehicles and deer. A study in the USA4 found that a 2.7-m-high fence did not reduce road-kills of white-tailed deer compared to a 2.2-m-high fence. A controlled, before-and-after study in the USA5 found that barrier fencing with designated crossing points did not significantly reduce road deaths of mule deer. A replicated, controlled, before-and-after study in Canada7 found that electric fences, (along with an underpass beneath one highway), reduced moose-vehicle collisions. A review of fencing studies from USA, Canada and Sweden12, found that longer fencing along roadsides led to a greater reduction of collisions between large mammals and cars than did shorter fence sections.

164BEHAVIOUR (5 STUDIES)

165Behaviour change (5 studies): A controlled, before-and-after study in the USA1 found that 2.3-m-high fencing in good condition prevented most white-tailed deer accessing a highway. A replicated, controlled, before-and-after study in Canada7 found that electric fences reduced moose access to highways. Three studies (two replicated), in the USA4,9,10, found that higher fences (2.4–2.7 m) prevented more white-tailed deer from entering highways than did fences that were 2.2 m high4, 1.2 m high with outriggers9 or 1.2–1.8 m high10.

Background
Wildlife barrier fencing aims to prevent animals from crossing roads. They are typically wire mesh fences 2–2.5 m high running parallel to the road. Although fencing may protect wildlife from traffic, it should not create an absolute barrier that prevents migration, isolates populations, fragments habitat, or causes injuries. Wildlife fencing is therefore usually combined with safe crossing opportunities such as wildlife underpasses and overpasses (see
Install overpasses over roads/railways, Install tunnels/culverts/underpass under railways, Install tunnels/culverts/underpass under roads). Wildlife escapes, such as one-way gates, are often integrated with wildlife fencing to allow animals that do manage to cross the fence to escape from the fenced road (see: Install one-way gates or other structures to allow wildlife to leave roadways). Wildlife such as deer frequently try to pass through holes in fences and so fences must be well maintained (Ward 1982). Studies included here are those that specifically assess fence effectiveness, sometimes in combination with other collision reduction actions, but not where effects of fencing cannot be separated from effects of road underpasses. For these interventions combined, see Install barrier fencing and underpasses along roads.
As well as the threat to wildlife from vehicles, fencing is often placed to reduce dangers and costs to motorists that can result from collisions with wildlife. Assessment of whether or not to install fences may be based on a cost-benefit analysis (e.g. Huijser 2009).

166Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyoming. Transportation Research Record, 859, 8–13.

167Huijser M.P., Duffield J.W., Clevenger A.P., Ament R.J. & McGowan P.T. (2009) Cost–benefit analyses of mitigation measures aimed at reducing collisions with large ungulates in the United States and Canada: a decision support tool. Ecology and Society, 14, article 15.

  • 95 Falk N.W., Graves H.B. & Bellis E.D. (1978) Highway right-of-way fences as deer deterrents. The Jou (...)
  • 96 Reed D.F., Beck T.D.I. & Woodward T.N. (1982) Methods of reducing deer– vehicle accidents: benefit– (...)

168A controlled, before-and-after study in 1975 along a highway through mixed hardwood forest in Pennsylvania, USA95 96found that, provided it was in good repair, 2.3-m-high fencing prevented most white-tailed deer Odocoileus virginianus from crossing a highway. Significantly fewer deer crossed the fence once it had been repaired (0–6), compared to before (77–84) and once repairs were undone (23–153), and compared to control sections (on which repairs were not carried out) during the same periods (24–247; 111–141; 53–268 crossings respectively). The 2.3-m-high fences ran either side of a four-lane highway, with a top section angled 45° away from the highway. The study site comprised two 0.8-km control sections with a 1.6-km experimental section between. Fence defects included gaps under the fence and lowered or broken top wires. Tracks in snow and sand along the fence both sides of the highway were monitored before repairs, after repairs along the experimental section and after repairs were undone. This cycle was implemented once in both winter and spring 1975 and tracks were surveyed over five days during each period.

169A before-and-after study in the 1970s along two highways in California, USA found that barrier fences, including one connected to an underpass, and others to one-way gates, reduced deer-vehicle collisions by 68–87 %. Fewer deer Odocoileus spp. road mortalities were recorded after construction of the six fence sections (average 2/km/year) than before (average 11/km/year). Six different lengths (1.9–7.7 km) of 2.4-m fencing were installed along Interstate 70 and Colorado Highway 82. Five of the fences were only on one side of the road, the other was on both sides and connected to an underpass. Four of the fences had one-way gates to allow deer to escape from the highway. Deer carcasses found along the road were counted in each fenced area before and after installation. Cost-benefit analysis was also undertaken using pre-fence mortality (dead deer) and fence effectiveness and estimates of cost of vehicle repair, value of deer, discount rate, cost of fence and cost of fence maintenance (see the original article for results).

  • 97 Ludwig J. & Bremicker T. (1983) Evaluation of 2.4 m fences and one-way gates for reducing deer vehi (...)

170A replicated, before-and-after study in 1977–1979 along two highways in Minnesota, USA97 found that barrier fencing with one-way gates decreased deer-vehicle collisions. Along two fenced road sections, 1.3 and 8 deer/year were killed compared to an estimated 20/year in the pre-fence period. One fence was installed in a ditch with 1 m of water, meaning 30 % of gates could not be used to escape the highway. Overall, 69 % of 51 passages through gates were in the correct direction, i.e. from the highway to outside the fenced corridor. Two sections of 2.4-m-high fence with one-way gates along new highways were monitored for 18 months. Fences were 4 and 5 km long with nine and 10 pairs of gates (30 m apart), respectively. Deer were monitored crossing through gates by using baler counters and track beds. Deer-vehicle collisions were monitored for one year before (along old adjacent highway) and 18 months after installation. Cost-benefit analysis was also carried out (see the original article for further details).

  • 98 Feldhamer G.A., Gates J.E., Harman D.M., Loranger A.J. & Dixon K.R. (1986) Effects of Interstate hi (...)

171A study in 1981–1983 in forest in Pennsylvania, USA98 found that a 2.7-m-high deer-proof fence reduced the number of white-tailed deer Odocoileus virginianus on the highway compared to a 2.2-m-high fence, but did not reduce road-kills. A total of 240 groups of deer were observed on the highway alongside 23 km of 2.7-m-high fence compared to 465 alongside 18 km of 2.2-m-high fence. Overall, 1,687 deer (82 % of all sightings) were on highway verges. In 1981–1983, one hundred deer died on the highway (1.2 deer/km/year) and numbers did not differ between fence types. Deer were monitored along a 41-km section of a 4–6-lane highway, 23 km of which had a 2.7-m-high mesh fence and the remainder a 2.2-m-high fence with an overhang. Thirty-six spotlight surveys were undertaken along the highway from January 1981 to January 1983.

  • 99 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing dee (...)

172A controlled, before-and-after study in 1991–1995 along two highways in Utah, USA99 found that barrier fencing with designated crossing points and warning signs did not reduce road deaths of mule deer Odocoileus hemionus. Deaths fell on both fenced and unfenced sections but the rate of fall was not significantly higher on fenced road sections (after: 36–46; before: 111–148) than on unfenced sections (after: 34–63; before: 75–123). The number of deer on road verges fell by 34–55 % following fence installation. In September 1994, four and five crossing points were installed along a two-and a four-lane highway respectively. Fencing, 2.3 m high, restricted access to roadsides and directed deer towards crossing points. At these points, deer could jump a 1-m-high fence into funnel shaped fencing (2.3 m high) with a narrow opening to the road. One-way gates allowed deer trapped along the road to escape. Three warning signs, spaced 152 m apart, and painted lines across the road at crossings, indicated to drivers that it was a crossing point. Road deaths (weekly) and behaviour were monitored along fenced and nearby unfenced roads before and after installation, from October 1991 to November 1995. Spotlight count surveys were undertaken twice/ month.

  • 100 Dodd C.K., Barichivich W.J. & Smith L.L. (2004) Effectiveness of a barrier wall and culverts in red (...)

173A controlled, before-and-after study in 1998–2002 along a highway in Florida, USA100 found that a barrier wall-culvert system reduced mammal road-kills. After construction, 33 mammals of ≥12 species were recorded dead on the 2.8-km section of road with the barrier (2.8 km) compared to 50 mammals on a 400-m section without barriers. Of those killed along the barrier, 17 were rice rats Oryzomys palustris, which climbed adjacent vegetation to get over the barrier. In 2000–2001, a 1-m-high concrete wall with 15-cm overhanging lip was constructed along a 2.8-km section of a highway. Eight concrete culverts were spaced 200–500 m apart below the wall. Roadkills were monitored on three days/week before (August 1998–1999) and after (March 2001–March 2002) barrier wall construction.

  • 101 Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Electric fencing (...)

174A replicated, before-and-after study in 2003–2005 along two highways in Québec, Canada101 found that electric fences, along with an underpass beneath one highway, reduced moose Alces alces access to highways and moose-vehicle collisions. There were fewer moose-vehicle collisions after fence construction (zero) than before (1–5/year) and moose tracks on the road decreased by 76–84 %. Only 33 % (of 53) of moose tracks on the road were from moose that had crossed a fence; most entered through vehicle access routes (31 %) or at fence ends (7 %). Fences prevented 78 % (7/9) of radio-collared moose from crossing the highway. Electric fences (1.5 m high, cables 0.3 m apart) were installed along both sides of a 5-km section of Highway 175 in 2002 and a 10-km section of Highway 169 in 2004 (both two-lane). Moose were monitored along fenced and adjacent equal-length unfenced road sections using weekly track surveys in May–August of 2003–2005. GPS collars were fitted to 47 moose and locations recorded every 2–3 hours for 1–3 years. An underpass was constructed along one highway (23 m long, 16 m wide, 7 m high) and a fence opening on the other (that triggered dynamic warning road signs).

  • 102 Klar N., Herrmann M. & Kramer-Schadt S. (2009) Effects and mitigation of road impacts on individual (...)

175A controlled study in 2001–2005 along a motorway through forest and agricultural land in Germany102 found that installing roadside fencing designed to keep wildcats Felis silvestris off the road reduced road-related wildcat mortality. Wildcat mortality was lower where wildcat fencing was installed (0.07 deaths/km/year) than in areas with other types of fencing (0.41–0.44 deaths/km/year). This difference was not tested for statistical significance. In 2002, two-metre-high wildcat fencing, with 5 × 5 cm mesh, a 50-cm-wide metal sheet overhang and a board down to 30 cm below ground, was installed along 6.4 km of road. Fine-meshed fence (same specifications as the wildcat fence, but without the overhang) was installed along 4 km of road. Standard wildlife fencing was installed on 7 km of road. Wildcat mortality data collected by researchers was supplemented by reports from motorway authorities and members of the public.

  • 103 Gulsby W.D., Stull D.W., Gallagher G.R., Osborn D.A., Warren R.J., Miller K.V. & Tannenbaum L.V. (2 (...)

176A replicated, before-and-after study in 2009–2010 along a university campus road in Georgia, USA103 found that a 2.4-m-high fence was more successful at preventing white-tailed deer Odocoileus virginianus accessing the road than was a 1.2-m-high fence with outriggers attached to the top. Fewer deer crossed the road in a section with 2.4-m-high fencing (<0.01 crossings/day) than in a section with 1.2-m-fence with 0.6-m outriggers (0.05 crossings/day). Before fence construction, deer made 0.3–1.0 crossings/day. In May–June 2009, a vertical wire fence (1.6 km long, 2.4-m-high) and an outrigger fence (1.6 km long, 1.2 m high with a 0.6-m-long outrigger at 45°, attached to the top and threaded with five wires) were erected. Between January 2009 and March 2010, movements of eight adult female deer were monitored using GPS collars. Four deer had home ranges that overlapping the 2.4-m-high fence and four overlapped the 1.2-m-high fence with outriggers.

  • 104 Stull D.W., Gulsby W.D., Martin J.A., D’Angelo G.J., Gallagher G.R., Osborn D.A., Warren R.J. & Mil (...)

177A replicated, controlled study in 2008 in fields in Georgia, USA104 found that white-tailed deer Odocoileus virginianus did not jump 2.4-m-high barrier fencing, at 1.8 m fewer jumped if fencing was opaque and 1.2-m-high fences with outriggers angled towards deer were jumped less than those angled away. Among deer that jumped the 1.2-m control fence, fewer jumped each subsequently taller fence (1.5 m: 92 %; 1.8 m: 75 %; 2.1 m: 42 %; 2.4 m: 0 %). In opaque fence trails, 90 % jumped 1.2 and 1.5-m fences and 50 % jumped the 1.8-m fence. With an outrigger, fewer jumped when this was angled towards deer (60 %) than away (90 %). Three treatment areas (0.1–0.2 ha) were bisected with a test fence. Designs were woven-wire fencing either alone (1.5, 1.8, 2.1 and 2.4 m high), covered with opaque fabric (fence 1.2, 1.5 and 1.8 m high), 1.2 m high with a 0.6-m 50 % opaque plastic outrigger angled at 45°, or a 1.2-m-high control fence. Ten adult female deer were each tested with each design in each treatment area. After 48 hours of habituation and limited food, deer were enclosed on the opposite side of test fences from food. Deer were videoed throughout each 25-hour trial.

  • 105 Bager A. & Fontoura V. (2013) Evaluation of the effectiveness of a wildlife roadkill mitigation sys (...)

178A controlled, before-and-after study in 1995–2002 along a highway through a wetland in Rio Grande do Sul, Brazil105 found that roadside fencing and underpasses reduced the number of road-kills of coypu Myocastor coypus. Fewer coypu were killed by cars after fencing was installed (3.6 coypu/100 km/day) than before (8.3 coypu/100 km/day). The total number of animal road-kills (including all mammals, birds and reptiles) after fencing was installed (10.3 animals/100 km/day) was smaller than before fencing (15.3 animals/100 km/day) (this result was not tested for statistical significance). Road-kill rates fell in fenced sections but increased in the unfenced section (see paper for details). Two sections of a two-lane highway, totalling 10.2 km long, were fenced in 1998. The fence was 50–100-mm mesh, 1.10 m high. Between these sections was a 5.5-km-long unfenced section. Nineteen underpasses in total were also installed along these three road sections. Road-kills were counted from a car from July 1995 to June 2002. Monitoring was conducted at an average speed of 50 km/h, by 2–4 observers, along 15.7 km of highway. A total of 619 monitoring runs were made before fence installation (July 1995 to September 1998) and 571 afterwards (October 1998 to June 2002).

  • 106 Huijser M.P., Fairbank E.R., Camel-Means W., Graham J., Watson V., Basting P. & Becker D. (2016) Ef (...)

179A 2016 review of fencing studies from USA, Canada and Sweden106 found that longer fencing along roadsides led to a greater reduction of collisions between large mammals and cars than did shorter fence sections. Results were not tested for statistical significance. Fences reduced collisions between large mammals and cars more in road sections fenced along >5 km (average 84 % reduction in relation to before fencing) than in sections fenced along <5 km (average 53 % reduction). The review identified 21 fenced road sections (18 from the USA, two from Canada and one from Sweden). Fences were 0.6–33.8 km long and 2.1–2.5 m high. Large mammals targeted by surveys included white-tailed deer Odocoileus virginianus, moose Alces alces, roe deer Capreolus capreolus, mule deer Odocoileus hemionus, elk Cervus canadensis and bighorn sheep Ovis canadensis.

5.12. Install barrier fencing and underpasses along roads

180https://www.conservationevidence.com/​actions/​2571

181Fifty-five studies evaluated the effects on mammals of installing barrier fencing and underpasses along roads. Twenty-seven were in the USA1–8,15–19,21,25,30,35,39,41,43–45,47,51,52a, 52b, 53, nine were in Canada9–11,13,22,23,28,46,54, seven were in Australia14,20,29,36,48–50, two each were in Spain24,32, Portugal26,31, the UK27,42 and Sweden33,34, one each was in Denmark12, Germany37 and Croatia38 and one was a review covering Australia, Europe and North America40.

182COMMUNITY RESPONSE (0 STUDIES)

183POPULATION RESPONSE (15 STUDIES)

184Survival (15 studies): Eleven of 15 studies (including 12 before-and-after studies and two site comparisons), in the USA1,5,8,16,21,35,39,44,45, Australia29,36, Sweden33,34 and Canada13,28, found that installing underpasses and associated roadside barrier fencing reduced collisions between vehicles and mammals1,5,13,28,29,33–36,44,45. Three studies found that the roadkill rate was not reduced8,16,39 and one study found that vehicle-mammal collisions continued to occur after installation21.

185BEHAVIOUR (52 STUDIES)

186Use (52 studies): Seventeen of 18 studies (including 10 before-and-after studies) in the USA1–4,16–19,25,30,35,41,44,45,52b,53 Canada28 and Sweden33, which reported exclusively on ungulates, found that underpasses installed along with roadside barrier fencing were used by a range of ungulate species. These were mule deer1,2,3,17,19,45,53, mountain goat4, pronghorn18, white-tailed deer19,41,52b elk19,25, moose28 and Florida Key deer30,35,44. The other study found that underpasses were not used by moose33 whilst one of the studies that did report use by ungulates further reported that they were not used by white-tailed deer16. Further observations from these studies included that elk preferred more open, shorter underpasses to those that were enclosed or longer25, underpass use was not affected by traffic levels41 and that mule deer used underpasses less than they used overpasses53. Thirty-four studies (including four before-and-after studies, seven replicated studies, three site comparisons and two reviews), in the USA6–8,15,21,39,43,47,51,52a, Canada9–11,22,23,46,54, Australia14,20,29,36,48,49,50, Spain24,32, Portugal26,31, the UK27,42, Denmark12, Germany37, Croatia38 and across multiple continents40, that either studied mammals other than ungulates or multiple species including ungulates, found that underpasses in areas with roadside fencing were used by mammals. Among these studies, one found that small culverts were used by mice and voles more than were larger underpasses22, one found that bandicoots used underpasses less after they were lengthened49 and one found that culverts were used by grizzly bears less often than were overpasses54.

Background
Schemes designed to reduce collisions between vehicles and wild mammals may use multiple interventions. Two of the most common ones, installing barrier fencing and providing routes for mammals to travel underneath roads, are often employed within the same scheme. This may entail regular roadside fencing with entrances to underpasses set further back away from the road or fencing may be designed to adjoin the sides of underpass entrances. Sometimes, fencing may be installed to form a funnel leading towards underpass entrances.
This intervention includes studies where these two actions are in place at the same site. In most studies, all underpasses (where there are multiple crossings) are beneath stretches or roads that have barrier fencing. In a minority, just some of the underpasses monitored are along stretches with barrier fencing. Studies included use of either conventional fencing, electric fences or other barriers, such as walls. Most studies report solely on the use of crossings or trends in numbers of mammals killed on roads. There is an absence of studies reporting on wider population-level effects of the presence of these structures.
See
Install tunnels/culverts/underpass under roads for studies where underpasses are either installed without use of barrier fencing or where it is not clear from the study that barrier fencing was installed. See also Install barrier fencing along roads for studies which, in some cases, included underpasses but where the specific effect of fencing was evaluated.

187A before-and-after study in 1970–1973 along a highway in Colorado, USA (1; same experimental set-up as 2) found that an underpass, in areas with roadside fencing and one-way gates, reduced road mortalities and allowed most local mule deer Odocoileus hemionus to migrate safely under a highway. There were 14 deer-vehicle accidents/year within the fenced section compared to 36/year before installation of the underpass and fencing. On average, 345 mule deer (61 % of the local population) used the culvert each season, with up to 17 crossings/day. Underpass use was not affected by artificial lighting. On average, 17 % of deer used one-way gates to escape the highway and 17 % went round the ends of fences or did not cross. In 1970, a concrete box underpass (3 × 3 × 30 m, with two skylights) was installed under a 3.2-km section of highway. The 2.4-m-high barrier fencing either side had eight one-way gates. Underpass-use was monitored by track counts and mechanical counters daily and a video camera at night during spring–summer and autumn migrations in 1970–1973. Artificial lighting was alternately turned on and off over 28 nights, in June and October 1973. Tracks at gates and deer movements along the fence were monitored each morning.

188A study in 1974–1979 along a highway in Colorado, USA (2; same experimental set-up as 1) found that an underpass, in an area with roadside fencing, continued to be used by mule deer Odocoileus hemionus 4–9 years after installation Between 1.3 and 5.8 deer/morning (average 2.3) were observed exiting the underpass each year (total 298 deer). Deer behaviour suggested that 75 % of animals exiting the underpass were reluctant, wary, or frightened. Eleven hesitated just inside the exit and 23 showed wariness or excitability after exiting the underpass. Behavioural responses of deer to the underpass were reported not to have changed substantially over 10 years (1970–1979) of spring-summer use. In 1970, a concrete box underpass (3 m high, 3 m wide, 30 m long) was installed under a 3.2-km section of highway. Entrances were separated from the road by 2.4-m-high barrier fencing. Deer were observed from 130 m away, at 05: 00–07: 00 h, on 9–30 days (average 16), during each spring/ summer migration in 1974–1979. Behavioural responses were likened (but not compared numerically) with those from earlier monitoring that commenced in 1970.

  • 107 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass (...)
  • 108 Reed D.F. (1981) Mule deer behavior at a highway underpass exit. The Journal of Wildlife Management(...)
  • 109 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyom (...)

189A study in 1977–1979 along a highway through shrubland in Wyoming, USA107 108109found that underpasses, in areas with roadside fencing, were used by mule deer Odocoileus hemionus to cross under the road. During four migration periods (two spring, two autumn–winter) immediately after underpasses were connected to a fence, >4,000 crossings through underpasses were made by deer (precise figure not stated). The study was conducted along a 7.8-mile stretch of highway constructed in late 1970. The highway was located on a migration route of 1,600–2,000 mule deer. Over four migratory periods, seven underpasses (length: 110–393 feet; width: 10–50 feet; height: 10–17 feet) were monitored for deer use. Underpasses were connected to 8-foot-high roadside fencing that guided animals towards entrances. From 1978, an attempt was made to attract deer to six of the seven underpasses by baiting with alfalfa hay, supplemented with apple pulp or by vegetable trimmings. Deer movements were monitored by track counts and surveillance cameras.

  • 110 Singer F.J. & Doherty J.L. (1985) Managing mountain goats at a highway crossing. Wildlife Society B (...)

190A before-and-after study in 1975–1981 in Montana, USA110 found that two underpasses and roadside fencing increased highway crossing success by mountain goats Oreamnos americanus. After construction, 90 % of highway crossing attempts were successful compared to 86 % during and 74 % before construction (unsuccessful attempts were when the crossing was temporarily thwarted). Crossing hesitations and run-backs decreased by 80 % after underpass construction, delay time before crossing declined by about 30 % and signs of fear (measured by an index) decreased. All crossings were successful when there was no disturbance, but success decreased to 85 % when humans or traffic were present. A large underpass (3–8 m high, 23 m wide, 11 m long) was constructed where goats were observed crossing. In addition, a new road bridge included a ledge underneath for goats to cross (3 m high, 3 m wide, 11 m long). A sheer wall downhill and barrier fencing prevented goats crossing between underpasses. Old goat trails were removed and new trails to underpasses dug. Goat crossings were monitored before (1975), during (May–October 1980) and after underpass construction (October 1980–September 1981).

  • 111 McDonald M.G. (1991) Moose movement and mortality associated with the Glenn Highway expansion. Alce (...)

191A before-and-after study in 1977–1990 along a highway in Alaska, USA111 found that barrier fencing with one-way gates, along with an underpass and road lighting, reduced vehicle collisions with moose Alces alces. Effects of fencing and the underpass could not be separated from those of gates and lighting. There were fewer moose-vehicle collisions after installation of fencing with one-way gates, an underpass and lighting (0.7/year) than before (17/year). There was no significant difference in the distribution of moose in relation to the highway after and before fence installation. A total of 17 moose were observed using one-way gates and tracks suggested gates were used frequently. However, this meant that moose were regularly getting onto the highway. The first gates installed stayed open if swung all the way open and gates got stuck open below 0°C, because of the lubricant used. In October 1987, road lighting was installed along 11.5 km of the highway. Fencing and 30 one-way gates were installed along 5.5 km of this section and an underpass was created. Moose-vehicle collisions were monitored before (1977–1987) and after (1987–1990) installation. One-way gates were monitored using track counts in snow.

  • 112 Foster M.L. & Humphrey S.R. (1995) Use of highway underpasses by Florida panthers and other wildlif (...)

192A study in 1994–1995 in Florida, USA112 found that four underpasses beneath a highway, in areas with roadside fencing, were used by Florida panthers Felis concolor coryi and a range of other mammal species. Ten crossings were recorded through underpasses by panthers, as were 361 by white-tailed deer Odocoileus virginianus, 133 by bobcats Lynx rufus, 167 by raccoons Procyon lotor and two by black bears Ursus americanus. Panther records were thought to relate to two individuals. Four concrete bridge underpasses (21–26 m wide, 49 m long) were monitored along a 64-km stretch of a four-lane, divided highway. Barrier fencing, 3 m high, ran along the highway. Infrared game counters and cameras were used to monitor underpasses for 2, 10, 14 and 16 months in 1994–1995.

  • 113 Land D. & Lotz M. (1996) Wildlife crossing designs and use by Florida panthers and other wildlife i (...)

193A replicated study in 1995 along two highways in Florida, USA113 found that large underpasses and box culverts, in areas with roadside fencing, were used by a range of mammal species. Mammals recorded using large underpasses were white-tailed deer Odocoileus virginianus (5.1 crossings/month), panther Felis concolor (2.2), bobcat Lynx rufus (1.3) and raccoon Procyon lotor (1.4). Box culverts were additionally used by red foxes Vulpes vulpes and otters Lontra canadensis. Two box culverts (2.4 m high, 7 m wide, 15 m long) were monitored along a 6.4-km section of a highway. Two of nine large underpasses (21–25 m wide, 49 m long) with vegetation were monitored along a 15-km section of a different highway. Highways had barrier fencing 3.4 m high with a 1-m overhang. Underpasses were monitored from March or April 1995 (end date not stated) using an infra-red digital counter and camera and by counting tracks.

  • 114 Roof J. & Wooding J. (1996) Evaluation of the S.R. 46 wildlife crossing in Lake County, Florida. Fl (...)
  • 115 Hayes I. & Goldingay R.L. (2009) Use of fauna road-crossing structures in north-eastern New South W (...)
  • 116 Hayes I. & Goldingay R.L. (2009) Use of fauna road-crossing structures in north-eastern New South W (...)
  • 117 Bond A.R. & Jones N.J. (2008) Temporal trends in use of fauna-friendly underpasses and overpasses. (...)
  • 118 Baker A., Knowles M. & Latham D. (2007) Using clay drain seals to assess the use of dry culverts in (...)

194A before-and-after study in 1993–1995 of a highway in Florida, USA114 found that an underpass beneath a highway, in an area with roadside fencing, was used by mammals but the road-kill rate was not reduced. Nine mammal species used the crossing. Most crossings were by rabbits Sylvilagus palustris (69 crossings), racoons Procyon lotor (61), armadillos Dasypus novemcinctus 115, opossums Didelphis virginiana 116, foxes Vulpes vulpes 117and bobcats Lynx rufus 118. The number of mammals of squirrel size or larger killed on the fenced road section was not significantly different in the 11 months after fence installation (13 animals) relative to the 11 months before (10 animals). A wildlife crossing (14.3 m long, 7.3 m wide and 2.4 m tall) was constructed under the two-lane highway between summer and December 1994. A 3-m-high fence extended along both sides of the highway, 0.6 km in one direction and 1.1 km in the other. Underpass use was determined in December 1994 to December 1995 by footprint surveys and by using a motion-triggered camera. Road-kills were surveyed three times/week from November 1993 to December 1995.

  • 119 Clevenger A.P. (1998) Permeability of the Trans-Canada highway to wildlife in Banff National Park: (...)

195A study in 1996–1997 along a highway through forest and grassland in Alberta, Canada119 found that underpasses, in areas with roadside fencing, were used by at least 10 species of medium-and large-sized mammals. Over 12 months at 11 underpasses, there were 1,338 detections of elk Cervus canadensis, 538 of deer Odocoileus spp., 373 of coyotes Canis latrans, 97 of black bears Ursus americanus, 77 of wolves Canis lupus, 29 of cougars Puma concolor and six of grizzly bears Ursus arctos. Most visits resulted in completed passages (96–100 %, depending on species). Bighorn sheep Ovis canadensis, mountain goats Oreamnos americanus and moose Alces alces were also detected (frequency not reported). Elk, deer and coyotes used all 11 underpasses, black bears used nine, wolves used six, cougars used five and grizzly bears used three underpasses. The study was conducted along 27 km of a four-lane highway. Wildlife movements were monitored through seven cement open-span underpasses, under two bridges over creeks and through two metal culverts. Barrier fencing, 2.4 m high, ran alongside the highway. Underpasses, constructed in 1986–1991, were located in twinned highway sections. Animal tracks were monitored at each end of each crossing within a sand, silt and clay mix (2 × 4 m) every 3–4 days from November 1996 to October 1997.

  • 120 Clevenger A.P. & Waltho N. (1999) Dry drainage culvert use and design considerations for small-and (...)

196A study in 1999 along a highway in Alberta, Canada120 found that drainage culverts, in areas with roadside wildlife exclusion fencing, were used by small-and medium-sized mammals. Crossings at 24 culverts included snowshoe hare Lepus americanus (13 crossings at 8 culverts), red squirrel Tamiasciurus hudsonicus (6 crossings at 4 culverts), deer mouse Peromyscus maniculatus (161 crossings at 14 culverts), voles Arvicolinae spp. (5 crossings at 3 culverts) and shrews Sorex spp. (43 crossings at 16 culverts). Weasels Mustela sp., and martens Martes americana also used culverts. Culvert use positively correlated with traffic volume and road width (hare, squirrel, vole), road clearance (squirrel) and culvert length (hare, vole) and negatively correlated with distance to cover (vole), age (hare, squirrel) and openness (squirrel, vole). Shrews preferred larger, more open culverts. Vegetation cover effected use by hares, squirrels and voles. The Trans-Canada highway was expanded to four lanes, with 2.4-m-high wildlife exclusion fencing, in three sections, completed in 1986, 1988 and 1997. Twenty-four drainage culverts were monitored along a 55-km highway section, using multiple sooted track-plates (75 × 30 cm) in each culvert. Plates were checked weekly in January–March 1999. Structural and landscape variables were recorded at culverts.

  • 121 Clevenger A.P. & Waltho N. (2000) Factors influencing the effectiveness of wildlife underpasses in (...)

197A study in 1995–1998 along a highway in Alberta, Canada121 found that underpasses, in areas with roadside barrier fencing, were used by large herbivores and carnivores. A total of 8,959 elk Cervus canadensis appearances, 2,411 deer Odocoileus sp. appearances and two moose Alces alces appearances were recorded at 11 underpasses. There were also 193 appearances of black bears Ursus americanus, seven of grizzly bears Ursus arctos, 117 of cougars Puma concolor and 311 of wolves Canis lupus. On 98 % of visits, the animal passed through. Features that positively influenced use of underpasses included increased length, noise level and distance to drainage. Increased width, openness, distance to forest and human activities negatively influenced their use. Nine cement open-span underpasses and two metal culverts (length: 26–96 m, width: 4–15 m, height: 2.5–4.0 m) were monitored along a 27-km stretch of the four-lane Trans-Canada Highway. Barrier fencing, 2.4 m high, ran alongside the highway. Tracks were monitored in sand or clay at each end of each crossing, every 3–4 days, from January 1995 to March 1996 and November 1996 to June 1998. Information about structure, landscape and human activity were recorded for each underpass.

  • 122 Mathiasen R. & Madsen A.B. (2000) Infrared video-monitoring of mammals at a fauna underpass. Intern (...)

198A study in 1997 along a highway in Jutland, Denmark122 found that an underpass, in an area with roadside barrier fencing, was used by four mammal species. These were red fox Vulpes vulpes (122 observations, 161 tracks), badger Meles meles (16 observations, 22 tracks), stone marten Martes foina (18 observations, 41 tracks) and roe deer Capreolus capreolus (20 observations, 41 tracks). The roe deer records were all accounted for by a single male, with other animals present in the area not using the underpass. Three brown hares Lepus europaeus were observed entering the underpass, but all turned around and did not pass through. The entrance of a tunnel underpass (13 m wide, 7.5 m high, 155 m long) was monitored using a video camera and two infra-red lamps for 30 days in April–May and in August–September 1997 (total 495 hours). Tracks in sand at either end of the stream through the underpass were recorded daily. There was 1.8-m-high fencing both sides of the highway, for 1 km in each direction from the underpass.

  • 123 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicl (...)

199A before-and-after study in 1981–1999 in temperate mixed woodland forest and grassland in Alberta, Canada123 found that underpasses and overpasses, along with roadside fencing, reduced road deaths of large mammals. Wildlife-vehicle collisions were significantly lower during the two years after fencing (5–28/year) compared to the two years before (18–93/year) for all three road sections, despite an increase in traffic flow. Ungulate casualties declined by 80 %. Species included coyote Canis latrans, black bear Ursus americanus, wolf Canis lupus, bighorn sheep Ovis canadensis, moose Alces alces, deer Odocoileus spp. and elk Cervus canadensis. Most road deaths were within 1 km of the end of the fences. Deaths also occurred close to drainage structures. The Trans-Canada highway was expanded to four lanes and had 2.4-m-high wildlife exclusion fence installed in three phased sections, completed in 1984 (10 km), 1987 (16 km) and 1997 (18 km). Twenty-two wildlife underpasses and two overpasses were constructed along these sections. Wildlife-vehicle collisions were monitored from May 1981 to December 1999.

  • 124 Abson R.N. & Lawrence R.E. (2003) Monitoring the use of the Slaty Creek wildlife underpass, Calder (...)

200A study in 2002–2003 of a highway bisecting forest blocks in Victoria, Australia124 found that an underpass, along with roadside fencing, was used by 13 native mammal species. These comprised 76 % of mammal species recorded in the adjacent forest (bats not included). The underpass was used by koalas Phascolarctos cinereus, wombats Lasiorhinus latifrons, echidnas, macropods (e.g. kangaroos, wallabies), rodents and carnivorous marsupials (four of five species), and gliders and possums (four of seven species). In 1997, a 70-m wide underpass was built under a split dual-carriageway bridge. Some vegetation was retained and some planted within the underpass. Barrier fencing, 2 m high, ran the length of the highway (with koala escape poles). Intensive sampling was carried out for one week/month in July 2002–June 2003, within the underpass and at two forest sites, 100 m and 320 m from the underpass. Small mammal traps, hair tubes, nest boxes for arboreal mammals, spotlight counts, track surveys and scat surveys were used to monitor wildlife.

  • 125 Brudin C.O. (2003) Wildlife use of existing culverts and bridges in north central Pennsylvania. Pro (...)

201A replicated study in 2000–2003 along a highway in Pennsylvania, USA125 found that a range of mammals used box culverts and bridge underpasses, some of which were in areas with roadside fencing. In the first phase, eight of nine culverts were used by mammals, with white-tailed deer Odocoileus virginianus (one culvert), raccoon Procyon lotor (seven), opossum Didelphis marsupialis (two), feral cat Felis catus (one), long-tailed weasel Mustela frenata (one), red fox Vulpes fulva (one), striped skunk Mephitis mephitis (one) and black bear Ursus americanus (one) recorded. In the second phase, white-tailed deer used nine of 20 larger culverts (with higher cross-section: length ratios). Black bears, opossums, raccoons and muskrats Ondatra zibethicus also used these culverts. Deer did not use culverts >90 m long, but use was not affected by substrate (concrete, natural or water). In September–November 2000, nine culverts were monitored using infrared-triggered cameras. Approximately half of the culverts had sediment on their floors. Twenty larger culverts that were considered suitable for deer (out of 70) were monitored using cameras, 10 in September–November 2002 and 10 in May–July 2003. Entrances to 13 of these were separated from roads by right-of-way fencing.

202A before-and-after study in 2002–2003 along a highway in Arizona, USA (16; same experimental set-up as 25) found that two open-span bridge underpasses, in areas with roadside elk-proof fencing, were used by elk Cervus canadensis but not by white-tailed deer Odocoileus virginianus and vehicle-deer collisions did not decrease after installation. A total of 181 collisions were reported, with no difference in rates along the section before and after the two underpasses were constructed. GPS collars recorded 675 highway crossings by elk, only 6 % of which were through underpasses. Overall, 62 % of 1,435 elk, but only 0.4 % of 257 white-tailed deer recorded on cameras at underpasses crossed through them. Two open-span bridge underpasses (<250 m apart) along the State Route 260 highway were monitored using video cameras and track counts (inside and 60 m from entrances). Cameras were also installed at the ends of the short sections of elk-proof fencing. Thirty elk were tracked using GPS collars (May 2002 to July 2003). Vehicle-deer collisions were recorded before and after underpass installation.

  • 126 Gordon K.M. & Anderson S.H. (2003) Mule deer use of underpasses in western and southeastern Wyoming(...)

203A study in 2001–2003 along two highways in Wyoming, USA126 found that use of underpasses, in areas with roadside fencing, by mule deer Odocoileus hemionus decreased with a decrease in underpass width. Only one of the six underpasses was consistently used by mule deer, accounting for 91 % of the 1,028 recorded crossings made through all underpasses. It had a high cross section: length ratio and was near a historic migration route. At an experimental underpass, the percentage of deer turning away from the underpass increased significantly as the cross section: length ratio decreased. Six (of 12) underpasses along a section of Interstate 80 were monitored. Four were box type and two were small gravel road underpasses. Use was assessed using infrared-triggered cameras and track surveys. One experimental underpass was installed in 2001. It was 18 m long. The width was experimentally manipulated from 3–6 m and height from 2–3 m. Video cameras recorded deer behaviour. Underpasses were monitored from autumn 2001 to spring 2003. Fences, 2.4 m high, ran alongside the highway.

  • 127 Plumb R.E., Gordon K.M. & Anderson S.H. (2003) Pronghorn use of a wildlife underpass. Wildlife Soci (...)

204A study in 2001–2002 along a highway in Wyoming, USA127 found that an underpass, in an area with roadside deer-proof fencing, was used by pronghorn Antilocapra americana. A total of 70 pronghorns passed through the underpass over 11 occasions between December and April (group size 1–57). These animals did not hesitate before crossing. An additional 19 pronghorns approached the structure but did not cross. All but two crossings took place at dusk or pre-dawn and most were in the presence of mule deer Odocoileus hemionus. A 2.4-m-high deer-proof fence was constructed in 1989 alongside 11 km of United States Highway 30. In 2001, a wildlife underpass was constructed. Underpass use was monitored using motion sensors with infrared-triggered cameras at either end from October 2001 to May 2002.

  • 128 Servheen C., Shoemaker R. & Lawrence L. (2003) A sampling of wildlife use in relation to structure (...)

205A study in 2002–2003 along a highway in Montana, USA128 found that seven bridge underpasses, in areas with roadside fencing, were used by white-tailed deer Odocoileus virginianus, mule deer Odocoileus hemionus and elk Cervus canadensis. White-tailed deer were photographed 791 times, mule deer 379 times and elk 100 times. Between 38 and 430 deer were recorded at each underpass, but none in culverts. Smaller numbers were recorded of striped skunk Mephitis mephitis (nine photographs), raccoon Procyon lotor (three), red fox Vulpes vulpes (one), coyote Canis latrans (three) and black bear Ursus americanus (one). There were no significant relationships between wildlife use and underpass structural features. Distribution of mammal road deaths was independent of underpass locations. Seven bridge underpasses and three culverts were monitored along an 80-km highway section from October 2002 to July 2003. Crossings connected with roadside fencing, though this was inadequately maintained and was permeable to deer. Heat-and motion-sensitive cameras were used at underpasses (for 101–700 camera days/ underpass). Details about location, structure, vegetation cover and human activities were recorded for each underpass. Road deaths were opportunistically recorded and combined with data collected by road maintenance crews (spanning 1998–2002).

  • 129 Taylor B.D. & Goldingay R.L. (2003) Cutting the carnage: wildlife usage of road culverts in north-e (...)

206A study in 2000–2001 in coastal lowlands in New South Wales, Australia129 found that concrete wildlife culverts, in areas with roadside fencing, were used by small and medium-sized mammals. Mammal tracks made up 82 % of all vertebrate tracks recorded. These were made by bandicoots Perameloidea (25 % of all tracks), rats (25 %), wallabies (13 %), mice Muridae (10 %), feral cat Felis catus (<2 %) and red foxes Vulpes vulpes (<2 %). Koala Phascolarctos cinereus tracks were recorded twice. In cage traps, house mouse Mus musculus (29 individuals) and swamp rat Rattus lutreolus (16 individuals) were the most common among six species (67 individuals) caught. Nine concrete culverts along a 2.5-km section of highway were monitored. They were 2.4 m wide, 1.2 m high and 18 m long. A 1.8-m-high fence ran along either side of the road. Tracks were recorded on sand in culverts from 22–30 September 2000 and 1–9 December 2000. Between 15 and 17 cage traps were set in and next to each culvert on four nights in September 2000 (560 trap-nights).

  • 130 Dodd C.K., Barichivich W.J. & Smith L.L. (2004) Effectiveness of a barrier wall and culverts in red (...)
  • 131 Dodd N.I., Gagnon J.W., Manzo A.I. & Schweinsburg R.E. (2007) Video surveillance to assess highway (...)
  • 132 Benten A., Hothorn T., Vor T. & Ammer C. (2018) Wildlife warning reflectors do not mitigate wildlif (...)
  • 133 Rogers E. (2004) An ecological landscape study of deer vehicle collisions in Kent County, Michigan. (...)

207A study in 2001–2002 along a highway in Florida, USA130 found that culverts, in areas with roadside barrier walls, were used by mammals but road casualties still occurred. Ten mammal species (and one species pair) were recorded using culverts. These included rice rat/ hispid cotton rat Oryzomys palustris/Sigmodon hispidus (in five culverts), cotton mouse Peromyscus gossypinus (three culverts), round-tailed muskrat Neofiber alleni (three culverts) and southeastern short-tailed shrew Blarina carolinensis (two culverts). Other species used one culvert each. During the same period, ≥13 mammal species were recorded dead on the road. The most frequent casualties were rice rat131, Virginia opossum Didelphis virginianus 132and nine-banded armadillo Dasypus novemcinctus 133. Culverts reduced overall vertebrate road mortality, but separate mammal figures were not reported for before culverts were installed. Eight culverts (from 0.9 m diameter to 2.4 × 2.4 m cross-section, all 44 m long) were connected using prefabricated concrete barrier walls. Culverts were monitored from 14 March 2001 to 5 March 2002 using funnel traps, camera traps and sand track stations. Roadkills were monitored by walking the 3.2-km road over three consecutive days each week.

  • 134 McDonald W. & St Clair C.C. (2004) Elements that promote highway crossing structure use by small ma (...)

208A study in 1999–2000 in Alberta, Canada134 found that small culverts, in areas with roadside barrier fencing, were used by mice and voles more than were larger underpasses. More translocated animals returned to their capture location through 0.3-m-diameter culverts (deer mice Peromyscus maniculatus: 100 % returned; red-backed voles Clethrionomys gapperi: 86 %; meadow voles Microtus pennsylvanicus: 58 %) than through 3-m-wide underpasses (69, 49, 10 % respectively). More animals successfully returned through underpasses (and overpasses) with 100 % vegetation cover at entrances (55–100 % of animals returned) compared to those with 50 % (20–76 %) or no cover (0–66 %). Animals crossed within 1–4 days. Nine vegetated soft-bottomed, unvegetated arch-shaped underpasses (64–73 m long) and nine metal drainage culverts with grass cover (63–72 m long) were studied. Crossings were linked to roadside fencing that limited movements of large animals. Territorial mice and voles were captured using Longworth live traps (166 caught), ear-tagged, coated with fluorescent powder, taken across the road, released at standardized distances from crossings (20, 40, 60 m) and followed as they returned. Vegetation cover 2 m inside and outside entrances was varied using spruce branches to 100 %, 50 % and no cover. Traps at original capture sites were monitored for four days after translocation. Monitoring was undertaken in July–October 1999 and 2000.

  • 135 Clevenger A.P. & Waltho N. (2005) Performance indices to identify attributes of highway crossing st (...)
  • 136 Gagnon J.W., Dodd N.L., Ogren K.S. & Schweinsburg R.E. (2011) Factors associated with use of wildli (...)

209A study in 1997–2000 of a highway in Alberta, Canada135 found that underpasses, in areas with roadside fencing, were used by large mammals. The 11 underpasses were visited by elk Cervus canadensis (1302 records), deer Odocoileus sp. (543), cougars Puma concolor (105), black bears Ursus americanus (103), wolves Canis lupus 136and grizzly bears Ursus arctos (six). The majority of animals that visited underpasses crossed through the structures. Underpass height and width were both positively correlated with the number of animals using them. Two bridge underpasses (3 m high, 11 m wide), four concrete box underpasses (2.5 × 3.0 m) and five metal culverts (4 m high, 7 m wide) were monitored along an 18-km stretch of the four-lane Trans-Canada Highway. Barrier fencing, 2.4 m high, ran along the highway. Tracks were monitored at each end of each crossing, in a 2 × 4-m sand, silt and clay tracking station, every 3–4 days from November 1997 to August 2000. Information about each structure, the surrounding landscape, and human activity were recorded for each underpass.

  • 137 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2005) Complementary use by vertebrates of cr (...)

210A study in 2002 of a highway in Zamora, Spain137 found that underpasses and culverts, in areas with roadside barrier fencing, were used by mammals. Circular culverts were used by hedgehog Erinaceus europaeus, garden dormouse Eliomys quercinus, badger Meles meles, common genet Genetta genetta and red fox Vulpes vulpes. Adapted (enlarged) culverts were used by red squirrel Sciurus vulgaris, badger and red fox. Open-span underpasses were used by hedgehog, badger, red fox and red deer Cervus elaphus. Wildlife underpasses were used by hedgehog, badger, common genet and red fox. Crossings were also used by rodents and shrews, rabbit Oryctolagus cuniculus, Iberian hare Lepus granatensis, weasel Mustela nivalis, European wildcat Felis silvestris and wolf Canis lupus (see paper for details). Sixty-four underpasses/culverts (30–150 m long) under a 72-km section of motorway were monitored. These included 33 circular drainage culverts (2 m diameter), 10 wildlife-adapted box culverts (2–3 m wide, 2 m high), 14 open-span underpasses (rural tracks/paths, 4–9 m wide, 4–6 m high) and seven wildlife underpasses (20 m wide, 5–7 m high). The motorway was barrier-fenced. Animal tracks were monitored over 10 days in June–September 2002 using marble dust (1-m-wide cross). Camera traps verified species identifications in some underpasses.

  • 138 Dodd N.I., Gagnon J.W., Manzo A.I. & Schweinsburg R.E. (2007) Video surveillance to assess highway (...)

211A study in 2002–2005 along a highway through riparian meadows in Arizona, USA138 found that two open-span bridge underpasses, in areas with roadside ungulate-proof fencing, were used by Rocky Mountain elk Cervus canadensis nelsoni, with a more open, shorter underpass with natural sides being used most frequently. In total, 3,708 elk, in 1,266 groups, were recorded at the two underpasses (91 % of all mammals recorded) with 2,612 elk in 905 groups passing through the underpasses. More elk groups passed through the shorter underpass (663 groups) than through the longer underpass (242 groups). Seven additional mammal species were recorded at the two underpasses (species not stated in paper). Two open-span bridge underpasses (<250 m apart), along the State Route 260 highway, were studied. Fencing, 2.4 m high, along 0.6 km of highway, funneled animals towards underpasses. Underpasses were monitored using four video cameras, in September 2002 to September 2005. The shorter underpass was 7 m high, 10 m wide and 53 m long, with open, natural sides. The longer underpass was 12 m high, 16 m wide and 111 m long, with concrete walls.

  • 139 Ascensão F. & Mira A. (2007) Factors affecting culvert use by vertebrates along two stretches of ro (...)

212A replicated study in 2004 along two roads through agricultural land in Alentejo, Portugal139 found that all 34 monitored culverts, some in areas with roadside fencing, were used by mammals. Crossings were made by small mammals (289 crossings, 34 culverts), hedgehogs Erinaceus europaeus (55 crossings, 15 culverts), hares and rabbits (71 crossings, 15 culverts), weasels Mustela nivalis (16 crossings, 9 culverts), stone martens Martes foina (93 crossings, 28 culverts), Eurasian badgers Meles meles (55 crossings, 10 culverts), otters Lutra lutra (2 crossings, 2 culverts), common genets Genetta genetta (65 crossings, 20 culverts), Egyptian mongooses Herpestes ichneumon (82 crossings, 21 culverts) and red foxes Vulpes vulpes (27 crossings, 12 culverts). A total of 34 culverts (<1.0 m wide, 8–25 m long) were monitored along two roads (17 culverts along each). Road sections studied were 16 and 30 km long. There was 1.5-m-high roadside fencing along the 30-km section. Tracks were monitored using marble dust (60–100 cm wide) which was placed inside each end of each culvert. Tracks were recorded on four days in each of spring, summer and autumn 2004 (total 408 culvert monitoring days).

  • 140 Baker A., Knowles M. & Latham D. (2007) Using clay drain seals to assess the use of dry culverts in (...)

213A study in 2007 along a road, in Northumberland, UK140 found that three underpasses, with entrances fenced off from the road, were used by several species of small and medium-sized mammals to make crossings. Tracks were identified of western hedgehog Erinaceus europaeus, brown rat Rattus norvegicus, badger Meles meles and American mink Mustela vison. The number of underpasses used and frequency of use was not detailed in the paper. Underpasses, 0.6–0.9 m wide, were constructed in 2003–2006 along a 46-km stretch of road and were fenced off from the road. Mammal use was monitored in August–October 2007. Clay-based drain seals (45 × 45-cm surface and 0.5 cm thick), used as footprint pads, were placed at entrances to three dry culverts and checked weekly for footprints.

  • 141 Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Electric fencing (...)

214A before-and-after study in 1990–2005 along a highway in Québec, Canada141 found that an underpass was used by moose Alces alces and, along with electric fences, it reduced moose-vehicle collisions. Twenty-three sets of moose tracks were recorded in the underpass over three years. There were fewer moose-vehicle collisions after fence construction (zero) than before (1.4/year). An underpass (23 m long, 16 m wide, 7 m high) was established along both side of a river, under a bridge along the highway. Electric fences (1.5 m high, wires 0.3 m apart) were installed along both sides of a 5-km highway section, encompassing the underpass, in 2002. Data on moose-vehicle collisions before fence installation were collated by the Ministère des Transports du Québec, between 1990 and 2002. Details of monitoring collisions after installation are not given.

  • 142 Bond A.R. & Jones N.J. (2008) Temporal trends in use of fauna-friendly underpasses and overpasses. (...)
  • 143 Gordon K.M. & Anderson S.H. (2003) Mule deer use of underpasses in western and southeastern Wyoming(...)
  • 144 Dodd N.L., Gagon J.W. & Schweinsburg R.E. (2003) Evaluation of measures to minimize wildlife-vehicl (...)
  • 145 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyom (...)
  • 146 Reed D.F. (1981) Mule deer behavior at a highway underpass exit. The Journal of Wildlife Management(...)

215A before-and-after study in 2004–2007 along a highway through eucalypt woodland in Queensland, Australia142 found that two underpasses, in areas with roadside barrier fencing, were used by mammals and the mammal road casualty rate fell after construction. There were three wild mammal road casualties over 29 months post-construction and six during four months pre-construction. This comparison was not tested for statistical significance. Tracks detected in underpasses were from rodents (370 tracks), house mice Mus musculus (115), Dasyurid sp. (most likely Common dunnart Sminthopsis murina)143, northern brown bandicoots Isoodon macrourus (179), possums144, red-necked wallabies Macropus rufogriseus 145, short-beaked echidnas Tachyglossus aculeatus 146and from feral cats Felis catus, dogs Canis lupus familiaris and brown hares Lepus europaeus. Proportions of tracks representing full crossings varied by species with the highest figure for wild mammals being for possums (18–40 % of records). In 2004, a 1.3-km section of highway was upgraded to four lanes and a variety of wildlife crossings constructed, linked by barrier fencing (2.5 m high). Use of two underpasses (2.4 m high, 2.5 m wide, 48 m long) with water flowing through and ledges attached to side walls, was monitored, starting six months after construction. Tracks were counted on sand within each entrance, twice weekly from August 2005–February 2006 and monthly from June 2006–June 2007. Road-kill was monitored twice weekly before (April–July 2004) and weekly after construction until June 2007.

  • 147 Braden A.W., Lopez R.R., Roberts C.W., Silvy N.J., Owen C.B. & Frank P.A. (2008) Florida Key deer O (...)

216A before-and-after study in 1996–2004 in Florida, USA147 found that two underpasses, along with roadside barrier fencing, reduced Florida Key deer Odocoileus virginianus clavium collisions with vehicles by 94 %. There were 2 collisions/year over two years after fence construction compared to 12–20 collisions/year over five years before construction (total 79 collisions). Underpass use increased over time, with 22 photographs of deer/month over the first six months and 59/month over the following six months. Average annual deer ranges and core areas did not change after underpass construction. Only 45 % (5/11) of radio-collared deer were located on both sides of the highway after construction compared to 100 % (9/9) before. In 2002, two box underpasses (14 × 8 × 3 m) were constructed with 2.6-km-long barrier fencing (2.4 m high) and four deer guards (modified cattle guards) installed between them, along a two-lane highway. Deer mortalities on roads were recorded from 1996, by direct sightings, law enforcement reports and observations of vultures. Underpass use was monitored using infrared-triggered cameras from February 2003–January 2004. Deer were radio-tracked between January 1998 and December 2000 (44 deer) and between February 2003 and January 2004 (32 deer) and were located 6–7 times/week.

  • 148 Grilo C., Bissonette J.A., and Santos-Reis M. (2008) Response of carnivores to existing highway cul (...)

217A replicated study in 2004 along two roads in southern Portugal148 found that underpasses and culverts along roads bounded by livestock fencing were used by carnivore species to cross highways. Crossing rates of underpasses were similar to those of culverts for red fox Vulpes vulpes (underpasses: 0.25 crossings/day; culverts: 0.11), badger Meles meles (underpasses: 0.30; culverts: 0.15), genet Genetta genetta (underpasses: 0.15; culverts: 0.9) and Egyptian mongoose Herpestes ichneumon (underpasses: 0.29; culverts: 0.22). Stone marten Martes foina used underpasses more (0.22 crossings/day) than they used culverts (0.05 crossings/day). Fifty-seven passages under 252 km of two major roads were monitored. They comprised 1.2 circular culverts/km (1 and 1.5 m diameters), 0.3 box culverts/km (2 × 2 m to 5 × 5 m), and 0.5 underpasses/km (5 m high and 8 m wide). Crossing structures were 5–1,566 m apart. Livestock fencing, 1.5 m high, ran along both sides of both roads. A 1-m2 plot of marble dust was placed at each end and in the middle of each passage. This was checked for tracks every five days, over 20 consecutive days of monitoring, in both spring and summer 2004.

  • 149 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2008) Are motorway passages worth building? (...)

218A study in 2001 along a highway in Zamora province, Spain149 found that road underpasses and culverts, in areas with roadside barrier fencing, were used by mammals. Wildlife underpasses were the most used out of four structure types, by polecats Mustela putorius (detected on average on 0.2/10 days/underpass), roe deer Capreolus capreolus (0.4/10), red deer Cervus elaphus (0.4/10), wild boar Sus scrofa (0.6/10) and rabbits and hares (1.2/10). Open-span underpasses was the most used structure by small-spotted genets Genetta genetta (0.3/10) and red foxes Vulpes vulpes (4.7/10). European badgers Meles meles (3.1/10) and rats (0.4/10) used wildlife-adapted box culverts more than other structure. Small mammals (1.6/10) were most frequently recorded in circular culverts. Thirty-three crossings were monitored. These comprised five wildlife underpasses (14–20 m wide, 5–8 m high, 30–96 m long), seven open-span underpasses (rural tracks/paths, 4–9 m wide, 4–6 m high, 32–72 m long), seven wildlife-adapted box culverts (2–4 m wide, 2–3 m high, 36–45 m long) and 14 circular drainage culverts (2 m diameter, 35–62 m long). The motorway had barrier fencing along its length. Animal tracks were recorded using marble dust (1-m-wide cross) over 10 days in March–June 2001.

  • 150 Olsson M.P.O. & Widen P. (2008) Effects of highway fencing and wildlife crossings on moose Alces al (...)

219A before-and-after study in 2002–2005 along a highway through mixed forest and farmland in southwestern Sweden150 found that following installation of an underpass, overpasses and barrier fencing, moose Alces alces road casualties declined but moose did not use the underpass. There were fewer moose-vehicle collisions after fence construction (zero/year) than before (2.7/year). During construction, 1.8 collisions/year were recorded. Moose were recorded crossing the highway 47 times before construction of crossing features, 76 during and 12 times after features were installed. All crossings after fencing prevented direct road access were via the two wildlife overpasses. Two 6-km sections of a highway were converted to a fenced four-lane highway in 2000–2004. The sections contained one wildlife underpass (35 m long, 4.7 m high, 13 m wide), two wildlife overpasses, three conventional road tunnels and two conventional bridges that could be crossed. Twenty-four moose were radio-collared. Locations were recorded every two hours before construction (February–September 2002), during construction (October 2002–May 2004) and after construction (June 2004–December 2005; 8,830 moose days).

  • 151 Olsson M.P.O., Widen P. & Larkin J.L. (2008) Effectiveness of a highway overpass to promote landsca (...)

220A before-and-after study in 2000–2005 in forest and farmland in southwestern Sweden151 found that barrier fencing and three road crossings reduced moose Alces alces and roe deer Capreolus capreolus road-kills. Deaths were reduced 70 % from averages of 2.7 moose killed/year and 5.3 roe deer killed/year over the 12 years pre-construction. In 2000–2004, a 12-km section of the European Highway 6 was converted from two to four lanes and 2.2-m-high exclusion fencing was installed along its length. Two overpasses and one underpass were also constructed. Moose and deer casualty rates were collated from casualties reported to police pre-construction (1990–2001) and post-construction (up to 2005).

  • 152 Parker I.D., Braden A.W., Lopez R.R., Silvy N.J., Davis D.S. & Owen C.B. (2008) Effects of US 1 Pro (...)

221A before-and-after study in 1996–2005 along a highway in Florida, USA152 found two underpasses with associated barrier fencing reduced vehicle collisions with Florida Key deer Odocoileus virginianus clavium. Fewer deer were killed on the fenced road section after underpass and fence installation (0–3/year) than before (11–20/year). There were more collisions on unfenced road sections after installation (40/year) than before (24/year), so collisions were not reduced overall. However, deer densities increased and the ratio of collisions to deer numbers suggested that risks of collisions decreased after construction. Deer use of two underpasses increased from the first year after construction (871 detections) to the second and third years (1,857 and 1,629 deer detections respectively). A 2.6-km-long system with two underpasses (dimensions not stated), 2.4-m-high fencing and four deer guards were constructed on US Highway 1. An infrared trail monitor and camera monitored deer passages at the centre of each underpass for three years post-construction (2003–2005). Deer-vehicle collisions were recorded (from 1996) from direct sightings, citizen and law enforcement reports and observations of vultures before (1996– 2000) and after (2003–2005) fence and underpass construction.

  • 153 Hayes I. & Goldingay R.L. (2009) Use of fauna road-crossing structures in north-eastern New South W (...)

222A site comparison study in 2006 along a Highway in New South Wales, Australia153 found that two underpasses were used by mammals and that presence of crossing-structures along with barrier fencing reduced road-kills. There were fewer road-kills over seven weeks along the section with crossing-structures (0.02/km of survey) than along a section without crossings (0.09/km of survey). The most frequently recorded road casualties were bandicoots (16 casualties) and kangaroos and wallabies (nine casualties). Bandicoots used the two underpasses more than they used the two overpasses (87 vs 28 tracks) as did rodents (82 vs 15). Kangaroos and wallabies used underpasses less than they used overpasses (36 vs 104 tracks). Use was similar between structure types for possums (14 vs 9). There were two concrete box culverts (3 × 3 m, 42–63 m long) and two wildlife bridges (9–37 m wide, with vegetation) with 5 km of exclusion fencing, along a 12-km section of dual-carriageway highway. Tracks were monitored on sand plots across each crossing. Road-kill surveys were conducted along the 12-km section and along a 51-km two-lane section without crossings or fencing. Track and road-kill surveys were conducted up to three times/ week over seven weeks in August–September 2006.

  • 154 Klar N., Herrmann M. & Kramer-Schadt S. (2009) Effects and mitigation of road impacts on individual (...)

223A study in 2001–2005 along a motorway through forest and agricultural land in Germany154 found that most underpasses and overpasses, in areas with roadside fences, were used by wildcats Felis silvestris to cross roads. Wildcats used crossing structures on 18 of the 21 occasions on which they were recorded <50 m from the motorway. The three underpasses were each used by one cat from a total of eight wildcats that had underpasses located within their home ranges. One 40-m-wide underpass and two road underpasses (9–14 m wide), along with two open-span viaducts and two forest road overpasses, were monitored in 2002–2005. All underpasses were 29 m long. Underpasses were connected to fencing that was designed specifically to exclude wildcats from the road. Twelve wildcats were radio-collared between January 2001 and February 2005. Animals were tracked at night for 3–30 months each.

  • 155 Kusak J., Huber D., Gomerčić T., Schwaderer G. & Gužvica G. (2009) The permeability of highway in G (...)
  • 156 Mathiasen R. & Madsen A.B. (2000) Infrared video-monitoring of mammals at a fauna underpass. Intern (...)
  • 157 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass (...)
  • 158 Singer F.J. & Doherty J.L. (1985) Managing mountain goats at a highway crossing. Wildlife Society B (...)
  • 159 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass (...)
  • 160 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass (...)

224A study in 1999–2001 along a road through beech and fir forest in Gorski kotar, Croatia155 found that an underpass below a section of road on a viaduct, and separated from the road by barrier fencing, was used by medium to large-sized mammals. Tracks were recorded of roe deer Capreolus capreolus (total 20 tracks), red deer Cervus elaphus 156wild boar Sus scrofa 157, brown bear Ursus arctos 158, grey wolf Canis lupus 159and Eurasian lynx Lynx lynx 160. However, the underpass had five times fewer mammal crossings/day than did three overpasses (100–835 m wide). A new highway was constructed in 1998–2004 with 44 wildlife crossings and 2.1-m barrier fencing along a 9-km section. An underpass (569 m wide, below a 25-m-high road viaduct) was monitored. Tracks (in snow, mud or sand) and other animal signs were counted 23 times in January 1999–January 2001.

  • 161 McCollister M.F. & van Manen F.T. (2010) Effectiveness of wildlife underpasses and fencing to reduc (...)
  • 162 Brudin C.O. (2003) Wildlife use of existing culverts and bridges in north central Pennsylvania. Pro (...)
  • 163 Clevenger A.P. & Waltho N. (2000) Factors influencing the effectiveness of wildlife underpasses in (...)

225A site comparison study in 2000–2007 along a highway in North Carolina, USA161 found that underpasses and barrier fencing facilitated road crossings by a range of mammals but did not reduce road casualties. Camera traps showed crossings through the three underpasses by white-tailed deer Odocoileus virginianus (2,258 times), raccoon Procyon lotor (125), American black bear Ursus americanus 162, bobcat Lynx rufus 163, grey fox Urocyon cinereoargenteus (eight), Virginia opossum Didelphis virginiana (six), rabbits Sylvilagus spp. (two) and Canis spp. (two). Track counts indicated an additional 3,552 mammal crossings by 15 species, with 90 % by white tailed deer. A similar number of mammals was killed over one year on road sections with underpasses and fencing (5.0/km) as on sections without (5.1/km). A four-lane highway was constructed with three underpasses. Barrier fencing, 3 m high, was installed ≥800 m along the highway from each underpass. Gates allowed trapped animals to escape the highway. Underpass use was monitored by 2–3 camera traps /underpass. Twice-weekly track surveys were conducted (on 2.5-m-wide plates across underpasses). Road deaths were recorded along 6 km of road with fencing and underpasses and 11 km without, twice/week, from July 2006–July 2007.

  • 164 Taylor B.D. & Goldingay R.L. (2010) Roads and wildlife: impacts, mitigation and implications for wi (...)

226A review of 30 papers reporting on monitoring of 329 crossing structures in Australia, Europe and North America164 found that mammals used most culverts and underpasses, among which some were in areas with roadside barrier fencing. Small mammals used pipes (demonstrated by 6/7 relevant studies), drainage culverts (5/5 studies), adapted culverts (5/5 studies), wildlife underpasses (3/4 studies) and bridge underpasses (2/3 studies). Arboreal mammals used pipes (1/1 studies), drainage culverts (4/4 studies), adapted culverts (4/4 studies) and bridge underpasses (1/1 studies). Medium-sized mammals used pipes (8/11 studies), drainage culverts (12/13 studies), adapted culverts (8/8 studies), wildlife underpasses (6/8 studies) and bridge underpasses (6/7 studies). Large mammals used pipes (6/9 studies), drainage culverts (11/12 studies), adapted culverts (11/11 studies), wildlife underpasses (24/24 studies) and bridge underpasses (14/15 studies). Larger mammals tended to use more open underpasses. Small and medium-sized mammals used underpasses with funnel-fencing or adjoining walls and those with vegetation cover close to entrances. Those with vegetation cover tended to be avoided by some ungulates. Thirty papers reporting monitoring of 329 crossing structures were reviewed. Fourteen papers investigated multiple structure types, resulting in a total of 52 studies of different structure types. Underpasses, from small drainage pipes to dry passage bridges, comprised 82 % of crossings.

  • 165 Dodd N.L., & Gagnon J.W. (2011) Influence of underpasses and traffic on white-tailed deer highway p (...)

227A study in 2003–2007 at six sites along a highway through forest and shrubland in Arizona, USA165 found that underpasses, in areas with ungulate-proof fencing, were used by white-tailed deer Odocoileus virginianus and that underpass use was not affected by traffic levels. Crossing rates of white-tailed deer that approached underpasses did not differ significantly between traffic volume levels of 0 vehicles/minute (0.28 crossings/approach), 1–2 vehicles/minute (0.34 crossings/approach), 2–4 vehicles/minute (0.40 crossings/ approach), 4–6 vehicles/minute (0.27 crossings/approach) and >6 vehicles/minute (0.28 crossings/approach). Deer passage rates and traffic flows were monitored at six wildlife underpasses beneath 27 km of an upgraded four-lane highway. Underpasses were 53–128 m long and 5–15 m high. Five underpasses had a fenced above-ground section (11–48 m long) between the two carriageways. Roadside fencing, 2.4 m high, was gradually installed with the full road section fenced by 2006. Four video cameras with infrared beams monitored traffic and deer at each underpass in 2003–2007. The number of deer approaching within 50 m of underpasses and the number crossing the highway through underpasses was counted.

  • 166 Eldridge B. & Wynn J. (2011) Use of badger tunnels on Highway Agency schemes in England. Conservati (...)

228A replicated study in 2010 at 38 sites along nine roads in England, UK166 found that underpasses, in areas with roadside fencing, were used by badgers Meles meles, Eurasian otters Lutra lutra, red foxes Vulpes vulpes, European hedgehogs Erinaceus europaeus and brown rats Rattus rattus to cross roads. Of 38 underpasses monitored, 34 were used by badgers. Eurasian otters, red foxes, European hedgehogs and brown rats used underpasses, but the number of underpasses used or crossing frequencies are not reported. Badger footprints were recorded 7–8 times in 14 underpasses, 4–6 times in 11 underpasses and 1–3 times in 9 underpasses. Mammals were monitored in 38 underpasses, installed in 2003–2007, under single carriageway roads (16 underpasses), dual carriageways (20 underpasses), a motorway (one underpass) and a junction (one underpass). Underpasses were 20–120 m long, 0.3–1 m in diameter (most were 0.6 m diameter) and were made of concrete and corrugated iron. Roadside fence characteristics are not specified. Mammals were surveyed weekly, between August and October 2010, by monitoring footprints in a clay mat (45 × 45 cm) at the entrance of each underpass.

  • 167 Gagnon J.W., Dodd N.L., Ogren K.S. & Schweinsburg R.E. (2011) Factors associated with use of wildli (...)

229A replicated study in 2002–2008 along a highway in Arizona, USA167 found that wildlife underpasses, in areas with roadside ungulate-proof fencing, were used by mammals. Six underpasses were approached 14,683 times by wild mammals, of 15 species. Of all animals recorded (which included also 450 records of domestic animals and one of a bird) 72 % crossed through underpasses. Elk Cervus canadensis accounted for 70 % of visits by wild mammals to underpasses, white-tailed deer Odocoileus virginianus for 13 % and mule deer Odocoileus hemionus for 7 %. Other crossings comprised coyote Canis latrans (1 %), grey fox Urocyon cinereoargenteus (2 %), raccoon Procyon lotor (2 %) and other mammals (4 %). Reconstruction of a 27-km stretch of State Route 260 was undertaken in 2000–2006 and included creation of 11 large wildlife underpasses, connected to ungulate-proof fencing. Six underpasses (34–41 m wide, 5–12 m high and 53–128 m long) were monitored for an average 4.7 (2.5–5.5) years using animal-triggered multi-camera video surveillance.

  • 168 Parker I.D., Lopez R.R., Silvy N.J., Davis D.S. & Owen C.B. (2011) Long-term effectiveness of US 1  (...)

230A before-and-after, site comparison study in 1996–2009 along a highway through woodland and developed areas in Florida, USA168 found that underpasses beneath the highway, along with roadside fencing, reduced vehicle collisions with Florida Key deer Odocoileus virginianus clavium. Fewer deer were killed on the road over seven years after underpass and fence installation (1.6/year) than in the five years before installation (15.6/ year). Concurrently, along an unfenced section without underpasses, 43 deer/year were killed in the latter period and 24/year were killed in the earlier period. Underpass use increased from 185 passages during the first year after construction to 1,337 passages in the seventh year after construction. A highway was upgraded to increase vehicle capacity, with construction completed in 2002. Two box culvert underpasses (14 m long, 8 m wide, 3 m high) were installed under a 2.6-km-long fenced road section through undeveloped land. Deer-vehicle collisions were monitored along this section and along an adjacent 3.0-km-long unfenced section through a developed area, before culvert installation (1996–2000) and after (2003–2009). Culvert use was monitored using camera traps.

  • 169 Sawyer H., Lebeau C. & Hart T. (2012) Mitigating roadway impacts to migratory mule deer—a case stud (...)
  • 170 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicl (...)
  • 171 Clevenger A.P. (1998) Permeability of the Trans-Canada highway to wildlife in Banff National Park: (...)
  • 172 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicl (...)
  • 173 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyom (...)
  • 174 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass (...)

231A before-and-after study in 1990–2011 of scrubland in Wyoming, USA169 found that underpasses beneath a highway, in areas with roadside game-proof fencing, were extensively used by mule deer Odocoileus hemionus and collisions between deer and vehicles reduced. Over three years, 49,146 mule deer were recorded moving through seven underpasses. Passage rates through underpasses of deer approaching to ≤50 m increased over three years, from 54 % to 92 %. After underpass construction, there were 1.8 collisions/month between deer and vehicles compared to 9.8 collisions/month before. Underpasses were also used by elk Cervus canadensis (1,953 crossings), pronghorns Antilocapra americana (201), coyotes Canus latrans 170, bobcats Lynx rufus (77), badgers Taxidea taxus 171, moose Alces alces 172, raccoons Procyon lotor 173and cougars Puma concolor 174. Seven concrete underpasses (approximately 6 m wide, 3 m high and 18 m long) and 21 km of fencing were installed in 2001–2008. Three camera traps/underpass were operated from 1 October (16 December in first year) to 31 May between 2008–2009 and 2010–2011. Vehicle-deer collision data were collated before (1 January 1990–1 October 2001) and after underpass construction (1 October 2008–1 May 2011).

  • 175 Sawaya M.A., Clevenger A.P. & Kalinowski, S.T. (2013) Demographic connectivity for ursid population (...)

232A study in 2006–2008 of 18 wildlife crossings under a highway, along with roadside fencing, in a national park in Alberta, Canada175 found that American black bears Ursus americanus and grizzly bears Ursus arctos used underpasses. Over three years, 218 crossings of American black bears and 153 of grizzly bears were detected. These were through 13 culverts (black bear: 44 crossings; grizzly bear: 36) and five open-span underpasses (black bear: 174 crossings; grizzly bear: 117). Bear crossings were monitored at 20 of 25 wildlife crossing structures in Bow Valley, Banff National Park, including 18 culverts and underpasses. Fencing (2.4 m high) was installed alongside the road. Bear tracks were counted in May–October 2006, April–October 2007 and April–October 2008 on track pads, comprising 1.5–2 m of sandy loam, spanning the width of the wildlife crossing. Track pads were checked every two days and the species, direction of travel and number of animals was recorded.

  • 176 Alonso, R. S., Lyren, L. M., Boydston, E. E., Haas, C.D., & Crooks, K.R. (2014) Evaluation of road (...)

233A study in 1997–2009 along a major road in California, USA176 found that all 19 culverts under the road (most of which were in areas with roadside fencing) were used as road crossing points by coyotes Canis latrans, bobcats Lynx rufus, and mule deer Odocoileus hemionus. Coyotes used 18–19 of the 19 culverts studied, and bobcats used 13–19 culverts. Mule deer used 1–4 of the five underpasses considered suitable for them. Ranges represent the numbers of culverts used in each of two survey periods. Sixteen culverts were part of a road upgrade programme, conducted in 2005, that included installation of 3-m-high roadside fencing. From November 1997 to January 2000, remotely triggered cameras were placed in each culvert. Cameras were again placed in each culvert from August 2008 to September 2009. Between the two surveys, the road network was expanded and adjacent habitat was restored.

  • 177 Bond A.R. & Jones D.N. (2014) Roads and macropods: interactions and implications. Australian Mammal (...)

234A review published in 2014 of eleven studies in Australia177 found that underpasses, separated from roads by fencing, were used by red-necked wallabies Macropus rufogriseus, swamp wallabies Wallabia bicolor, red-legged pademelons Thylogale stigmatica, long-nosed potoroos Potorous tridactylus and Lumholtz’s tree-kangaroos Dendrolagus lumholtzi. At all road underpasses, fencing was used to deter animals crossing roads rather than using underpasses. Underpasses in the study were 1.2–3.4 m high, 2.4–3.7 m wide, and 20–52 m long.

  • 178 Taylor B.D. & Goldingay R.L. (2014) Use of highway underpasses by bandicoots over a 7-year period t (...)

235A before-and-after study in 2000–2008 along a highway through swamp and woodland in New South Wales, Australia178 found that after being extended, underpasses beneath a newly constructed carriageway (in areas with roadside fencing), were used less by northern brown bandicoots Isoodon macrourus and long-nosed bandicoots Perameles nasuta. Bandicoot crossings through underpasses averaged 0.03/day after underpass extension, compared to 0.5/day during road widening and 1.1/day before widening. Construction of a single-carriageway by-pass finished in 1998. Six underpasses, 90–240 m apart, along 750 m of bypass, were studied. Underpasses were 2.4 m wide, 1.2 m high and 17–19 m long. In 2005–2006, an additional highway carriageway was constructed, with a 20–30-m-wide vegetated central strip. Four underpasses were extended, with an above-ground, enclosed section across the central strip, one underpass ran continuously under both carriageways and one linked with a creek bridge under the new carriageway. Crossings were 49–58 m long. Crossing entrances were separated from the road by 1.8-m-high fencing. Footprint sand pads were checked daily over 4–8 days to document tunnel passages. Underpasses were surveyed five times before widening (spring 2000 to autumn 2005), four times during widening (spring 2005 to spring 2006) and four times after widening (summer 2007 to autumn 2008). Not all underpasses were surveyed each time.

  • 179 Chambers B. & Bencini R. (2015) Factors affecting the use of fauna underpasses by bandicoots and bo (...)

236A study in 2012–2013 in six urban sites in Western Australia, Australia179 found that underpasses, separated from roads by fencing, were used by mammals to cross the road. Southern brown bandicoots Isoodon obesulus fusciventer crossed 540 times, western grey kangaroos Macropus fuliginosus crossed 186 times and brushtail possums Trichosurus vulpecula crossed twice. Underpasses were also used by several invasive mammal species. Road crossings were monitored through 10 underpasses from May 2012 to May 2013, using camera traps. Underpasses were round (0.6–0.9 m diameter) or square culverts (0.6–1.2 m wide, 0.5–1.2 m high). They were 23–88 m long and separated from roads by 0.6–1.8-m-high fences. The time since construction ranged from two to 19 years.

  • 180 Murphy-Mariscal M.L., Barrows C.W. & Allen M.F. (2015) Native wildlife use of highway underpasses i (...)

237A study in 2010–2012 of a desert region of California, USA180 found that underpasses in areas with roadside fencing were used by a range of native mammals. There were 3,778 wildlife occurrences (mammals and birds) recorded over 4,279 monitoring days (where a monitoring day is one underpass monitored for one day). Rodents made up 32 % of occurrences. Rabbits and hares, mainly desert cottontails Sylvilagus audubonii, made up 29 %. Birds made up 27 % of wildlife occurrences. Other mammals recorded included mule deer Odocoileus hemionus, mountain lion Puma concolor, bobcat Lynx rufus, coyote Canis latrans and ground squirrels (frequencies not reported). Seven underpasses, measuring 18–150 m wide, 3–9 m high and 12–112 m long, were studied. Roads were fenced, but gaps allowed animal passage and fences did not funnel animals towards underpasses. Wildlife movements were monitored from July 2010 to November 2012, using camera traps and track pads.

  • 181 Huijser M.P., Fairbank E.R., Camel-Means W., Graham J., Watson V., Basting P. & Becker D. (2016) Ef (...)

238A replicated, site comparison study in 2013 along a highway in Montana, USA181 found that underpasses connected with long roadside fences were used by similar numbers of large mammals compared to those with no fences or very short fences. The rate of large mammal crossings through underpasses connected to 6.1–6.2-km-long roadside fences (0.44 mammals/underpass/day) and 1.4–2.7-km-long fences (0.77 mammals/underpass/day) was not significantly different to the rate crossing through underpasses with no fencing or with fences up to 0.4 km long (0.22 mammals/underpass/day). Mammals identified using underpasses were white-tailed deer Odocoileus virginianus, mule deer Odocoileus hemionus, American black bear Ursus americanus, mountain lion Puma concolor, grizzly bear Ursus arctos and elk Cervus canadensis. Twenty-three underpasses were monitored along US Hwy 93 North. Roads were fenced alongside underpasses for 0.0–6.2 km length with 2.4-m high fencing. Wildlife crossings were monitored using ≥1 camera trap/underpass in January–December 2013.

  • 182 Huijser M.P., Fairbank E.R., Camel-Means W., Graham J., Watson V., Basting P. & Becker D. (2016) Ef (...)

239A study in 2012–2013 along a highway in Montana, USA182 found that underpasses in areas with roadside fencing were used by white-tailed deer Odocoileus virginianus for crossing the road more often than was the road surface. This result was not tested for statistical significance. There were 727 road crossings with 721 by white-tailed deer, three by American black bear Ursus americanus and three by either this species or grizzly bear Ursus arctos. Eighty-two percent of all crossings were through underpasses and 18 % were above the road. Ten fenced underpasses were monitored along US Hwy 93 North. Underpasses were 2–5 m high and 4–40 m wide. Fences were 2.4 m high and 3–256 m long. The proportion of wildlife crossings did not change with fence length (data presented as regression results). Between June 2012 and October 2013, road crossings were monitored for two weeks/ underpass using one camera trap at each fence end and at least one at an underpass entrance. Only highway crossings in which animals entered or exited underpasses or accessed or left the highway at a fence end (not returning within ≤3 minutes) were considered.

  • 183 Simpson N.O., Stewart K.M., Schroeder C., Cox M., Huebner K. & Wasley, T. (2016) Overpasses and und (...)

240A study in 2010–2014 of two sites along a highway in Nevada, USA183 found that underpasses, in areas with roadside fencing, were used by migratory mule deer Odocoileus hemionus to cross a road, but less so than were overpasses. Fewer mule deer crossed the road through three underpasses (44–629 deer crossings/underpass/season) than across two overpasses (234–4,007 deer crossings/overpass/season). Crossing structures, 1.5–2.0 km apart, at important crossings for migratory deer, were completed by August 2010 (August 2011 for one overpass). One site had two underpasses and one overpass. The other had one of each structure. Underpasses, 8 m wide, 28 m long and 6 m tall, were oval in cross-section. Concrete arch overpasses, were 31–49 m wide and 8–20 m long. All structures had soil bases. Fencing, 2.4 m high, deterred deer access to the highway between crossings and extended 0.8–1.6 km beyond crossings at each site. Crossings were monitored during eight mule deer migratory periods (autumn 2010 to spring 2014), using camera traps, over 10 weeks in each migration (15 September to 1 December and 1 March to 15 May). Cameras were positioned 12 m apart along crossing structures.

  • 184 Ford A.T., Barrueto M. & Clevenger A.P. (2017) Road mitigation is a demographic filter for grizzly (...)

241A study in 1996–2014 of a major highway in Alberta, Canada184 found that culverts, in areas with roadside fencing, were used as crossing points by grizzly bears Ursus arctos, but less often than were overpasses, especially by family groups. Over 18 years, grizzly bears used culverts less often (122 crossings/structure) than they used overpasses (241 crossings/structure). Over eight years, bear family groups used culverts less often (0.0–0.3 family groups/year/structure) than they used overpasses (1.4 family groups/year/structure). In 1996–2006, 2-m-wide pads, were covered in sandy-loam soil to survey bear movements at 23 crossing structures. From 2008 to 2014, remote cameras were installed at all crossing structures. As more crossing structures were built in the area, they were added to the survey, up to a maximum of 19 culverts and 18 overpasses. Crossing structure entrances were separated from the road by fencing.

5.13. Install barrier fencing along railways

242https://www.conservationevidence.com/​actions/​2590

243One study evaluated the effects on mammals of installing barrier fencing along railways. This study was in Norway1.

244COMMUNITY RESPONSE (0 STUDIES)

245POPULATION RESPONSE (1 STUDY)

246Survival (1 study): A before-and-after study in Norway1 found that fencing eliminated moose collisions with trains, except at the fence end.

247BEHAVIOUR (0 STUDIES)

Background
Collisions with trains can cause substantial numbers of mammal deaths (e.g. Gundersen & Andreassen 1998). Barrier fencing alongside railways may reduce access to railway tracks by mammals and, thus, reduce the number of mammal-train collisions.

248Gundersen H. & Andreassen H.P. (1998) The risk of moose Alces alces collision: A predictive logistic model for moose-train accidents. Wildlife Biology, 4, 103–110.

  • 185 Andreassen H.P., Gundersen H. & Storaas T. (2005) The effect of scent-marking, forest clearing, and (...)

249A before-and-after study in 1985–2003 in forest in southern Norway185 found that 1 km of fencing eliminated moose Alces alces collisions with trains along that stretch. The exception was one killed at the fence end. Within the wider study area, there were 0.58 moose/km killed each winter during the study period. In 1995, a 1-km-long wire-mesh fence was erected alongside a railway line. Moose-train collisions along a 100- km stretch of the railway line were recorded from July 1985–April 2003.

5.14. Install wildlife warning reflectors along roads

250https://www.conservationevidence.com/​actions/​2591

251Fifteen studies evaluated the effects on mammals of installing wildlife warning reflectors along roads. Nine studies were in the USA1–5,7,9,10,11, three were in Austalia8,12,13, two were in Germany14,15 and one was in Denmark6.

252COMMUNITY RESPONSE (0 STUDIES)

253POPULATION RESPONSE (10 STUDIES)

254Abundance (1 study): A before-and-after study in Australia8 found that, when warning reflectors were installed (along with speed restrictions, reflective wildlife signs, rumble strips, wildlife escape ramps and an educational pamphlet), a small population of eastern quoll re-established in the area.

255Survival (10 studies): Five of eight controlled or before-and-after studies in the USA1,3,4,5,7,9,10 and Germany15 found that wildlife warning reflectors did not reduce collisions between vehicles and deer3,4,9,10,15. Two studies found that vehicle-deer collisions were reduced by reflectors1,7 and one found that collisions were reduced in rural areas but increased in suburban areas5. A before-and-after study in Australia8 found that, when warning reflectors were installed (along with speed restrictions, reflective wildlife signs, rumble strips, wildlife escape ramps and an educational pamphlet), vehicle collisions with Tasmanian devils, but not eastern quolls, decreased. A review of two studies in Australia13 found mixed responses of mammal road deaths to wildlife warning reflectors.

256BEHAVIOUR (5 STUDIES)

257Behaviour change (5 studies): Three of four studies (including three controlled studies), in the USA2,11, Denmark6 and Germany14, found that wildlife warning reflectors did not cause deer to behave in ways that made collisions with vehicles less likely (such as by avoiding crossing roads). The other study found that deer initially responded to wildlife reflectors with alarm and flight but then became habituated6. A replicated, controlled study in Australia12 found that one of four reflector model/colour combinations increased fleeing behaviour of bush wallabies when lights approached. The other combinations had no effect and none of the combinations affected red kangaroos.

Background
Reflectors are installed on posts along the edge of the road, a certain distance apart and at the height of the average vehicle headlamp. At night, as vehicle lights approach, the reflectors glow brighter and create an ‘optical fence’ as light from headlights is reflected onto roadside habitat, which aims to deter wildlife from approaching the road until the vehicle has passed. Polished stainless-steel wildlife mirrors can also be installed to reflect the headlights from passing cars causing light to flicker sharp, pencil-like beams that aim to startle animals and stop them moving until the lights have passed.

  • 186 Schafer J.A. & Penland S.T. (1985) Effectiveness of Swareflex reflectors in reducing deer-vehicle a (...)

258A replicated, controlled study in 1981–1984 in a forest-grassland area in Washington, USA186 found that wildlife reflectors reduced road deaths of deer Odocoileus sp. Fewer deer were killed when reflectors were uncovered (6 of the 58 killed overall) compared to when they were covered (52 of the 58 road-kills recorded). Four test sections were established along a highway (0.7–1.1 km long). Swareflex wildlife reflectors (17 × 5 cm; red) were mounted on 1-m posts, 20 m apart (10 m at bends) and 1 m from the edge of the highway. Reflectors in each section were alternately covered and uncovered at 1-week intervals during October–April from February 1981–April 1984. Intervals were extended to two weeks after December 1982. Alternate test sections were paired so that reflectors in each pair were covered while reflectors in adjacent sections were uncovered. Road-kills were recorded daily.

  • 187 Zacks J.L. (1986) Do white-tailed deer avoid red? An evaluation of the premise underlying the desig (...)

259A controlled study in 1984 of captive deer in Michigan, USA187 found that reflectors, angled to deflect car headlight illumination into adjacent habitat, did not affect crossing rates of white-tailed deer Odocoileus virginianus. There were no significant differences in crossing rates when the route was fitted with red reflectors (256 crossings), white reflectors (200 crossings) or no reflectors (264 crossings). Ten captive-born deer were housed in a 3.5-acre pen. Five posts were installed in a line at 66-foot intervals. A pair of car headlights was aimed alongside this line. Each night, one trial each was run using no reflectors, white reflectors and red reflectors. Reflectors were fastened 42 inches up posts. All treatment orders were replicated three times. Data were collected over 18 nights, between 20 August and 6 October 1984. Trials lasted 15 minutes. Water (to attract deer) was dispensed noisily, by remote control, at five and 10 minutes, first on one side of the post line, then the other. Water ran into containers with holes, which drained in 1.5 minutes. Crossings by deer were counted by observers in concealed positions.

  • 188 Waring G.H., Griffis J.L. & Vaughn M.E. (1991) White-tailed deer roadside behavior, wildlife warnin (...)

260A before-and-after study in 1977–1982 along a road through agricultural land in Illinois, USA188 found that warning reflectors did not reduce deer-vehicle collisions. A similar number of white-tailed deer Odocoileus virginianus was killed overnight during a year with reflectors installed (six deer) as during the previous two years before reflectors were installed (5–6/year). The local deer population was reported to have decreased over this time. Behaviour of deer crossing the road or feeding at the roadside did not appear to be altered by reflectors. Eighty Swareflex wildlife warning reflectors were installed along each side of a 0.8-km section of a two-lane highway (speed limit 88 km/hour). Reflectors comprised two mirrors (5 × 17 cm) covered with red prism plates on posts 20 m apart, 3 m from the road edge. Collision data were provided by transportation personnel and direct observations.

  • 189 Reeve A.F. & Anderson S.H. (1993) Ineffectiveness of Swareflex reflectors at reducing deer vehicle (...)

261A controlled study in 1986–1989 along a highway in Wyoming, USA189 found that Swareflex reflectors did not reduce road deaths of mule deer Odocoileus hemionus. More deer were killed when reflectors were displayed (126) than when they were covered (64). During the same periods, there were 85 and 62 deer killed respectively in a control site without reflectors. After three years, only 215 (61 %) of the reflectors were still in good condition. In October 1986, Swareflex reflectors were installed on both sides of a 3.2-km section of a highway (US 30). The 350 reflectors were on posts (height 61–91 cm), 20 m apart (10 m on bends) and 3 m from the road edge. Reflectors were covered and uncovered at 1-week intervals from October 1986 to February 1987 and then at 2-week intervals until May 1989. A control section (3.2 km) without reflectors was also monitored. Deer-vehicle collisions were monitored in October 1986–April 1987 (daily), November 1987–April 1988 and October 1988– May 1989 (each at 2–5-day intervals).

  • 190 Pafko F. & Kovach B. (1996) Experience with deer reflectors. Proceedings of the Trends in addressin (...)

262A replicated, before-and-after study in 1980–1994 along 16 highways in Minnesota, USA190 found that reflectors reduced rural deer-vehicle collisions by 50–97 %, but that collisions in suburban areas increased. Collisions were reduced by 90 % along roads in the four coniferous forest areas (after installation: 2 collisions; before: 26), 79 % along roads in the four ‘farmland’ areas (after installation: 9 collisions; before: 54) and 87 % along roads in the four hardwood forest areas (after installation: 3 collisions; before: 25). However, collisions increased in four suburban areas (after installation: 4.4–7.3 collisions/year; before: 2.4–3.4). Swareflex brand red reflectors were installed along 16 highway sections through three different rural habitats and in a suburban area. Deer-vehicle collisions were monitored before (pre-1988) and after installation (1988–1994).

  • 191 Ujvári M., Baagøe H.J. & Madsen A.B. (1998) Effectiveness of wildlife warning reflectors in reducin (...)

263A study in 1996 in a forest in Zealand, Denmark191 found that fallow deer Dama dama initially responded to wildlife reflectors with alarm and flight but became habituated to the light reflection. On the first night, using a low level of lighting, deer fled from the reflection in 99 % of cases. On night five, using the same light level, only 16 % fled and 74 % did not react. On nights 6–7 with four light levels, 86–94 % fled. However, on nights 16–17 only 30–37 % fled and 38–48 % showed no response. Following a one-night break, deer fled almost twice as much as they did the night before the break (35–90 % vs 20–54 %). Feeding deer were exposed to light reflections (WEGU reflector; two sloping mirrors within a cover) at predetermined time intervals and their behavioural responses were recorded. Data were collected over 17 nights (two with no lighting used) in April 1996. Only the lowest light level was used on the first five nights. Subsequently, four levels were used.

  • 192 Gulen S., McCabe G. & Wolfe S.E. (2000) Evaluation of wildlife reflectors in reducing vehicle-deer (...)

264A replicated, randomized, controlled study in 1999–2005 along a highway in Indiana, USA192 found that wildlife reflectors reduced deer-vehicle collisions by 19 % overall, but there was no difference between different reflector colours, spacing or design. When reflector sites were combined and compared with sites without reflectors, there was a 19 % reduction in deer-vehicle collisions with reflector use. However, there was no significant difference in numbers of collisions between different reflector combinations (colours, spacing, single/dual design, reflectors on central reservation or not) or between each reflector combination and sites without reflectors. The greatest decrease in collisions was associated with 30-m reflector spacing regardless of colour or design. In 1999, two replicates of 16 treatment combinations (randomized order) were installed along two 1.6-km-long road sections. Treatments were different reflector colour (red and blue/green), spacing (30 m and 45 m), design (single and dual reflectors) and whether or not the central reservation also had reflectors. There was a 1.6-km control section without reflectors at each end of each replicate. Numbers of deer-vehicle collisions were recorded in April–May and October–November in 1999–2005.

  • 193 Jones M.E. (2000) Road upgrade, road mortality and remedial measures: impacts on a population of ea (...)

265A before-and-after study in 1990–1998 in Tasmania, Australia193 found that, following installation of wildlife warning reflectors, speed restrictions, reflective wildlife signs, rumble strips, wildlife escape ramps and publication of an educational pamphlet, an eastern quoll Dasyurus viverrinus population partially re-established and vehicle collisions with Tasmanian devils Sarcophilus laniarius, but not eastern quolls, decreased. Effects of the different actions were not investigated individually and results were not tested for statistical significance. Following local extinctions, 3–4 quolls re-colonised within six months of installation, increasing to ≥8 animals after two years. Road-kills for quolls were similar after implementation (1.5/year) compared to before (1.6/ year), but decreased for Tasmanian devils (after: 1.5/year; before: 3.6). Following road widening in 1991, vehicle-wildlife collisions increased and quolls became locally extinct (from 19 animals). In 1996, reflective wildlife deterrents (Swareflex; 20 m intervals, 50 cm above ground) were installed, along with the other five interventions. Animals were surveyed using 60 cage traps for three nights during alternate months in October 1990–April 1993. Then, 10–20 traps were set for 20–100 trap nights in April, May and July 1995–1998. Spotlight counts were made once or twice in 1991, 1995, 1996 and 1998. Road-kills were recorded in 1990–1996.

  • 194 Cottrell B.H. (2003) Technical assistance report: evaluation of deer warning reflectors in Virginia(...)

266A replicated, controlled study in 2000–2003 along 10 highways in Virginia, USA194 found that warning reflectors did not reduce collisions between vehicles and deer Odocoileus sp. There was a similar rate of deer road casualties on sections with reflectors (4.6/mile/year) compared to sections without reflectors (4.8/mile/year). Deer warning reflectors (red) were installed on posts along 0.4–2.3-km sections of 10 highways (2–4 lane) from October 2000 to May 2002. Reflector sites and adjacent sites without reflectors were each monitored for 6–28 months. Deer road-kills data were collated by officials from the state Department of Transportation.

  • 195 Rogers E. (2004) An ecological landscape study of deer vehicle collisions in Kent County, Michigan. (...)

267A replicated, controlled, before-and-after study in 1992–2000 along roads in Michigan, USA195 found that wildlife warning reflectors did not reduce deer-vehicle collisions. The rate of collisions after reflectors were installed (8.5/year) was similar to that before reflectors were installed (8.2/year). This was also similar to the collision rate on another road section, at the same time, where reflectors were not installed (after: 13/year; before: 9.5/year). The total number of deer-vehicle collisions recorded was 279. In 1998, Swareflex wildlife warning reflectors were installed along three 3.2-km-long sections of road. Three additional 3.2-km-long road sections were controls with no reflectors. Collisions between 18: 00 and 24: 00 h, monitored by Michigan State Police, were compared before (1992–1997) and after (1998 and 2000) reflector installation.

  • 196 D’Angelo G.J., D’Angelo J.G., Gallagher G.R., Osborn D.A., Miller K.V. & Warren R.J. (2006) Evaluat (...)

268A before-and-after study in 2004–2005 at a college campus in Georgia, USA196 found that wildlife warning reflectors did not reduce white-tailed deer Odocoileus virginianus behaviours that were likely to cause collisions with vehicle. When red or blue-green reflectors were installed, there was a proportional increase in behaviours that were likely to cause deer–vehicle collisions. White or amber reflectors resulted in an increased rate both of responses that increase and that decrease collision likelihood. A total of 1,370 deer responses were recorded. A smaller proportion of animals stopped moving toward the road as a vehicle approached when reflectors were installed (red: 13 %; white: 55 %; blue-green: 14 %; amber: 50 %) compared to before reflectors were installed (64 %). In two test areas (5 km apart), 15 posts were installed 15 m apart, staggered on opposite sides of the road. After two weeks, Strieter-Lite Wild Animal Highway Warning Reflectors were installed on posts (61–76 cm above road). Deer–vehicle interactions were observed using an infrared camera for four hours/night before (15 nights in November 2004–January 2005) and after installation of reflectors (January–May 2005). Two reflector colours were tested in each area for 15 nights each.

  • 197 Ramp D. & Croft D.B. (2006) Do wildlife warning reflectors elicit aversion in captive macropods? Wi (...)

269A replicated, controlled study in 2006 at two grassland sites in New South Wales, Australia197 found that red Swareflex wildlife warning reflectors increased the proportion of bush wallabies Macropus rufogriseus fleeing approaching lights but red Strieter-Lite reflectors and white version of both types did not affect proportions of fleeing bush wallabies or red kangaroos Macropus rufus. A higher proportion of bush wallabies fled when lights shone at red Swareflex reflectors (8 %) than when lights shone without reflectors (3 %). There was no such response for red kangaroos (reflectors: 3 %; no reflectors: 5 %). There were no significant differences in fleeing response rates for bush wallabies when lights shone at red Strieter-Lite reflectors (with: 5 %; without: 3 %) or at white reflectors of either type (with: 5–6 %; without: 3 %). There were also no significant differences in fleeing response rates for red kangaroos when lights shone at red Strieter-Lite reflectors (with: 5 %; without: 7 %) or at white reflectors of either type (with: 3–5 %; without: 5 %). In two grassland enclosures, a ‘road’ strip was mown and had 55-W lights installed in pairs every 20 m. Sequentially activating these lights mimicked approaching cars. Wildlife warning reflectors (Swareflex and Strieter-Lite) were placed on either side of the road at 20-m intervals. Over three days, animals were exposed to one night with no lights, one night with lights and no reflectors and one night with lights and reflectors. This three-day sequence was repeated 15 times and fleeing behaviour was surveyed using infrared cameras.

  • 198 Bond A.R. & Jones D.N. (2014) Roads and macropods: interactions and implications. Australian Mammal (...)

270A review of two studies in 2000–2010 in Australia198 found that installing wildlife warning reflectors had mixed results regarding reducing road deaths of mammals. One study showed reflectors prompted increased vigilance and flight by red kangaroos Macropus rufus. Another study showed that reflectors did not reduce the number of Proserpine rock wallabies Petrogale persephone killed by collisions with vehicles.

  • 199 Brieger F., Hagen R., Kröschel M., Hartig F., Petersen I., Ortmann S. & Suchant, R. (2017) Do roe d (...)

271A replicated, randomized, controlled study in 2002–2014 in two grassland sites and five roadside areas in Germany199 found that wildlife warning reflectors along roads did not cause roe deer Capreolus capreolus to evade traffic more effectively. In two fenced grassland areas, there was no significant difference in successful evasion of traffic when wildlife reflectors were used and not used (data reported as model results). The same results were found in five roadside areas (data reported as model results). In two fenced grassland areas, reflectors and headlights (mimicking cars), headlights without reflectors and no reflectors or headlights were each in place for two periods of one week each. This was carried out four times between September 2012 and April 2014. The order of these combinations of reflectors and lights was varied randomly. Groups of three to six deer occupied each area. Their behaviour was monitored by infrared video cameras. At five sites, three thermal cameras were installed between June 2012 and June 2014 in trees close to roads at 3–4 m high. Between July 2012 and April 2014, wildlife warning reflectors were installed along both side of the roads. The behaviour of roe deer clearly visible in video recordings was documented.

  • 200 Benten A., Hothorn T., Vor T. & Ammer C. (2018) Wildlife warning reflectors do not mitigate wildlif (...)

272A replicated, controlled study in 2014–2017 of 151 road sites in central Germany200 found that four types of wildlife warning reflector did not reduce wildlife-vehicle collisions. The number of vehicle collisions was similar with and without four types of wildlife warning reflectors for three groups of mammals: deer (roe deer Capreolus capreolus, red deer Cervus elaphus, fallow deer Dama dama); wild boar Sus scrofa; and other mammals (badger Meles meles, red fox Vulpes vulpes, hare Lepus europaeus/rabbit Oryctolagus cuniculus, wildcat Felis silvestris, racoon Procyon lotor). Data are reported as statistical model results. Three types of wildlife warning reflectors were installed along 151 stretches of road (average 2 km long): dark-blue reflectors (51 sites); light-blue reflectors (50 sites) and multi-coloured reflectors (50 sites). In addition, one type of reflector (transparent/silver) with an acoustic warning (1.5 second sounds triggered by vehicle headlights) was installed along a 200 m stretch of road at 10 of the 101 sites with blue reflectors. Reflectors were installed on posts (55–100 cm high) spaced 25–50 m apart. Wildlife-vehicle collisions reported to the police (1,984 in total) were analysed for 12 months with the reflectors installed and 12 months without in 2014–2017.

5.15. Install acoustic wildlife warnings along roads

273https://www.conservationevidence.com/​actions/​2592

274Two studies evaluated the effects on mammals of installing acoustic wildlife warnings along roads. One study was in Demark1 and one was in Australia2.

275COMMUNITY RESPONSE (0 STUDIES)

276POPULATION RESPONSE (0 STUDIES)

277BEHAVIOUR (2 STUDIES)

278Behaviour change (2 studies): A before-and-after study in Denmark1 found that sound from acoustic road markings did not alter fallow deer behaviour. A controlled study in Australia2 found that Roo-Guard® sound emitters did not deter tammar wallabies from food and so were not considered suitable for keeping them off roads.

Background
Collisions with vehicles can be a major cause of mortality for wild mammals and, especially where larger mammal species are involved, a cause of injury, death and economic loss for motorists (Conover
et al. 1995). A range of interventions may be employed to deter mammals for accessing roads. This can include use of acoustic warnings which can either be devices that emit sounds or modifications to the road surface that produce noise when vehicle tyres pass over them.
See also:
Fit vehicles with ultrasonic warning devices.

279Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

  • 201 Ujvári M., Baagøe H.J. & Madsen A.B. (2004) Effectiveness of acoustic road markings in reducing dee (...)

280A before-and-after study in 1997 in a mixed hardwood forest in Zealand, Denmark201 found that acoustic road markings did not alter the behaviour of fallow deer Dama dama. Behavioural responses varied among nights, but deer showed increasing indifference to sounds from road markings over 11 nights (i.e. deer appeared to become habituated). Behaviour differed before (flight: 2 %, no reaction: 96–99 %) and during playbacks, but deer reactions declined over 10 nights of playbacks (night 1: flight 13 %; nights 8–10: flight 3–0 %, no reaction 88–99 %). An area of forest next to an unpaved road closed to vehicles was selected where a herd of 6–12 fallow deer were fed (maize). Recordings of a car passing two types of acoustic road markings which produced sounds when a vehicle’s tyres passed over (low frequency longflex; higher spossflex), multiplied to 70 sequences (each 0.11–0.16 s) were made. Behavioural responses of deer to play-back sounds (58 decibels) at predetermined time intervals (exposure for: 5, 2, 7, 3, 1 and 2 minutes) were monitored over 11 nights in February–March 1997. Behaviour was also recorded every 15 minutes during the two nights before sound trials commenced.

  • 202 Muirhead S., Blache D., Wykes B. & Bencini R. (2006) Roo-Guard® sound emitters are not effective at (...)

281A controlled study in 2005 in a grass enclosure in Western Australia, Australia202 found that Roo-Guard® sound emitters did not deter tammar wallabies Macropus eugenii from food and so were not considered suitable for keeping them off roads. There was no significant difference between the use of the enclosure or food sources when the Roo-Guards were switched on or off. This was the case even when there was an alternative source of food available away from Roo-Guards. The device did not result in any obvious behavioural responses such as flight or distress. Nine tammars were kept in an enclosure (60 × 30 m), with a test area (60 × 20 m) divided into 12 squares. The remainder of the enclosure was covered in trees and bushes. Roo-Guard® Mk II high-frequency sound emitters were installed on the edge of the test area, 0.5 m off the ground. Animals were observed though a night-vision scope on three nights (18: 00–21: 00 h) with the Roo-Guard® turned on and three with it turned off, for each of four treatments: food 20 m from Roo-Guard®, or food 20 and 60 m from Roo-Guard®, and the same two treatments but with the sides with food and Roo-Guards swapped over.

5.16. Install wildlife crosswalks

282https://www.conservationevidence.com/​actions/​2593

283One study evaluated the effects on mammals of installing wildlife crosswalks. This study was in the USA1.

284COMMUNITY RESPONSE (0 STUDIES)

285POPULATION RESPONSE (1 STUDY)

286Survival (1 study): A replicated, before-and-after, site comparison study in the USA1 found that designated crossing points with barrier fencing did not significantly reduce road deaths of mule deer.

287BEHAVIOUR (0 STUDIES)

Background
Crosswalks are intended to guide wildlife across roads at specific crossing points along fenced stretches of highway and to provide drivers with warning signs indicating specific locations where animals are expected to cross. In this narrow crossing zone, animals walking on to the road are guided directly across the road by river cobbles and/or painted cattle guards.

  • 203 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing dee (...)

288A replicated, before-and-after, site comparison study in 1991–1995 along two highways in Utah, USA203 found that designated crossing points with barrier fencing did not significantly reduce road deaths of mule deer Odocoileus hemionus. Deaths decreased on both fenced and unfenced sections but the rate of decline was not significantly higher on fenced road sections with crossings (after: 36–46 deer fatalities over 15 months; before: 111–148 over 36 months) than over the same period on unfenced sections (after: 34–63; before: 75–123). In September 1994, four and five crossing points were installed along a two-and a four-lane highway respectively. Fencing (2.3 m high) restricted access to roadside resources and directed deer to crossing points. At these points, deer could jump a 1-m-high fence into funnel shaped fencing (2.3 m high) with a narrow opening to the road. One-way gates allowed deer trapped along the road to escape. Three warning signs, 152 m apart before crossings, and painted lines across the road at crossings, indicated to drivers that it was a crossing point. Road deaths were monitored weekly along treatment and nearby control roads before and after crossing installation, from October 1991 to November 1995.

5.17. Install wildlife exclusion grates/cattle grids

289https://www.conservationevidence.com/​actions/​2594

290Three studies evaluated the effects on mammals of installing wildlife exclusion grates or cattle grids. All three studies were in the USA1,2,3.

291COMMUNITY RESPONSE (0 STUDIES)

292POPULATION RESPONSE (0 STUDIES)

293BEHAVIOUR (3 STUDIES)

294Behaviour change (3 studies): Two of three studies (including two replicated, before-and-after studies), in the USA1,2,3, found that steel grates largely prevented crossings by deer2,3 whilst two found that they did not prevent crossings by deer and elk1 or black bears3. In one of the studies, only one of three designs prevented crossings2.

Background
Wildlife exclusion grates or cattle grids are designed to discourage wildlife, particularly ungulates, from walking through a gap in a fence where an access road approaches a larger road with higher traffic volume and vehicle speeds for example. If effective, they could reduce animal mortality and also collision-related risks for motorists.
See also:
Agriculture & Aquaculture -Install metal grids at field entrances to prevent mammals entering to reduce human-wildlife conflict.

  • 204 Reed D.F., Pojar T.M. & Woodard T.N. (1974) Mule deer responses to deer guards. Journal of Range Ma (...)

295A study in 1972–1973 of two fences in Colorado, USA204 found that steel rail deer guards did not prevent crossings through vehicle openings by mule deer Odocoileus hemionus hemionus or elk Cervus canadensis. In test conditions, 16 of 18 mule deer released adjacent to 12, 18 or 24-foot-wide guards, crossed the guards, in an average time of 173 s. During natural encounters, 11 mule deer and one elk crossed a 24-ft-long guard and four mule deer crossed a 12-ft-long guard. There were at least 11 approaches by mule deer and three by elk in which animals did not then cross. Guards, at vehicle openings in 8-foot-high fences, comprised flat steel rails, 0.5 inches wide, 4 inches high and 120 inches long, set 4 inches apart. Rails were perpendicular to the traffic direction. Eighteen deer were released in situations where crossing guards provided the only exit. Deer and elk tracks, from natural encounters with two guards, were examined periodically, from 29 June 1972 to 19 April 1973.

  • 205 Peterson M.N., Lopez R.P., Silvy N.J., Owen C.B., Frank P.A. & Braden A.W. (2003) Evaluation of dee (...)

296A replicated, before-and-after study in 2001 in Florida, USA205 found that one of three deer exclusion grates excluded Florida Key deer Odocoileus virginianus clavium. Only one deer crossed the grate that incorporated diagonal cross-members into the metal grid, compared to 305 that crossed when the grate was covered over with plywood. Fifty deer crossed the two grate designs without diagonal cross-members, compared to 199 that crossed when covered over. Males were more successful at crossing than females. In 2001, three types of grate were tested for deer-exclusion efficiency. All grates were 6.1 × 6.1 m, each with a different grate pattern: grid of 10 × 13 cm rectangles with diagonal cross member through each rectangle and 8 × 10 cm or 10 × 8 cm rectangles without diagonal cross member. Food was provided within a fenced area accessible only by crossing the grate. Grates were covered (therefore, easily crossable) for 1–2 weeks and then uncovered for one week, three times (for two designs) or once (third design). Infrared cameras were used to monitor deer crossings.

  • 206 Allen T.D., Huijser M.P. & Willey D.W. (2013) Effectiveness of wildlife guards at access roads. Wil (...)

297A replicated, before-and-after study in 2003–2010 at two roadside areas in Montana, USA206 found that wildlife exclusion grates reduced crossings of a major highway by deer Odocoileus spp., but not by black bears Ursus americanus. After installing wildlife exclusion grates, a lower proportion of deer approaching the road subsequently crossed it (6 %) than did so before grates were installed (44 %). The proportion of black bears crossing the road, out of those approaching it, was not significantly different after grates were installed (62 %) compared to before they were installed (87 %). Between October 2004 and November 2010, fencing was installed along the roadside. Single exclusion grates were fitted at each of two junctions with minor roads. Grates were 6.8 m wide and 6.6 m long. In June–October of 2003–2005, eight 100 × 2 m areas were coated with sand to record animal tracks. Using these data, the percentage of animals that crossed the road was calculated. Wildlife cameras were placed at both grates between July 2008 and July 2010. The number of times an animal was ≤2 m from grates and whether it subsequently crossed were recorded.

5.18. Reduce legal speed limit

298https://www.conservationevidence.com/​actions/​2596

299One study evaluated the effects on mammals of reducing the legal speed limit. This study was in Canada1.

300COMMUNITY RESPONSE (0 STUDIES)

301POPULATION RESPONSE (1 STUDY)

302Survival (1 study): A controlled, before-and-after study in Canada1 found that speed limit reductions and enforcement did not reduce vehicle collisions with bighorn sheep or elk.

303BEHAVIOUR (0 STUDIES)

Background
High vehicle speed is generally considered to be a substantial contributing factor in wildlife-vehicle collisions. Speed limits can be reduced in areas where there are high numbers of collisions, either permanently or during seasonal migrations.

  • 207 Bertwistle J. (1999) The effects of reduced speed zones on reducing bighorn sheep and elk collision (...)

304A controlled, before-and-after study in 1983–1998 along a highway in Alberta, Canada207 found that speed limit reductions and enforcement did not reduce vehicle collisions with bighorn sheep Ovis canadensis or elk Cervus canadensis. Sheep collision rates were similar in the reduced speed zones after limits were reduced (10.4 collisions/year) compared to before (10.3/year). Concurrently, in control areas where the speed limit was not reduced, there were fewer collisions in this second period (2.5 collisions/year) than the first period (3.4/year). Elk collisions increased with the speed limit reduction (after: 9.6/year; before: 7.8/ year) but increased by more in the control zone (after: 14.3/year; before: 7.8/year). The local elk population increased 178 % during the study. In 1991, the speed limit along a rural two-lane highway was reduced from 90 km/h to 70 km/h on three road sections (2.5, 4.0 and 9.0 km long). Monitoring in 1995 indicated that <20 % of vehicles obeyed the 70 km/h limit. On average, 5,475 speeding tickets were issued/year. Animal-vehicle collisions were monitored for eight years before and eight years after speed limits were reduced, on three 2–3-km-long road sections for sheep and one 30-km-long section for elk. Vehicle speeds were monitored along two road sections in 1995.

5.19. Install traffic calming structures to reduce speeds

305https://www.conservationevidence.com/​actions/​2598

306One study evaluated the effects on mammals of installing traffic calming structures to reduce speeds. This study was in Australia1.

307COMMUNITY RESPONSE (0 STUDIES)

308POPULATION RESPONSE (1 STUDY)

309Abundance (1 study): A before-and-after study in Australia1 found that following installation of barriers to create a single lane, rumble strips, reflective wildlife signs, reflective wildlife deterrents, wildlife escape ramps and production of an educational pamphlet, a small population of eastern quoll population re-established in the area.

310Survival (1 study): A before-and-after study in Australia1 found that following installation of barriers to create a single lane, rumble strips, reflective wildlife signs, reflective wildlife deterrents, wildlife escape ramps and production of an educational pamphlet, vehicle collisions with Tasmanian devils, but not eastern quolls decreased.

311BEHAVIOUR (0 STUDIES)

Background
Reducing the design speed of a road can be used to reduce vehicle speed rather than reducing the legal speed limit. Traffic calming methods include speed bumps, rumble strips, curb or pavement extensions (to reduce road width) and raised central medians/ islands. Such structures get the attention of drivers and encourage them to slow down, which may help to reduce wildlife-vehicle collisions.

  • 208 Jones M.E. (2000) Road upgrade, road mortality and remedial measures: impacts on a population of ea (...)

312A before-and-after study in 1990–1998 in Tasmania, Australia208 found that following installation of barriers to create a single lane, rumble strips, reflective wildlife signs, reflective wildlife deterrents, wildlife escape ramps and publication of an educational pamphlet, an eastern quoll Dasyurus viverrinus population partially re-established and vehicle collisions with Tasmanian devils Sarcophilus laniarius, but not eastern quolls, decreased. Results were not tested for statistical significance. Following local extinction, 3–4 quolls re-colonised within six months of installation, increasing to ≥8 animals after two years. Road-kills were similar for quolls before and after implementation (1.6 vs 1.5/year), but decreased for Tasmanian devils (3.6 vs 1.5/year). Vehicle speeds declined by 20 km/h (17–35 % reduction) at the site centre and by 3–7 % at edges. Following road widening in 1991, vehicle-wildlife collisions increased and quolls became locally extinct (from 19 animals). In 1996, four ‘slow points’ (barriers, creating a single give-way lane, rumble strips and four other interventions) were created. Animals were surveyed using 60 cage traps for three nights in alternate months in October 1990–April 1993. Then, 10–20 traps were set for 20–100 trap nights in each April, May and July of 1995–1998. Spotlight counts were made once or twice in 1991, 1995, 1996 and 1998. Road-kills were recorded in 1990–1996. Vehicle speeds were recorded at four locations.

5.20. Modify vegetation along roads to reduce collisions with mammals by enhancing visibility for drivers

313https://www.conservationevidence.com/​actions/​2599

314• We found no studies that evaluated the effects of modifying vegetation along roads to reduce collisions with mammals by enhancing visibility for drivers.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Collisions with vehicles can be a major cause of mortality for wild mammals and, especially where larger mammal species are involved, a cause of injury, death and economic loss for motorists (Conover
et al. 1995). A range of interventions can be employed to in an attempt to reduce the animal-vehicle collision rate. One option may be to cut back vegetation along roadsides in areas with high collision rates. This could give motorists a clearer sight of animals at the roadside ahead and, hence, more chance to take avoiding action if they see an animal moving onto the road.

315Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

5.21. Modify the roadside environment to reduce collisions by reducing attractiveness of road verges to mammals

316https://www.conservationevidence.com/​actions/​2600

317One study evaluated the effects of modifying the roadside environment to reduce collisions by reducing attractiveness of road verges to mammals. This study was in Canada1.

318COMMUNITY RESPONSE (0 STUDIES)

319POPULATION RESPONSE (0 STUDIES)

320BEHAVIOUR (1 STUDY)

321Behaviour change (1 study): A replicated, before-and-after, site comparison study in Canada1 found that draining roadside salt pools and filling them with rocks reduced the number and duration of moose visits.

Background
Collisions with vehicles can be a major cause of mortality for wild mammals and, especially where larger mammal species are involved, a cause of injury, death and economic loss for motorists (Conover
et al. 1995). A range of interventions can be employed to in an attempt to reduce the animal-vehicle collision rate. One option may be to modify the roadside environment to make it less attractive to mammals. This could involve removing vegetation that provides mammals with feeding or shelter resources, planting vegetation that is unattractive to mammals or removing other roadside features that are known to attract mammals and create accident hotspots.

322Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

  • 209 Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Management of roa (...)

323A replicated, before-and-after, site comparison study in 2003–2005 in mixed coniferous and deciduous forest in Québec, Canada209 found that draining roadside salt pools and filling them with rocks reduced the number and duration of visits by moose Alces alces. There was a lower overall visit rate to salt pools at night after some were drained and filled with rocks (0.2 visits/100 hours) than before (1.5 visits/100 hours). This decline was due to a fall in visits to drained pools with visit rates to undrained pools not changing significantly (see paper for details). Daytime visits did not decrease (after: 0.2/100 hours; before: 0.2–0.5). The average length of time spent at pools decreased (after: 0.02 hours/100 hours; before: 0.11–0.18). Before management, 57 % (113/198) of recorded visits were of moose that drank the salty water. After management, no moose drank at drained pools. Moose were monitored at 12 roadside salt pools from mid-May to mid-August in 2003–2005. In autumn 2004, seven salt pools (those near most moose-vehicle collisions) were drained and filled with rocks (10–30 cm diameter) to deter moose. The other five were left untreated. Moose were monitored using movement and heat detectors that triggered a video camera or photo camera with infrared lights.

5.22. Remove roadkill regularly to reduce kill rate of predators/scavengers

324https://www.conservationevidence.com/​actions/​2601

325• We found no studies that evaluated the effects of removing roadkill regularly to reduce the kill rate of predators/ scavengers.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Animals killed on roads provide a food source for scavengers and some predators. These scavengers and predators then become vulnerable to being killed in collisions with vehicles themselves. Removing carcasses of road-killed animals thus removes a source of attraction towards roads for these species.

5.23. Modify vegetation along railways to reduce collisions by reducing attractiveness to mammals

326https://www.conservationevidence.com/​actions/​2603

327Two studies evaluated the effects of modifying vegetation along railways to reduce collisions by reducing attractiveness to wildlife. Both studies were in Norway1,2.

328COMMUNITY RESPONSE (0 STUDIES)

329POPULATION RESPONSE (2 STUDIES)

330Survival (2 studies): Two site comparison studies in Norway1,2 found that clearing vegetation from alongside railways reduced moose-train collisions.

331BEHAVIOUR (0 STUDIES)

Background
Wild mammals may be at increased risk of collisions with trains if they spend time on or close to the railway. Vegetation alongside railways may provide a feeding resource that attracts animals while, at the same time, obscuring views of oncoming trains. Removing vegetation in areas with high recorded collision rates may reduce attractiveness of such areas to mammals and, thus, reduce the risk of collision with trains.

  • 210 Jaren V., Andersen R., Ulleberg M., Pedersen P.H. & Wiseth B. (1991) Moose-train collisions: the ef (...)

332A before-and-after study, site comparison study in 1980–1988 along a railway through boreal forest in Nord-Trøndelag County, Norway210 found that vegetation removal alongside the railway reduced moose Alces alces deaths. Fewer moose were killed by trains after vegetation clearance (22 moose) than before (87 moose). Numbers also fell along uncleared sections but to a lesser extent with 27 killed after vegetation was cleared in experimental sections compared to 47 before. Vegetation clearance was estimated to be cost effective if more than 0.28 moose/km/year were expected to be killed in absence of clearance. Moose deaths were recorded along a 61-km section of railway in April–November of 1980–1988. In 1984, two sections with the highest casualties (totalling 22 km), had all bushes and trees removed from 20 m either side of the railway and all those <4 m high removed from a further 10 m width. Additional vegetation was removed at bends and on areas of browse attractive to moose. In 1986, cleared areas were sprayed with herbicide (Roundup) to reduce vegetation re-growth.

  • 211 Andreassen H.P., Gundersen H. & Storaas T. (2005) The effect of scent-marking, forest clearing, and (...)

333A site comparison study in 1985–2003 along a railway through forest in Hedmark County, Norway211 found that vegetation clearance alongside the railway reduced moose Alces alces collisions with trains. Fewer moose were killed after clearance (1.3/km/year) than before (2.6/km/year). Providing feeding stations away from the railway during winter in addition to clearing vegetation alongside the railway did not significantly further reduce collisions (5 % reduction) compared to clearing vegetation alone. Before clearance, there were 2.5 times more moose killed/km/year within treatment sections compared to comparison sections. Numbers killed/km in treatment sections were fairly constant but casualties tended to increase in comparison sections over the study period (see paper for details). Eight forest clearings (1–14 km long) were established from 1990–2002 along a 100-km-long railway section. Vegetation >30 cm high was cut each year from alongside the railway. Sections without treatments were monitored as comparison sites (49 km). Moose-train collisions were recorded from July 1985– April 2003.

5.24. Retain/maintain road verges as small mammal habitat

334https://www.conservationevidence.com/​actions/​2604

335• We found no studies that evaluated the effects of retaining or maintaining road verges as small mammal habitat.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Roads can damage or destroy grassland habitats that host a range of mammal species, especially rodents and other small mammals. Roadside verges provide habitat that can at least partly mitigate this loss for a range of small mammal species (e.g. Ascensão
et al. 2012; Bellamy et al. 2000).

336Ascensão, F., Clevenger, A., Grilo, C., Filipe, J., & Santos-Reis, M. (2012). Highway verges as habitat providers for small mammals in agrosilvopastoral environments. Biodiversity and Conservation, 21, 3681–3697, https://doi.orgdoi.org/​10.1007/​s10531-012-0390-3

337Bellamy P.E., Shore R.F., Ardeshir D., Treweek J.R. & Sparks T.H. (2000) Road verges as habitat for small mammals in Britain. Mammal Review, 30, 131–139, https://doi.org/​10.1046/​j.1365-2907.2000.00061.x

5.25. Fit vehicles with ultrasonic warning devices

338https://www.conservationevidence.com/​actions/​2606

339Three studies evaluated the effects on mammals of fitting vehicles with ultrasonic warning devices. Two studies were in the USA1,3 and one was in Australia2.

340COMMUNITY RESPONSE (0 STUDIES)

341POPULATION RESPONSE (1 STUDY)

342Survival (1 study): A replicated, controlled study in Australia found that Shu Roo warning whistles did not reduce animal-vehicle collisions for eastern grey kangaroos or red kangaroos2

343BEHAVIOUR (3 STUDIES)

344Behaviour change (3 studies): Three controlled studies (two replicated), in the USA1,3 and Australia2, found that ultrasonic warning devices did not deter mule deer1, eastern grey kangaroos2, red kangaroos2 or white-tailed deer3 from roads.

Background
Collisions between mammals such as deer and vehicles can result in death or injury to animals and humans alike. For example, it has been estimated that over 1 million deer-vehicle collisions occur annually in the USA alone (Conover
et al. 1995). Wildlife warning whistles are designed to produce high frequency, ultrasonic noises to alert or frighten animals away from oncoming vehicles. Whistles can be mounted on vehicles, with the sound being emitted once the vehicle reaches a certain speed. Alternatively, whistles can be mounted on poles or small trees along roads and be activated by headlights of approaching cars.
See also:
Install acoustic wildlife warning along roads.

345Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

  • 212 Romin L.A. & Dalton L.B. (1992) Lack of response by mule deer to wildlife warning whistles. Wildlif (...)

346A controlled study in 1990 in sagebrush in Utah, USA212 found that vehicle mounted wildlife warning whistles had no effect on the behaviour of mule deer Odocoileus hemionus. The proportions of deer that responded to the vehicle were 31 % with a whistle and 39 % without. Six percent of deer ran away from the vehicle with a whistle and 12 % did so from the vehicle without a whistle. Authors reported that they did not know if the whistles produced any sound, nor if deer heard them. Two brands of wildlife warning whistles (Game Tracker’s and Sav-a-life, producing 16–20 kHz) were mounted on the front of a truck. These were tested during late afternoon and early evening along 9.7 km of dirt road in January–February 1990. For each of 150 groups of deer (average six deer), a pass at 65 km/hour was made without and then with the whistle. Deer responses (none, head lifted, changed orientation, ran away, ran towards) and distances from the road were recorded for each pass (distances did not differ significantly between first and second passes).

  • 213 Bender H. (2001) Deterrence of kangaroos from roadways using ultrasonic frequencies: efficacy of th (...)

347A replicated, controlled study in 1997–2001 along roads in New South Wales, Queensland, Victoria and Western Australia, Australia213 found that Shu Roo warning whistles did not alter behaviour of eastern grey kangaroos Macropus giganteus or red kangaroos Macropus rufus and did not reduce kangaroo-vehicle collisions. There was no significant difference in the number of kangaroos hit by vehicles with or without whistles (22 % with; 7 % without). Vigilance responses did not differ significantly for either species when whistles were turned on (60–65 %) or off (40–75 %) and no animals fled in response. The Shu Roo was not purely ultrasonic (4–19 kHz) and was only detected at 50 m. The whistle was not detectable above the noise of the four vehicles tested. The Shu Roo (two speakers in a rectangular metal case) signal was tested in the lab and in the field at 20–400 m (static and mounted on four vehicle types). Responses of 31 captive kangaroos to the Shu Roo (turned on/ off), mounted on a vehicle at 20–50 m, was recorded on 15 occasions in July–September 1997. Fifteen companies, in which people travelled large distances (average 49,000 km) conducted surveys in four states in August 1999 to January 2001. Fifty-seven vehicles had a Shu Roo fitted and 40 vehicles did not.

  • 214 Valitzski S.A., D’Angelo G.J., Gallagher G.R., Osborn D.A., Miller K.V. & Warren R.J. (2009) Deer r (...)

348A replicated, controlled study in 2006 at a college campus in Georgia, USA214 found that high frequency sounds from moving vehicles did not reduce white-tailed deer Odocoileus virginianus behaviours that were likely to cause a deer–vehicle collision. At 0.28 kHz, there was a significant increase in the proportion of behaviours likely to cause a collision (13 %) compared to a vehicle without treatment (5 %). At four other frequencies, there was no significant difference in proportions of negative behavioural responses compared to the vehicle without treatment (1–28 kHz: 6–9 %). The proportion of behaviours likely to decrease deer-vehicle collisions did not differ between different high frequencies and no high-frequency sound (0.28 kHz: 33 %; 1 kHz: 37 %; 8 kHz: 24 %; 15 kHz: 33 %; 28 kHz: 24 %; no high-frequency sound: 35 %;). Two road sections (≥ 5 km apart), 280 m and 220 m long, were studied. For each of 319 trials, a deer was observed before and during one of six randomly assigned treatments: 0.28, 1, 8, 15 or 28 kHz or no sound. The high-frequency sounds (within deer hearing range) were played at 70 decibels from front-mounted speakers on the vehicle (48 km/hr). Deer within 10 m of the road or ahead of the vehicle were monitored from an observation platform, from 06: 00 to 09: 00 h and 19: 00 to 22: 00 h, in April and June 2006.

5.26. Install signage to warn motorists about wildlife presence

349https://www.conservationevidence.com/​actions/​2608

350Six studies evaluated the effects on mammals of installing signage to warn motorists about wildlife presence. Four studies were in the USA1,3,4,5 one was in Australia2 and one was in Canada6.

351COMMUNITY RESPONSE (0 STUDIES)

352POPULATION RESPONSE (6 STUDIES)

353Abundance (1 study): A before-and-after study in Australia2 found that when wildlife signs were installed along with speed restrictions, rumble strips, reflective wildlife deterrents, wildlife escape ramps and an educational pamphlet, a small population of eastern quoll re-established in the area.

354Survival (6 studies): Three of five studies (including four controlled and three before-and-after studies), in the USA1,3,4,5 and Canada6, found that warning signs did not reduce collisions between vehicles and deer1,3,5. The other two studies found that warning signs did reduce collisions between vehicles and deer4,6. A before-and-after study in Australia2 found that wildlife signs along with speed restrictions, rumble strips, reflective wildlife deterrents, wildlife escape ramps and an educational pamphlet, reduced collisions between vehicles and Tasmanian devils but not eastern quolls.

355BEHAVIOUR (0 STUDIES)

356OTHER (2 STUDIES)

357Human behaviour change (2 studies): Two controlled studies (one also replicated, before-and-after), in the USA1,4, found that signs warning of animals on the road reduced vehicles speeds.

Background
Wildlife crossing signs alert drivers to the potential presence of wildlife on or near a road. They encourage drivers to be more alert and/or reduce the speed of their vehicle, with the goal of reducing animal-vehicle collisions. Motorists may become habituated to signs if they are present all year round, are too common or look similar to other signs. Solutions may be to use temporary seasonal signs, animated signs, flashing lights or flags to catch the attention of drivers. Animal detection warning systems have sensors that detect large animals on or near the road that are wired to flashing signs.
Studies that investigate the effect on vehicle speed of warning signs are not included here if they do not report relevant metrics on vehicle-mammal collision rates (e.g. Lehnert & Bissonette 1997; Al-Ghamdi & AlGadhi 2004) though information on changes in motorists’ speed is reported here if the study also reports collision rates.
See also:
Reduce legal speed limit.

358Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing deer-vehicle collisions. Wildlife Society Bulletin, 25, 809–818.

359Al-Ghamdi A.S. & AlGadhi S.A. (2004) Warning signs as countermeasures to camel–vehicle collisions in Saudi Arabia. Accident Analysis & Prevention, 36, 749–760, https://doi.org/​10.1016/​j.aap.2003.05.006

  • 215 Pojar T.M., Prosencer R.A., Reed D.F. & Woodard T.N. (1975) Effectiveness of a lighted, animated de (...)

360A controlled study in 1972–1973 in Colorado, USA215 found that lighted, animated deer crossing signs reduced vehicle speeds but did not reduce deer-vehicle collisions. There was an average of one collision for each 57 deer-crossings when the signs were both on and off. Average vehicle speeds were lower with the signs on, but the reduction was by <5 km/h. Three deer carcasses at the highway edge (46, 98 and 107 m before signs) reduced speeds but the reduction did not differ between when signs were on (10 km/h reduction) or off (13 km/h reduction). Two deer crossing signs were installed along a 1.6-km-long highway section (with 97 km/h limit), where deer-vehicle collisions were frequent. Signs were reflective yellow diamonds (1.8 × 1.8 m) with four silhouettes of deer in neon tubing lighting across the sign. Signs were turned on and off for alternate weekly periods during January–March over four weeks in 1972 and 11 weeks in 1973. Numbers of deer crossing the highway were estimated by nightly spotlight counts. Collisions were recorded each night and morning. Vehicle speeds were measured at 0.2, 1.1 and 2.4 km behind the sign between 18: 00 and 22: 00 h.

  • 216 Jones M.E. (2000) Road upgrade, road mortality and remedial measures: impacts on a population of ea (...)

361A before-and-after study in 1990–1998 in Tasmania, Australia216 found that following installation of reflective wildlife signs, speed restrictions, rumble strips, reflective wildlife deterrents, wildlife escape ramps and publication of an educational pamphlet, an eastern quoll Dasyurus viverrinus population partially re-established and vehicle collisions with Tasmanian devils Sarcophilus laniarius, but not eastern quolls, decreased. Results were not tested for statistical significance. Following local extinction, 3–4 quolls re-colonised within six months of installation, increasing to ≥8 animals after two years. Road-kills were similar for quolls before and after implementation (1.6 vs 1.5/ year), but decreased for Tasmanian devils (3.6 vs 1.5/year). Following road widening in 1991, vehicle-wildlife collisions increased and quolls became locally extinct (from 19 animals). In 1996, large, reflective signs displaying a wallaby, and the words ‘Cradle Wildlife Zone’ were installed, along with the other five interventions. Animals were surveyed using 60 cage traps for three nights in alternate months in October 1990– April 1993. Then, 10–20 traps were set for 20–100 trap nights each April, May and July in 1995–1998. Spotlight counts were made once or twice in 1991, 1995, 1996 and 1998. Road-kills were recorded in 1990–1996.

  • 217 Rogers E. (2004) An ecological landscape study of deer vehicle collisions in Kent County, Michigan. (...)

362A replicated, controlled, before-and-after study in 1996–2000 along roads in three townships in Michigan, USA217 found that deer warning signs (including some of a novel design) did not reduce deer-vehicle collisions. In one township, the overall collision rate after installing standard and novel warning signs (55/year) did not differ significantly from that before installation (69/year). At the same time, there was no change in average rates in three townships without warning signs (after: 41–62/year/township; before: 36–62/year/township). There was no significant difference in average collision rates 200 feet either side of signs on seven road stretches that just had the novel sign design (after installation: 9/year/stretch; before: 11/year/stretch). Vehicle speeds were not lower with signage than without along one road stretch and were <0.5 miles/hour lower along a second stretch. Two warning sign designs were installed around one township between October and January of 1998–2000. Eighteen novel signs, (leaping deer and car on an orange background and text stating ‘High crash area’) were installed on seven road stretches with high vehicle-deer collision rates. Fifty-two standard signs (leaping deer on orange background) were installed on other sections. Collisions, monitored by State Police, were compared in the township before (1996–1997) and after installation (1998 and 2000) and in three townships without signs. Vehicle speeds were monitored for 15–24-hour periods before (1,124 vehicles) and after installation (1,221 vehicles) on two road sections.

  • 218 Sullivan T.L., Williams A.F., Messmer T.A., Hellinga L.A. & Kyrychenko S.Y. (2004) Effectiveness of (...)

363A replicated, controlled, before-and-after study in 1995–2002 along five highways in Utah, Nevada and Idaho, USA218 found that temporary warning signs reduced vehicle speeds and collisions with mule deer Odocoileus hemionus during migrations. Fewer deer deaths occurred after signs were installed (3–12/migration) than before (7–35/ migration). Concurrently, deaths did not decline on a road section without signs (after: 3–13/migration; before: 3–11/migration). Once signs were installed, the proportion of vehicles speeding (8 %) was lower than before they were installed (19 %). There was no concurrent decline on a road section without signs (after: 19 %; before: 25 %). Signs affected speeds of heavy trucks more than of passenger vehicles. Sections of five highways, crossed by mule deer seasonal migrations, were studied. Each 6.5-km-long section was divided into two with each half randomly assigned as treatment or control. Treatment sections had temporary yellow and black warning signs (2 × 1 m) with reflective flags and solar-powered flashing amber lights installed at each end and smaller signs (1 m2) each mile. Deer-vehicle collisions were monitored daily during spring and autumn migrations, before (2–4 years) and after (1–4 years) signs were installed. Night-time vehicle speeds were monitored in 2000–2001.

  • 219 Meyer E. (2006) Assessing the effectiveness of deer warning signs. Final report. KTRAN: KU-03-6.

364A before-and-after study in 1989–2004 along 22 sections of highway in Kansas, USA219 found that deer warning signs did not reduce vehicle collisions with white-tailed deer Odocoileus virginianus. The collision rate after signs were installed (0.83) did not differ from than in the 2–10 years before signs were installed (0.78; units not clear in report, but may refer to deer killed/km/year). However, the rate over just the three years after sign installation (0.71) was significantly lower than that in just the three years before installation (1.16). Numbers of collisions closely followed trends in deer populations, which increased to a peak in around 1999 and then decreased. Deer-vehicle collision data were obtained for 22 sections of highway (section lengths not stated) across seven counties for 2–10 years before and 2–5 years after deer warning signs were installed. Timing of sign installations was not known precisely but was assumed, in the report, to have been within six months of publication of Road Safety Reports, which were mostly published in 1999.

  • 220 Found R. & Boyce M.S. (2011) Warning signs mitigate deer–vehicle collisions in an urban area. Wildl (...)

365A replicated, randomized, controlled, before-and-after study in 2005–2008 at 26 urban sites around a city in Alberta, Canada220 found that warning signs reduced the number of collisions between vehicles and white-tailed deer Odocoileus virginianus. At warning sign locations, there were fewer deer-vehicle collisions after sign installation (0.4 deer-vehicle collisions/location/year) than before (1.7 deer-vehicle collisions/ location/year). Concurrently, at locations without warning signs, there was no significant difference in deer-vehicle collision rates after (1.0 deer-vehicle collisions/location/year) compared to before signs were installed (1.7 deer-vehicle collisions/location/year). Twenty-six road locations with high incidence of deer-vehicle collisions were selected. Pairs of reflective deer warning signs (90 × 90 cm, diamond shape) were mounted on 3-m-high posts, 1,600 m apart, facing opposite directions, at 13 locations (randomly selected) in June 2008. The other 13 locations had no signs installed. Deer carcasses (mostly white-tailed deer but possibly some mule deer Odocoileus hemionus) were monitored within an 800-m radius of each location from June to December in 2005–2007 (before sign installation) and in June–December 2008 (after sign installation).

5.27. Use road lighting to reduce vehicle collisions with mammals

366https://www.conservationevidence.com/​actions/​2614

367Two studies evaluated the effects on mammals of using road lighting to reduce vehicle collisions with mammals. Both studies were in the USA1,2.

368COMMUNITY RESPONSE (0 STUDIES)

369POPULATION RESPONSE (2 STUDIES)

370Survival (2 studies): One of two studies (one controlled and one before-and-after), in the USA1,2, found that road lighting reduced vehicle collisions with moose2. The other study found that road lighting did not reduce vehicle collisions with mule deer1.

371BEHAVIOUR (0 STUDIES)

Background
The risk of wildlife-vehicle collisions was found to be six times higher at night and dawn than during the day (Lavsund & Sandegren 1991). Installing lighting along roads may increase visibility of animals to motorists and may, therefore, reduce the number of collisions. However, in areas where species are sensitive to human disturbance, they may avoid areas of roads with artificial lighting and, instead, cross elsewhere.

372Lavsund S. & Sandegren F. (1991) Moose-vehicle relations in Sweden: a review. Alces, 27, 118–126.

  • 221 Reed D.F. & Woodard T.N. (1981) Effectiveness of highway lighting in reducing deer-vehicle accident (...)

373A controlled study in 1974–1979 along a highway in Colorado, USA221 found that highway lighting did not reduce vehicle collisions with mule deer Odocoileus hemionus. There was no significant difference between deer-vehicle collision rates with lights on (39 collisions from 2,611 crossings) or off (45 collisions from 2,480 crossings). Lighting did not alter the location of crossings, with accidents not occurring closer to the lights when they were off. Lighting did not alter vehicle speeds (lights on: 79 km/h; lights off: 80 km/h). Thirteen 37,000-lumen, 700- W, clear, mercury-vapour lamps (12 m high) were installed along 1.2 km of a four-lane highway (speed limit 88.5 km/h). Nine were spaced at 59–69-m intervals along 0.5 km of highway (full lighting) and two at each end were spaced at 119 and 302 m (transition lighting). Lights were alternately turned on and off for one-week periods in January– April of 1974–1979. Deer-vehicle collisions were recorded each morning and evening. Deer crossings were recorded during nightly spotlight surveys and using snow track counts. Deer behaviour was observed for two hours/night. Vehicle speeds were recorded during 35 nights in 1974.

  • 222 McDonald M.G. (1991) Moose movement and mortality associated with the Glenn Highway expansion. Alce (...)

374A before-and-after study in 1977–1990 along a highway in Alaska, USA222 found that road lighting reduced vehicle collisions with moose Alces alces. There were 65 % fewer moose-vehicle collisions when lighting was installed compared to before its installation (actual numbers not stated). There were 95 % fewer moose-vehicle collisions along the section with lighting, fencing with one-way gates and an underpass after they were installed (0.7/year) than before (17/year). Overall mortality along the entire stretch of road was lower after installation of lighting, barrier fencing and an underpass, with fewer collisions (12/year) than previously (38/year). In October 1987, road lighting was installed along 11.5 km of the highway. Fencing and 30 one-way gates were installed along 5.5 km of this section and an underpass was created. Moose-vehicle collisions were monitored before (1977–1987) and after (1987– 1990) installation.

5.28. Use chemical repellents along roads or railways

375https://www.conservationevidence.com/​actions/​2615

376Five studies evaluated the effects on mammals of using chemical repellents along roads or railways. Two studies were in Canada2,3 and one each was in Germany1, Norway4 and Denmark5.

377COMMUNITY RESPONSE (0 STUDIES)

378POPULATION RESPONSE (2 STUDIES)

379Survival (2 studies): Two studies (one before-and-after, one site comparison), in Germany and Norway1,4, found that chemical-based repellents did not reduce collisions between ungulates and road vehicles1 or trains4.

380BEHAVIOUR (4 STUDIES)

381Behaviour change (4 studies): Two of four studies (including three replicated, controlled studies), in Germany1, Canada2,3, and Denmark5, found that chemical repellents, trialled for potential to deter animals from roads, did not deter ungulates2,5. The other two studies found mixed results with repellents temporarily deterring some ungulate species in one study1 and one of three deterrents deterring caribou in the other3.

Background
Large number of mammals, especially deer and other ungulate species, are killed in collisions with road vehicles (e.g. Conover
et al. 1995) or trains. This could be reduced if the application of repellents could deter animals from accessing roads.
See also:
Agriculture & Aquaculture-Use repellents that smell bad (‘area repellents’) to deter crop or property damage by mammals to reduce human-wildlife conflict.

382Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

  • 223 Lutz W. (1994) Ergebnisse der Anwendung eines sogenannten Duftzaunes zur Vermeidung von Wildverlust (...)

383A before-and-after study in 1991–1996 at a research centre in Nordrhein-Westfalen, Germany223 found that Duftzaun scent repellent temporarily deterred some but not all large mammal species and did not reduce vehicle collisions. Red deer Cervus elaphus, roe deer Capreolus capreolus and wild boar Sus scrofa were killed on the road. There was no significant difference between numbers killed on the road when repellent was used (18/year) compared with before (13/year) or after (9/year) use (data supplied by author). In enclosure trials, mufflon Ovis orientalis (seven animals) avoided scented posts for 15 minutes. Sika deer Cervus nippon (four) avoided posts for a few minutes and roe deer (four) approached posts cautiously. Red deer (one) and fallow deer Dama dama (four) were not deterred by repellent. Trials were held in six enclosures. Duftzaun (a mixture of 10 acids integrated into a ridged foam) was applied to tops of posts supporting 50 % of daily feed and animals’ behaviours were recorded. In November 1992, a Duftzaun ‘scent fence’ was installed along a 2.8-km-long highway section where deer crossed. Scent was re-injected after four weeks and then every three months. Vehicle-wildlife collisions were recorded for two years before installation (1991–1992), three years after installation (1993–1995) and one year post-trial (1996).

  • 224 Castiov F. (1999) Testing potential repellents for mitigation of vehicle-induced mortality of wild (...)

384A replicated, controlled study in 1996–1998 in forest in Ontario, Canada224 found that 18 scent repellents (trialled for potential to deter animals from roads) did not deter white-tailed deer Odocoileus virginianris, elk Cervus canadensis nelsoni or moose Alces alces americana. Animals used a similar proportion of trails with repellents applied (63– 80 %) and of trails without repellents (62–74 %). Similarly, at mineral licks with repellents, there were fresh animal tracks on 59 % of days, which was not significantly different to the 72 % of days at mineral licks without repellents. Eighteen potential repellents were identified (from literature review) and tested on wild deer or deer, elk and moose. Repellents were mainly chemicals, including commercial repellents (Deer Away powder, Critter Ridder, mothballs) and those that simulated predators (e.g. wolf, coyote) or humans (soap, hair, clothing, sweat), but also included wolf and human silhouettes. Use of pairs of trails through snow (up to 240 pairs) with head-height repellents or without repellents, were monitored by counting tracks in winter 1997 or 1998. Repellents were also tested at a mineral lick. Use of this was monitored by track counts and an infra-red camera on days with and without repellents, in summer 1997.

  • 225 Brown W.K., Hall W.K., Linton L.R., Huenefeld R.E. & Shipley L.A. (2000) Repellency of three compou (...)

385A replicated, controlled study in 1998 in three captive facilities in Alberta, Canada225 found that one of three repellents (trialled for potential to deter animals from roads) discouraged feeding by caribou Rangifer tarandus. Animals ate significantly less food treated with lithium chloride (day 1: 900 g consumed; days 2–5: 200–300 g/day) than untreated food (1,200 g/day). Caribou ate significantly less food treated with Deer Away Big Game Repellent® on day 1 (300 g consumed) but not days 2–5 (700–900 g/day) compared to untreated food (1,200 g/ day). Wolfin® did not affect the amount eaten (days 1–5: 1,100 g/day; untreated: 1,100 g/day). Lithium chloride (a gastrointestinal toxicant), Deer Away Big Game Repellent® (olfactory and taste repellent) and Wolfin® (olfactory repellent stimulating wolf urine), which could each be added to salt-sand mixtures or placed along roads to discourage salt licking, were tested on 14 captive caribou at three sites. Big Game Repellent powder (12–15 g/kg pellets) and lithium chloride (150 mg/ kg body mass) were put on pelleted food. Wolfin capsules (5 cm) were placed on 1-m-high posts, 2 m from pellets. Food was provided without repellent for two days before and after a five-day period with repellents, in February–May 1998.

  • 226 Andreassen H.P., Gundersen H. & Storaas T. (2005) The effect of scent-marking, forest clearing, and (...)

386A before-and-after, site comparison study in 1985–2003 along a railway through forest in Hedmark County, Norway226 found that chemical scent-based repellent did not reduce moose Alces alces collisions with trains. In scent-marked areas, there was an average of 0.3 collisions/km/ year when scent marks were applied compared to 1.8/km/year before. However, there was large variation in effectiveness between sections and the reduction was not statistically significant. Numbers killed/km/year in non-treated sections tended to rise over the study period (see paper for details). Along a 100-km-long stretch of railway, ten 500-m-long sections were sprayed with repellent during the winter of 1994–1995 and a further 10 in 1995–1996, during the first days when snow exceeded 20 cm depth. The repellent ‘Duftzaun’ (components from brown bear Ursus arctos, wolf Canis lupus, lynx Lynx lynx and humans) was sprayed on trees and bamboo canes at 5-m intervals. One treatment lasted 3–4 months. Sections without treatment (total 49 km) were also monitored. Moose-train collisions were recorded from July 1985–April 2003.

  • 227 Elmeros M., Winbladh J.K., Andersen P.N., Madsen A.B. & Christensen J.T. (2011) Effectiveness of od (...)

387A replicated, controlled, before-and-after study in 2006 in a conifer plantation in Denmark227 found that the repellents Mota FL and Wolf Urine (trialled for potential to deter animals from roads) did not reduce visits by deer. Roe deer Capreolus capreolus visited a similar number of Moto FL-treated plots after application (6–8 plots/day) and before (4–8 plots/day). Visit rates to untreated plots were similar after application in treatment plots (7–8 plots/day) compared to before (5–8 plots/day). The same pattern held for red deer Cervus elaphus treatment plots (after: 1–3 plots/day); before: 0–4 plots/day) and untreated plots (after: 2–4 plots/day; before: 0–3 plots/day). Roe deer visited a similar number of Wolf Urine-treated plots after application (7–9 plots/day) and before (7–9 plots/day). Visit rates to untreated plots were similar after application in treatment plots (6–9 plots/day) compared to before (6–9 plots/day). The same pattern held for red deer treatment plots (after: 1–4 plots/day; before: 1–3 plots/day) and untreated plots (after: 0–4 plots/day; before: 0–4 plots/day). Eighteen sand arenas (4 m diameter, ≥400 m apart) included nine for repellent treatments and nine controls. Arenas were baited with beet and maize every 3–4 days or as required, for two months. Deer tracks were monitored daily for seven days before repellent was sponged onto four scent posts at each treatment arena. Track monitoring continued for seven further days. Mota FL was assessed from 7–21 February 2006. Repellent posts were then cleaned with alcohol and Wolf Urine assessed from 8–22 March 2006.

5.29. Use alternative de-icers on roads

388https://www.conservationevidence.com/​actions/​2616

389• We found no studies that evaluated the effects on mammals of using alternative de-icers on roads.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Use of chloride salts as de-icers along roads in winter can attract wildlife and may therefore increase vehicle-wildlife collisions, particularly in areas without natural salt licks. The main de-icers used by highway agencies are chloride-based salts such as sodium chloride, calcium chloride or magnesium chloride, or acetate-based de-icers such as potassium, sodium or calcium magnesium acetate. Reducing the amount of salt used or using alternative de-icers without salt, particularly in areas with high vehicle-wildlife collision rates, may reduce the attractiveness of roadsides to wildlife.
A study in Canada found that filling roadside salt pools with rocks (thus rendering them unavailable as salt-lick sources) reduced the number and duration of visits by moose
Alces alces (Leblond et al. 2007; see Modify the roadside environment to reduce collisions by reducing attractiveness of road verges to mammals).

390Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Management of roadside salt pools to reduce moose–vehicle collisions. The Journal of Wildlife Management, 71, 2304–2310, https://doi.orgdoi.org/​10.2193/​2006-459

5.30. Provide food/salt lick to divert mammals from roads or railways

391https://www.conservationevidence.com/​actions/​2617

392Three studies evaluated the effects of providing food or salt licks to divert mammals from roads. One study was in the USA1, one was in Norway2 and one was a review of studies from across North America and Europe3.

393COMMUNITY RESPONSE (0 STUDIES)

394POPULATION RESPONSE (2 STUDIES)

395Survival (2 studies): A replicated, controlled study in the USA1 found that intercept feeding reduced mule deer road deaths along two of three highways in one of two years. A replicated, site comparison study in Norway2 found that intercept feeding reduced moose collisions with trains.

396BEHAVIOUR (1 STUDY)

397Behaviour change (1 study): A review of feeding wild ungulates in North America, and Europe3 found that feeding diverted ungulates away from roads in one of three studies.

Background
‘Intercept feeding’ provides supplemental food sources in a particular location in an attempt to divert animals away from roads or railways. It is typically used as a technique aimed at ungulates, which can account for a large number of collisions between vehicles and wildlife (e.g. an estimated >1 million deer-vehicle collisions annually in the USA, Conover
et al. 1995).

398Conover M.R., Pitt W.C., Kessler K.K., DuBow T.J. & Sanborn W.A. (1995) Review of human injuries, illnesses, and economic losses caused by wildlife in the United States. Wildlife Society Bulletin, 23, 407–414.

  • 228 Wood P. & Wolfe M.L. (1988) Intercept feeding as a means of reducing deer-vehicle collisions. Wildl (...)

399A replicated, controlled study in 1985–1986 along three highways in Utah, USA228 found that intercept feeding reduced mule deer Odocoileus hemionus road deaths along two of three highways in one of two years. In the first year, the numbers of mule deer killed on road sections with intercept feeding (8–19 deer killed) were not significantly different to the numbers killed on those without (14–31). The following year, roads kills were lower on two highway sections with intercept feeding (with feeding: 34–38 deer killed; without: 59–89), but higher with feeding on the third (feeding: 31; without: 13). Feeding stations were closer to this third highway (0.4 km) than to the others (0.8–1.2 km). Road-kill deer were recorded along three highways, within 21–24-km-long sections. Highways were divided into a treatment (feed) and control (no-feed) section of equal length (8.3 or 9.6 km), separated by a shorter buffer zone (4.2 or 4.8 km). Treatment and control sections were swapped in the second year. There were four feeding stations/treatment section. Alfalfa hay, deer pellets and apple mash were provided 1–3 times/3 days from January to mid-March of 1985 and 1986.

  • 229 Andreassen H.P., Gundersen H. & Storaas T. (2005) The effect of scent-marking, forest clearing, and (...)

400A replicated, site comparison study in 1985–2003 along a railway through forest in Hedmark County, Norway229 found that intercept feeding stations reduced moose Alces alces collisions with trains. There was an estimated 40 % collision reduction following feeding station establishment, equating to six fewer moose collisions/year. Providing intercept feeding stations and clearing vegetation >30cm high from alongside the railway did not significantly further reduce collisions (5 % reduction) compared to implementing just one of these treatments. Before providing feeding stations, 2.5 times more moose were killed/ km/year within treatment sections compared to comparison sections. Numbers killed/km in treatment sections were fairly constant but casualties increased in comparison sections over the study period. Moose feeding stations were established, in 1995, along a 100-km-long railway section. Feeding stations were in side-valleys, linked to three railway sections (4, 6 and 8 km long). Landowners provided food during the winter, using baled grasses and silage and/or herbs, from when snow accumulated until April–May. Sections without treatments were also monitored (total 49 km long). Moose-train collisions were recorded from July 1985–April 2003.

  • 230 Milner J.M., van Beest F.M., Schmidt K.T., Brook R.K. & Storaas T. (2014) To feed or not to feed? E (...)

401A review of evidence within studies looking at effects of feeding wild ungulates in North America, Fennoscandia and elsewhere in Europe230 found that diversionary feeding diverted ungulates away from roads in one of three studies. No such effect was found in the other two studies. The review also assessed evidence for supplementary feeding affecting survival and morphological characteristics. In total, the review reported evidence from 101 studies that met predefined criteria from an initial list of 232 papers and reports. Three of these studies investigated the effectiveness of feeding for diverting ungulates away from roads.

402feeding wild ungulates. The Journal of Wildlife Management, 78, 1322–1334, https://doi.org/​10.1002/​jwmg.798

5.31. Use reflective collars or paint on mammals to reduce collisions with road vehicles

403https://www.conservationevidence.com/​actions/​2619

404• We found no studies that evaluated the effects of using reflective collars or paint on mammals to reduce collisions with road vehicles.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Fitting collars with reflective tape on animals to increase their visibility to drivers was considered in Canada for reintroduced wood bison
Bos bison (Huijser et al. 2007). In Finland, a spray that reflects vehicle headlights was applied to the antlers of reindeer with the aim of making the animals more visible to motorists and so reducing collisions with vehicles (https://www.ibtimes.co.in/​finnish-reindeer-given-glowing-antlers-to-prevent-accidents-539561).

405Huijser M.P., McGowen P., Fuller J., Hardy A., Kociolek A., Clevenger A.P., et al. (2007) Wildlife–vehicle collision reduction study. Report to Congress. U.S. Department of Transportation, Federal Highway Administration, Washington D.C., USA.

5.32. Use wildlife decoy to reduce vehicle collisions with mammals

406https://www.conservationevidence.com/​actions/​2620

407• We found no studies that evaluated the effects of using wildlife decoys to reduce vehicle collisions with mammals.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Animal silhouettes made of wood, Styrofoam or cardboard, or models or stuffed animals, placed along the edge of roads, may remind people to slow down in certain areas where animals are commonly hit. Reduced vehicles speeds may help to reduce vehicle-wildlife collisions. One small study found that a stuffed deer did reduce vehicle speeds (Reed & Woodard 1981) but did not assess whether or not this resulted in fewer collisions between vehicles and animals.

408Reed D.F. & Woodard T.N. (1981) Effectiveness of highway lighting in reducing deer-vehicle accidents. The Journal of Wildlife Management, 45, 721–726.

5.33. Close roads in defined seasons

409https://www.conservationevidence.com/​actions/​2626

410One study evaluated the effects on mammals of closing roads in defined seasons. This study was in the USA1.

411COMMUNITY RESPONSE (0 STUDIES)

412POPULATION RESPONSE (0 STUDIES)

413BEHAVIOUR (1 STUDY)

414Use (1 study): A site comparison study in the USA1 found that closing roads to traffic during the hunting season increased use of those areas by mule deer.

Background
Some mammals may avoid areas around roads (e.g. Rost & Bailey 1979). Closing these roads to traffic, especially at times of the year when they most use the habitat that the road runs through, may increase their use of such areas and, hence, increase their access to natural resources such as food and shelter.

415Rost G.R. & Bailey J.A. (1979) Distribution of mule deer and elk in relation to roads. The Journal of Wildlife Management, 43, 634–641.

  • 231 Curtis A.M. & Du Toit J.T. (2017) Efficacy of travel management areas for reducing disturbance to m (...)

416A site comparison study in 2015 in a forest in Oregon, USA231 found that closing roads to traffic during the hunting season increased use of those areas by mule deer Odocoileus hemionus. Mule deer positions were closer to closed roads (average 190 m) than to open roads (average 1,250 m). In March 2015, an unspecified number of mule deer were captured and fitted with GPS collars that recorded their location every 13 hours. Deer locations and distances to the nearest road were recorded in August–October 2015. During this period, an unspecified number of roads in the area were closed to vehicles, while others remained open. This period overlapped with the legal hunting season.

Utility & Service Lines

5.34. Install crossings over/under pipelines

417https://www.conservationevidence.com/​actions/​2627

418Three studies evaluated the effects on mammals of installing crossings over/under pipelines. Two studies were in the USA1,2 and one was in Canada3.

419COMMUNITY RESPONSE (0 STUDIES)

420POPULATION RESPONSE (0 STUDIES)

421BEHAVIOUR (3 STUDIES)

422Use (3 studies): A study in USA1 found that buried pipeline sections were used more frequently than their availability as crossing points by caribou. A study in USA2 found that pipeline sections elevated specifically to permit mammal crossings underneath were not used by moose or caribou more than were other elevated sections. A controlled study in Canada3 found that a range of large mammal species used wildlife crossings over pipelines.

Background
Pipelines can extend hundreds of kms and may represent substantial barriers to mammal movements if they lie at or just above the surface of the ground. Crossing points can be either elevated sections of pipe with space for mammals to pass beneath, buried sections or sections with crossing ramps constructed over the pipe.

  • 232 Curatolo J.A. & Murphy S.M. (1986) The effects of pipelines, roads, and traffic on the movements of (...)

423A study in 1981–1983 of three sites along a pipeline across tundra in Alaska, USA232 found that buried pipeline sections were used more frequently than their availability as crossing points by caribou Rangifer tarandus. Buried pipeline sections accounted for 10 of 180 crossings (6 %) at one site, 5 of 41 crossings (12 %) at a second site and 65 of 732 crossings (9 %) at a third site. These proportions were all higher than the proportion of pipeline that was buried at these sites (2 %). Ramps (20–50 m wide) were installed across buried pipeline sections at three study sites. Sites covered 180–275 ha, each including 1.7–2.2 km of pipeline. Sections not buried were elevated 1.2–4.3 m above the ground. A crossing comprised one or more caribou crossing the pipeline, with >50 % of group members successfully crossing. Crossings were documented by direct observations in late June to early August of 1981–1983.

  • 233 Eide S.H., Miller S.D. & Chihuly M.A. (1986) Oil pipeline crossing sites utilized in winter by moos (...)

424A study in 1977–1978 of a pipeline across tundra in Alaska, USA233 found that pipeline sections elevated specifically to permit crossings of animals underneath were not used by moose Alces alces or caribou Rangifer tarandus more than were other elevated sections. Of 81 crossing sections elevated to facilitate mammal crossings, 13 (16 %) were used by moose, a similar rate to the 754 of 6,526 other elevated sections (12 %) that were crossed. Caribou used four of 53 specifically elevated crossing sections (8 %) available to them, a lower rate than the 10 % of remaining elevated sections used as crossing points. Along a 145-km-long pipeline, 81 pipe sections were elevated specifically to permit large mammal passage underneath. These sections were ≥3 m high. Remaining sections, were of variable, but generally lower, height. All elevated pipe sections were 18.3 m long between supports. Animal passage was determined by footprint surveys after fresh snow. The pipe, separated into three sections, was surveyed on 11–15 occasions in October 1977–February 1978 and 1–5 occasions in March–April 1978.

  • 234 Dunne B.M. & Quinn M.S. (2009) Effectiveness of above-ground pipeline mitigation for moose (Alces a (...)

425A controlled study in 2006–2007 in boreal mixed-woodland in Alberta, Canada234 found that mammals used wildlife crossings over oil pipelines. Camera-trapping showed that successful crossings were made by deer (white-tailed deer Odocoileus virginianus and mule deer Odocoileus hemionus) on 746 of 904 approaches (83 %), by moose Alces alces on 157 of 178 approaches (88 %) and by coyotes Canis latrans on 52 of 59 of approaches (88 %). Crossings were also made by lynx Lynx canadensis and black bear Ursus americanus (twice each) and gray wolf Canis lupus (once). Snow-tracking showed that deer had a higher successful pipeline crossing rate at wildlife crossings (96 % of approaches) than along pipeline sections without crossings (90 %). Moose success rate at crossings (66 %) was lower than on sections without crossings (77 %). In March 2006, five crossing structures of soil and vegetation (≥20 m long, ≥4 m wide, 2–3 m high) were installed along 5.5 km of pipeline. Use of these crossings, and of gaps under elevated sections along 1.6 km of pipeline, was monitored. Snow track surveys were carried out at three-week intervals in February–March 2006 and November 2006– April 2007. Camera traps were installed along each pipeline section with two at each crossing for one year (2006–2007).

Shipping Lanes

5.35. Install overpasses over waterways

426https://www.conservationevidence.com/​actions/​2628

427Two studies evaluated the effects on mammals of installing overpasses over waterways. One study was in the USA1 and one was in Spain2.

428COMMUNITY RESPONSE (0 STUDIES)

429POPULATION RESPONSE (0 STUDIES)

430BEHAVIOUR (2 STUDIES)

431Use (2 studies): Two studies (one replicated, one a site comparison) in the USA1 and Spain2, found that bridges and overpasses over waterways were used by desert mule deer, collared peccaries and coyotes1 and by a range of large and medium-sized mammals2.

Background
Waterways can separate populations of a species or provide barriers to movements. Artificial waterways (such as canals and aqueducts) can disrupt movements between previously connected habitat. This may result in genetic isolation of populations (e.g. Corlatti
et al. 2009) or drownings, if animals attempt to cross waterways that have steep sides. Crossing points may be installed for use of animals in an attempt to maintain connectivity and free movement between sites or habitats.
See also:
Install barrier fencing along waterways and Provide mammals with escape routes from canals.

432Corlatti L., Hackländer K. & Frey-Roos F. (2009) Ability of wildlife overpasses to provide connectivity and prevent genetic isolation. Conservation Biology, 23, 548–556, https://doi.org/​10.1111/​j.1523-1739.2008.01162.x

  • 235 Popowski R.J. & Krausman P.R. (2002) Use of crossings over the Tucson aqueduct by selected mammals. (...)

433A site comparison study in 1996–1997 along an aqueduct in Arizona, USA235 found that overpasses over a waterway within a created wildlife corridor were used by desert mule deer Odocoileus hemionus eremicus, collared peccaries Pecari tajacu and coyotes Canis latrans. Mule deer and peccaries used all six wildlife overpasses inside the corridor. Bridges outside the corridor, not designed for wildlife, were also used. However, there were more mule deer tracks on wildlife overpasses inside the corridor (average 0.06–0.11 tracks/reading) than on bridges outside the corridor (0–0.01 tracks/reading). The same held for peccaries (wildlife overpasses: 0.15–0.21 tracks/reading; bridges: 0.06–0.17). There was no difference for coyotes (wildlife overpasses: (0.28–0.45 tracks/reading; bridges: 0.31–0.59). Aqueduct crossings were provided at five points within and one immediately adjacent to the corridor. Crossings were 9–173 m wide. Four crossings to the north were also monitored along 11 km of aqueduct. Crossings within the corridor contained natural soil and vegetation. Those outside were concrete overchutes or overpasses of water. Animal tracks were recorded on sand plots (2–22/crossing) on ≥7 consecutive days/month from August 1996 to July 1997 (total 117 checks/plot).

  • 236 Peris S. & Morales J. (2004) Use of passages across a canal by wild mammals and related mortality. (...)

434A replicated study in 1993–1998 along a canal in Guardo, northern Spain236 found that all nine small bridges and six of 14 wider bridges designed for humans and livestock were used as crossing points by mammals. Crossings were made by roe deer Capreolus capreolus (four crossings), red deer Cervus elaphus (four), wild boar Sus scrofa (nine), wolf Canis lupus (three), fox (52) and by mustelids, mainly badgers Meles meles and stone martens Martes foina (14). Iberian hares Lepus granatensis and hedgehogs Erinaceus europaeus were also recorded. Small wildlife bridges were used more than were larger bridges by all mammals as a whole (see paper for details) and bridges near scrubland were used more (12 out of 13 used) than were those near cropland (one out of nine used). Despite crossings being available, 123 roe deer and 34 wild boars were found drowned over the five years. Fourteen concrete bridges (for humans and livestock; 5.0–7.5 m wide) and nine small wildlife bridges (2.5–3.6 m wide) along 24 km of a 5-m-wide concrete water canal were monitored. Tracks in sand and other animal signs were recorded on each bridge every three days from April to September 1998. Drowned mammals were monitored daily from April 1993 to October 1998.

5.36. Install barrier fencing along waterways

435https://www.conservationevidence.com/​actions/​2636

436• We found no studies that evaluated the effects on mammals of installing barrier fencing along waterways.

‘We found no studies’ means that we have not yet found any studies that have directly evaluated this intervention during our systematic journal and report searches. Therefore, we have no evidence to indicate whether or not the intervention has any desirable or harmful effects.

Background
Mammals may be attracted to canals and other waterways for drinking. When such waterways have steep sides, mammals may fall in and be unable to escape. Waterways may also act as barriers to animal movements and mammals may attempt to cross them but be unable to exit the water. In such cases, mammals may be at risk of drowning (e.g. Peris & Morales 2004). At areas of high risk, barrier fencing could be installed in order to prevent mammals accessing waterways and so reduce the drowning risk.

437Peris S. & Morales J. (2004) Use of passages across a canal by wild mammals and related mortality. European Journal of Wildlife Research, 50, 67–72, https://doi.orgdoi.org/​10.1007/​s10344-004-0045-0

5.37. Provide mammals with escape routes from canals

438https://www.conservationevidence.com/​actions/​2638

439Five studies evaluated the effects on mammals of providing mammals with escape routes from canals. Two studies were in Germany1,2 and one each was in the USA3, the Netherlands4 and Argentina5.

440COMMUNITY RESPONSE (0 STUDIES)

441POPULATION RESPONSE (2 STUDIES)

442Survival (2 studies): One of two studies (one before-and-after), in Germany2 and the USA3, found that ramps and ladders reduced mule deer drownings3 whilst the other study found that ramps and shallow-water inlets did not reduce mammal drownings2.

443BEHAVIOUR (3 STUDIES)

444Use (3 studies): Three studies (one replicated) in Germany1, the Netherlands4 and Argentina5, found that ramps and other access or escape routes out of water were used by a range of medium-sized and large mammal species.

Background
Mammals may be attracted to canals and other artificial waterways for drinking. When such waterways have steep sides, mammals may fall in and be unable to escape. Such waterways may also act as barriers to animal movements and mammals may attempt to cross them but be unable to exit the water whilst some aquatic mammals may also enter deliberately but struggle to exit the water. In such cases, mammals may be at risk of drowning (e.g. Peris & Morales 2004). Escape routes may be installed to enable mammals that have fallen in or otherwise entered the water to escape back onto land. These may take the form or ramps, ladders, shallow inlets or other structures that mammals could use to climb out.

445Peris S. & Morales J. (2004) Use of passages across a canal by wild mammals and related mortality. European Journal of Wildlife Research, 50, 67–72, https://doi.orgdoi.org/​10.1007/​s10344-004-0045-0

  • 237 Schneider V.E. & Waffel H.H. (1978) Vorschläge zu Schutzmaßnahmen für Wildtiere beim Ausbau von Sch (...)

446A study (year not stated) in a swimming pool and on a stretch of a canal in Lower Saxony, Germany237 found that a platform was used by at least five mammal species to exit water and both metal ramps and vegetated islands by at least two species Roe deer Capreolus capreolus, red deer Cervus elaphus, wild boar Sus scrofa, red foxes Vulpes vulpes and badgers Meles meles used timber platforms to exit from waterways. Rabbits Oryctolagus cuniculus and hedgehogs Erinaceus europaeus used a ramp covered with meshed metal to exit from waterways. Red foxes and badgers used vegetated islands to leave water. Timber platforms were tested by releasing medium-sized (e.g. foxes) and large mammals (e.g. deer) into a swimming pool, and guiding them to a platform. A ramp covered with meshed metal was tested for small mammals (e.g. rabbits) and a ‘vegetated island’ (4.5 m × 2.5 m; 1.5 m above water level) was tested for deer, badgers and foxes. The vegetated island comprised timber beams ‘planted’ with leafy branches either fixed to the bank or anchored in the middle of a steep-banked stretch of canal.

  • 238 Wietfeld J. (1984) Die Wirksamkeit von Schutzmaßnahmen zur Verhinderung von Tierverlusten in verspu (...)
  • 239 Rautenstrauch K.R. & Krausman P.R. (1989) Preventing mule deer drownings in the Mohawk canal, Arizo (...)

447A before-and-after, site comparison study in 1978–1982 of a steep-sided canal in Germany238 239found that installing shallow-water inlets and ramps did not reduce mammal drownings. There was no evidence of large mammals leaving the canal by inlets or of a reduction in the number drowned after inlet establishment (after: 15 individuals drowned in one year; before: 11 drowned in two years). There was no evidence of small mammals using ramps as exits. There was no significant difference in the density of drowned small mammals on canal sections with and without ramps where the length of canal surveyed without ramps was twice the length surveyed with ramps: hamster Cricetus cricetus (with: 50; without: 80), common vole Microtus arvalis (with: 14; without: 25), water vole Arviola terrestris (with: four; without: seven). Inlets were shallow shelving exit points (250–500 m apart) established in spring 1979. Sand at eight inlet entrances was checked daily in September 1979, and April–May of 1980 and 1981 for mammal footprints. The canal was searched every 2–3 days for drowned animals before and after inlet establishment (1978–1980). Ramps (≤50 m apart) were installed in May 1982. Sand at ramp exits was checked daily over 20 days in August for small mammal footprints. Live-trapping was conducted over 13 days.

  • 240 Schneider V.E. & Waffel H.H. (1978) Vorschläge zu Schutzmaßnahmen für Wildtiere beim Ausbau von Sch (...)

448A study in 1982–1985 in a canal between farmland and desert in Arizona, USA240 found that ramps and ladders reduced mule deer Odocoileus hemionus drownings. Of at least 282 times that deer fell into the canal over a 40-month period, three deer drowned, 116 escaped via steps, 79 via ramps and eight via metal ladders. A further 50 escaped without using structures and 10 were pulled out alive. Exit points of 16 deer were not determined. Over two previous years, before escape routes were improved, 18 deer drowned on the same canal section. A 15-km-long canal section, 5.5–10 m wide was studied. There were six dams, five with existing escape stairs. In 1980–1981, three escape ramps (3 m wide, at 25° to the direction of water flow with a 25 % slope) were added. There was also one 1.3-m-wide iron ladder and seven reinforcement-bar ladders (date of installation not stated). Wire cables (3 cm diameter) across the water surface, directed trapped deer toward each escape structure. Deer were monitored and reported by canal workers and by monitoring tracks at 1–3-day intervals in June 1982 to September 1985 (total 478 visits). Drownings in 1979–1980 were logged by canal staff.

  • 241 Lammertsma D., Niewold F., Jansman H., Kuiters L., Koelewijn H.P., Haro M.P., van Adrichem M., Boer (...)

449A study in 2002–2005 in two wetland areas in the Netherlands241 found that providing mammals with escape or access routes from and into canals resulted in their use by Eurasian otters Lutra lutra. In 2002–2005, twenty-four animals, comprising a mix of wild-caught and captive-bred individuals, were released at two sites. In one of the areas, modifications to canal banks were made to aid entry and exit by otters to and from the water. Use of exits from canals was monitored by direct observation, observation of tracks in the snow, and identification of otter faeces.

  • 242 Albanesi S.A., Jayat J.P. & Brown A.D. (2016) Mortalidad de mamíferos y medidas de mitigación en ca (...)

450A replicated study in 2012–2015 of two irrigation canals in Jujuy, Argentina242 found that at least three mammal species used escape ramps to exit from waterways. Two tapirs Tapirus terrestris, one collared peccary Pecari tajacu and one Mazama americana were recorded exiting water via ramps. Thirteen additional mammal species were detected on escape ramps though it is unclear if they used these to exit from water. Two irrigation canals were studied, one crossing a forest reserve and the other crossing sugar cane and citrus plantations. In 2012–2013, fifteen 3-m-wide escape routes with 20-cm-high steps were constructed. Escape routes were 0.15–1.8 km apart. Monitoring was conducted using camera traps set in October 2012, May 2013, March 2014 and December 2015. Camera traps were 2–3 m from escape routes and were set to take one photo every 5 minutes for approximately 40 days.

Note

1 Mansergh I.M. & Scotts D.J. (1989) Habitat continuity and social organisation of the mountain pygmy-possum restored by tunnel. The Journal of Wildlife Management, 53, 701–707, https://doi.org/10.2307/3809200

2 Woelfel H. & Krueger H.H. (1995) Zur Gestaltung von Wilddurchlässen an Autobahnen [On the design of game passages across highways]. Zeitschrift für Jagdwissenschaft, 41, 209–216, https://doi.org/10.1007/bf02239950

3 Yanes M., Velasco J. & Suarez F. (1995) Permeability of roads and railways to vertebrates: the importance of culverts. Biological Conservation, 71, 217–222, https://doi.org/10.1016/0006-3207(94)00028-o

4 Rosell C., Parpal J., Campeny R., Jove S., Pasquina A. & Velasco J.M. (1997) Mitigation of barrier effect on linear infrastructures on wildlife. Pages 367– 372 in: Habitat Fragmentation & Infrastructure. Ministry of Transport, Public Works and Water Management, Delft, Netherlands.

5 Norman T., Finegan A. & Lean B. (1998) The role of fauna underpasses in New South Wales. Proceedings -International Conference on Wildlife Ecology and Transportation, Florida Department of Transportation, Tallahassee, Florida, USA, 195–208.

6 Veenbaas G. & Brandjes J. (1999) Use of fauna passages along waterways under highways. Proceedings -International Conference on Wildlife Ecology and Transportation, Florida Department of Transportation, Tallahassee, Florida, USA, 253–258.

7 Austin J.M. & Garland L. (2001) Evaluation of a wildlife underpass on Vermont State Highway 289 in Essex, Vermont. Proceedings -2001 International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 616–624.

8 Clevenger A.P., Chruszcz B. & Gunson K. (2001) Drainage culverts as habitat linkages and factors affecting passage by mammals. Journal of Applied Ecology, 38, 1340–1349, https://doi.org/10.1046/j.0021-8901.2001.00678.x

9 Fitzgibbon K. (2001) An evaluation of corrugated steel culverts as transit corridors for amphibians and small mammals at two Vancouver Island wetlands and comparative culvert trials. MA thesis. Royal Roads University, Vancouver, Canada.

10 Little S.J., Harcourt R.G. & Clevenger A.P. (2002) Do wildlife passages act as prey-traps? Biological Conservation, 107, 135–145, https://doi.org/10.1016/S0006-3207(02)00059-9

11 Tigas L.A., Van Vuren D.H. & Sauvajot R.M. (2002) Behavioral responses of bobcats and coyotes to habitat fragmentation and corridors in an urban environment. Biological Conservation, 108, 299–306, https://doi.org/10.1016/s0006-3207(02)00120-9

12 Foresman K.R. (2003) Small mammal use of modified culverts on the Lolo South project of western Montana — an update. Proceedings -International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 342–343

13 LaPoint S., Keys R.W. & Ray J.C. (2003) Animals crossing the Northway: are existing culverts useful? Adirondack Journal of Environmental Studies, 10, 11–17.

14 Ng S.J., Dole J.W., Sauvajot R.M., Riley S.P.D. & Valone T.J. (2004) Use of highway undercrossings by wildlife in southern California. Biological Conservation, 115, 499–507, https://doi.org/10.1016/S0006-3207(03)00166-6

15 Goosem M., Weston N. & Bushnell S. (2005) Effectiveness of rope bridge arboreal overpasses and faunal underpasses in providing connectivity for rainforest fauna. Proceedings -International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 304–318.

16 Krawchuk A., Larsen K.W., Weir R.D. & Davis H. (2005) Passage through a small drainage culvert by mule deer, Odocoileus hemionus, and other mammals. The Canadian Field Naturalist, 119, 296–298, https://doi.orgdoi.org/10.22621/cfn.v119i2.119

17 Choi T.-Y. & Park C.H. (2007) Can wildlife vehicle collision be decreased by increasing the number of wildlife passages in Korea? Proceedings — International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 392–400.

18 Choi T.-Y. & Park C.H. (2007) Can wildlife vehicle collision be decreased by increasing the number of wildlife passages in Korea? Proceedings — International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 392–400.

19 LaPoint S., Keys R.W. & Ray J.C. (2003) Animals crossing the Northway: are existing culverts useful? Adirondack Journal of Environmental Studies, 10, 11–17.

20 Foresman K.R. (2003) Small mammal use of modified culverts on the Lolo South project of western Montana — an update. Proceedings -International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 342–343

21 Donaldson B. (2007) Use of highway underpasses by large mammals and other wildlife in Virginia: factors influencing their effectiveness. Transportation Research Record: Journal of the Transportation Research Board, 2011, 157–164.

22 Kleist A.M., Lancia R.A. & Doerr P.D. (2007) Using video surveillance to estimate wildlife use of a highway underpass. The Journal of Wildlife Management, 71, 2792–2800, https://doi.org/10.3141%2F2011-17

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40 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyoming. Transportation Research Record, 859, 8–13.

41 Cain A.T., Tuovila V.R., Hewitt D.G. & Tewes M.E. (2003) Effects of a highway and mitigation projects on bobcats in Southern Texas. Biological Conservation, 114, 189–197, https://doi.org/10.1016/S0006-3207(03)00023-5

42 Villalva P., Reto D., Santos-Reis M., Revilla E. & Grilo C. (2013) Do dry ledges reduce the barrier effect of roads? Ecological Engineering, 57, 143–148, https://doi.org/10.1016/j.ecoleng.2013.04.005

43 Collinson W.J., Davies-Mostert H.T. & Davies-Mostert W. (2017) Effects of culverts and roadside fencing on the rate of roadkill of small terrestrial vertebrates in northern Limpopo, South Africa. Conservation Evidence, 14, 39–43.

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45 Rodriguez A., Crema G. & Delibes M. (1996) Use of non-wildlife passages across a high speed railway by terrestrial vertebrates. Journal of Applied Ecology, 33, 1527–1540, https://doi.org/10.2307/2404791

46 Keller V. (1999) The use of wildlife overpasses by mammals: results from infrared video surveys in Switzerland, Germany, France, and the Netherlands. Proceedings of the 5th Infra Eco Network Europe Conference, Budapest, Hungary, 27–28.

47 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicle collisions. Wildlife Society Bulletin, 29, 646– 653, https://doi.org/10.2307/3784191

48 van Wieren S.E. & Worm P.B. (2001) The use of a motorway wildlife overpass by large mammals. Netherlands Journal of Zoology, 51, 97–105, https://doi.orgdoi.org/10.1163/156854201X00071

49 McDonald W. & St Clair C.C. (2004) Elements that promote highway crossing structure use by small mammals in Banff National Park. Journal of Applied Ecology, 41, 82–93, https://doi.org/10.1111/j.1365-2664.2004.00877.x

50 Clevenger A.P. & Waltho N. (2005) Performance indices to identify attributes of highway crossing structures facilitating movement of large mammals. Biodiversity and Conservation, 121, 453–464, https://doi.org/10.1016/j.biocon.2004.04.025

51 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2005) Complementary use by vertebrates of crossing structures along a fenced Spanish motorway. Biological Conservation, 124, 397–405, https://doi.org/10.1016/j.biocon.2005.01.044

52 van der Ree R., van der Grift E., Mata C. & Suarez F. (2007) Overcoming the barrier effect of roads — how effective are mitigation strategies? An international review of the use and effectiveness of underpasses and overpasses designed to increase the permeability of roads for wildlife. Proceedings of the International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 423–431.

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54 Goldingay R.L., Taylor B.D. & Ball T. (2011) Wooden poles can provide habitat connectivity for a gliding mammal. Australian Mammalogy, 33, 36–43, https://doi.org/10.1071/am10023

55 Bond A.R. & Jones N.J. (2008) Temporal trends in use of fauna-friendly underpasses and overpasses. Wildlife Research, 35, 103–112, https://doi.orgdoi.org/10.1071/wr07027

56 Mata C., Hervàs I., Herranz J., Suàrez F. & Malo J.E. (2008) Are motorway passages worth building? Vertebrate use of road-crossing structures on a Spanish motorway. Journal of Environmental Management, 88, 407–415, https://doi.org/10.1016/j.jenvman.2007.03.014

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60 Klar N., Herrmann M. & Kramer-Schadt S. (2009) Effects and mitigation of road impacts on individual movement behavior of wildcats. The Journal of Wildlife Management, 73, 631–638, https://doi.org/10.2193/2007-574

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62 Rodriguez A., Crema G. & Delibes M. (1996) Use of non-wildlife passages across a high speed railway by terrestrial vertebrates. Journal of Applied Ecology, 33, 1527–1540, https://doi.org/10.2307/2404791

63 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicle collisions. Wildlife Society Bulletin, 29, 646– 653, https://doi.org/10.2307/3784191

64 Doucet G.J., Sarrazin J. & Bider J-P.R. & Bider R. (1974) Use of highway overpass embankments by the woodchuck, Marmota monax. The Canadian Field-Naturalist, 88, 187–190.

65 Taylor B.D. & Goldingay R.L. (2010) Roads and wildlife: impacts, mitigation and implications for wildlife management in Australia. Wildlife Research, 37, 320–331, https://doi.org/10.1071/wr09171

66 Sawaya M.A., Clevenger A.P. & Kalinowski S.T. (2013) Demographic connectivity for ursid populations at wildlife crossing structures in Banff National Park. Conservation Biology, 27, 721–730, https://doi.org/10.1111/cobi.12075

67 Bond A.R. & Jones D.N. (2014) Roads and macropods: interactions and implications. Australian Mammalogy, 36, 1–14, https://doi.org/10.1071/am13005

68 D’Amico M., Clevenger A.P., Román J. & Revilla E. (2015) General versus specific surveys: Estimating the suitability of different road-crossing structures for small mammals. The Journal of Wildlife Management, 79, 854– 860, https://doi.org/10.1002/jwmg.900

69 Simpson N.O., Stewart K.M., Schroeder C., Cox M., Huebner K. & Wasley, T. (2016) Overpasses and underpasses: Effectiveness of crossing structures for migratory ungulates. The Journal of Wildlife Management, 80, 1370–1378, https://doi.org/10.1002/jwmg.21132

70 Ford A.T., Barrueto M. & Clevenger A.P. (2017) Road mitigation is a demographic filter for grizzly bears. Wildlife Society Bulletin, 41, 712–719, https://doi.org/10.1002/wsb.828

71 Goldingay R.L., Taylor B.D. & Ball T. (2011) Wooden poles can provide habitat connectivity for a gliding mammal. Australian Mammalogy, 33, 36–43, https://doi.org/10.1071/am10023

72 Taylor B.D. & Goldingay R.L. (2012) Restoring connectivity in landscapes fragmented by major roads: a case study using wooden poles as ‘stepping stones’ for gliding mammals. Restoration Ecology, 20, 671–678, https://doi.orgdoi.org/10.1111/j.1526-100x.2011.00847.x

73 Kelly C.A., Diggins C.A. & Lawrence A.J. (2013) Crossing structures reconnect federally endangered flying squirrel populations divided for 20 years by road barrier. Wildlife Society Bulletin, 37, 375–379, https://doi.orgdoi.org/10.1002/wsb.249

74 Soanes K., Lobo M.C., Vesk P.A., McCarthy M.A., Moore J.L. & van der Ree R. (2013) Movement re-established but not restored: Inferring the effectiveness of road-crossing mitigation for a gliding mammal by monitoring use. Biological Conservation, 159, 434–441, https://doi.org/10.1016/j.biocon.2012.10.016

75 Taylor B.D. & Goldingay R.L. (2013) Squirrel gliders use roadside glide poles to cross a road gap. Australian Mammalogy, 35, 119–122, https://doi.orgdoi.org/10.1071/am12013

76 Soanes K., Vesk P.A. & van der Ree R. (2015) Monitoring the use of road-crossing structures by arboreal marsupials: insights gained from motion-triggered cameras and passive integrated transponder (PIT) tags. Wildlife Research, 42, 241–256, https://doi.org/10.1071/wr14067

77 Soanes K., Mitchell B. & van der Ree R. (2017) Quantifying predation attempts on arboreal marsupials using wildlife crossing structures above a major road. Australian Mammalogy, 39, 254–257, https://doi.org/10.1071/am16044

78 Goosem M., Weston N. & Bushnell S. (2005) Effectiveness of rope bridge arboreal overpasses and faunal underpasses in providing connectivity for rainforest fauna. Proceedings of the International Conference on Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 304–318.

79 Weston N., Goosem M., Marsh H., Cohen M. & Wilson R. (2011) Using canopy bridges to link habitat for arboreal mammals: successful trials in the Wet Tropics of Queensland. Australian Mammalogy, 33, 93–105, https://doi.orgdoi.org/10.1071/am11003

80 Taylor B.D. & Goldingay R.L. (2012) Restoring connectivity in landscapes fragmented by major roads: a case study using wooden poles as ‘stepping stones’ for gliding mammals. Restoration Ecology, 20, 671–678, https://doi.orgdoi.org/10.1111/j.1526-100x.2011.00847.x

81 Goldingay R.L., Rohweder D. & Taylor B.D. (2013) Will arboreal mammals use rope-bridges across a highway in eastern Australia? Australian Mammalogy, 35, 30–38, https://doi.org/10.1071/am12006

82 Soanes K., Lobo M.C., Vesk P.A., McCarthy M.A., Moore J.L. & van der Ree R. (2013) Movement re-established but not restored: Inferring the effectiveness of road-crossing mitigation for a gliding mammal by monitoring use. Biological Conservation, 159, 434–441, https://doi.org/10.1016/j.biocon.2012.10.016

83 Teixeira F.Z., Printes R.C., Fagundes J.C.G., Alonso A.C. & Kindel A. (2013) Canopy bridges as road overpasses for wildlife in urban fragmented landscapes. Biota Neotropica, 13, 117–123, https://doi.org/10.1590/s1676-06032013000100013

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85 Goldingay R.L. & Taylor B.D. (2017) Targeted field testing of wildlife road-crossing structures: koalas and canopy rope-bridges. Australian Mammalogy, 39, 100–104, https://doi.org/10.1071/am16014

86 Gregory T., Carrasco-Rueda F., Alonso A., Kolowski J. & Deichmann J.L. (2017) Natural canopy bridges effectively mitigate tropical forest fragmentation for arboreal mammals. Scientific Reports, 7, 3892, https://doi.orgdoi.org/10.1038/s41598-017-04112-x

87 Soanes K., Mitchell B. & van der Ree R. (2017) Quantifying predation attempts on arboreal marsupials using wildlife crossing structures above a major road. Australian Mammalogy, 39, 254–257, https://doi.org/10.1071/am16044

88 Reed D.F., Pojar T.M. & Woodard T.N. (1974) Use of one-way gates by mule deer. The Journal of Wildlife Management, 38, 9–15, https://doi.orgdoi.org/10.2307/3800194

89 Reed D.F., Beck T.D.I. & Woodward T.N. (1982) Methods of reducing deer– vehicle accidents: benefit–cost analysis. Wildlife Society Bulletin, 10, 349–354.

90 Ludwig J. & Bremicker T. (1983) Evaluation of 2.4 m fences and one-way gates for reducing deer vehicle collisions in Minnesota. Transportation Research Record, 913, 19–22.

91 McDonald M.G. (1991) Moose movement and mortality associated with the Glenn Highway expansion. Alces, 27, 208–219.

92 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing deer-vehicle collisions. Wildlife Society Bulletin, 25, 809–818.

93 Bissonette J. & Hammer M. (2000) Comparing the effectiveness of earthen escape ramps with one-way gates in Utah. USGS Utah cooperative Fish and Wildlife Research Unit, Logan, Utah.

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96 Reed D.F., Beck T.D.I. & Woodward T.N. (1982) Methods of reducing deer– vehicle accidents: benefit–cost analysis. Wildlife Society Bulletin, 10, 349–354.

97 Ludwig J. & Bremicker T. (1983) Evaluation of 2.4 m fences and one-way gates for reducing deer vehicle collisions in Minnesota. Transportation Research Record, 913, 19–22.

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99 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing deer-vehicle collisions. Wildlife Society Bulletin, 25, 809–818, https://doi.org/10.2307/3808706

100 Dodd C.K., Barichivich W.J. & Smith L.L. (2004) Effectiveness of a barrier wall and culverts in reducing wildlife mortality on a heavily travelled highway in Florida. Biological Conservation, 118, 619–631, https://doi.org/10.1016/j.biocon.2003.10.011

101 Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Electric fencing as a measure to reduce moose–vehicle collisions. The Journal of Wildlife Management, 71, 1695–1703, https://doi.org/10.2193/2006-375

102 Klar N., Herrmann M. & Kramer-Schadt S. (2009) Effects and mitigation of road impacts on individual movement behavior of wildcats. The Journal of Wildlife Management, 73, 631–638, https://doi.org/10.2193/2007-574

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104 Stull D.W., Gulsby W.D., Martin J.A., D’Angelo G.J., Gallagher G.R., Osborn D.A., Warren R.J. & Miller K.V. (2011) Comparison of fencing designs for excluding deer from roadways. Human-Wildlife Interactions, 5, 47–57.

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109 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyoming. Transportation Research Record, 859. 8–13.

110 Singer F.J. & Doherty J.L. (1985) Managing mountain goats at a highway crossing. Wildlife Society Bulletin, 13, 469–477.

111 McDonald M.G. (1991) Moose movement and mortality associated with the Glenn Highway expansion. Alces, 27, 208–219.

112 Foster M.L. & Humphrey S.R. (1995) Use of highway underpasses by Florida panthers and other wildlife. Wildlife Society Bulletin, 23, 95–100.

113 Land D. & Lotz M. (1996) Wildlife crossing designs and use by Florida panthers and other wildlife in southwest Florida. Proceedings -Trends in addressing wildlife mortality: transportation related wildlife mortality seminar, Florida Department of Transportation, Tallahassee, Florida USA, 379–386.

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127 Plumb R.E., Gordon K.M. & Anderson S.H. (2003) Pronghorn use of a wildlife underpass. Wildlife Society Bulletin, 31, 1244–1245, https://doi.orgdoi.org/10.2307/3784474

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130 Dodd C.K., Barichivich W.J. & Smith L.L. (2004) Effectiveness of a barrier wall and culverts in reducing wildlife mortality on a heavily traveled highway in Florida. Biological Conservation, 118, 619–631, https://doi.org/10.1016/j.biocon.2003.10.011

131 Dodd N.I., Gagnon J.W., Manzo A.I. & Schweinsburg R.E. (2007) Video surveillance to assess highway underpass use by elk in Arizona. The Journal of Wildlife Management, 71, 637–-645, https://doi.org/10.2193/2006-340

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135 Clevenger A.P. & Waltho N. (2005) Performance indices to identify attributes of highway crossing structures facilitating movement of large mammals. Biodiversity and Conservation, 121, 453–464, https://doi.org/10.1016/j.biocon.2004.04.025

136 Gagnon J.W., Dodd N.L., Ogren K.S. & Schweinsburg R.E. (2011) Factors associated with use of wildlife underpasses and importance of long-term monitoring. The Journal of Wildlife Management, 75, 1477–1487, https://doi.orgdoi.org/10.1002/jwmg.160

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138 Dodd N.I., Gagnon J.W., Manzo A.I. & Schweinsburg R.E. (2007) Video surveillance to assess highway underpass use by elk in Arizona. The Journal of Wildlife Management, 71, 637–-645, https://doi.org/10.2193/2006-340

139 Ascensão F. & Mira A. (2007) Factors affecting culvert use by vertebrates along two stretches of road in southern Portugal. Ecological Research, 22, 57–66, https://doi.org/10.1007/s11284-006-0004-1

140 Baker A., Knowles M. & Latham D. (2007) Using clay drain seals to assess the use of dry culverts installed to allow mammals to pass under the A1 trunk road, Northumberland, England. Conservation Evidence, 4, 77–80

141 Leblond M., Dussault C., Ouellet J.-P., Poulin M., Courtois R. & Fortin J. (2007) Electric fencing as a measure to reduce moose–vehicle collisions. The Journal of Wildlife Management, 71, 1695–1703, https://doi.org/10.2193/2006-375

142 Bond A.R. & Jones N.J. (2008) Temporal trends in use of fauna-friendly underpasses and overpasses. Wildlife Research, 35, 103–112, https://doi.orgdoi.org/10.1071/WR07027

143 Gordon K.M. & Anderson S.H. (2003) Mule deer use of underpasses in western and southeastern Wyoming. Proceedings -International Conference on Wildlife Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 309–318.

144 Dodd N.L., Gagon J.W. & Schweinsburg R.E. (2003) Evaluation of measures to minimize wildlife-vehicle collisions and maintain wildlife permeability across highways in Arizona, USA. Proceedings -International Conference on Wildlife Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 353–354.

145 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyoming. Transportation Research Record, 859. 8–13.

146 Reed D.F. (1981) Mule deer behavior at a highway underpass exit. The Journal of Wildlife Management, 45, 542–543.

147 Braden A.W., Lopez R.R., Roberts C.W., Silvy N.J., Owen C.B. & Frank P.A. (2008) Florida Key deer Odocoileus virginianus clavium underpass use and movements along a highway corridor. Wildlife Biology, 14, 155–163, https://doi.org/10.2981/0909-6396(2008)14[155:FKDOVC]2.0.CO;2

148 Grilo C., Bissonette J.A., and Santos-Reis M. (2008) Response of carnivores to existing highway culverts and underpasses: implications for road planning and mitigation. Biodiversity Conservation, 17, 1685–1699.

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153 Hayes I. & Goldingay R.L. (2009) Use of fauna road-crossing structures in north-eastern New South Wales. Australian Mammalogy, 31, 89–95, https://doi.org/10.1071/AM09007

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156 Mathiasen R. & Madsen A.B. (2000) Infrared video-monitoring of mammals at a fauna underpass. International Journal of Mammalian Biology, 65, 59–61.

157 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass. The Journal of Wildlife Management, 39, 361–367, https://doi.org/10.2307/3799915

158 Singer F.J. & Doherty J.L. (1985) Managing mountain goats at a highway crossing. Wildlife Society Bulletin, 13, 469–477.

159 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass. The Journal of Wildlife Management, 39, 361–367, https://doi.org/10.2307/3799915

160 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass. The Journal of Wildlife Management, 39, 361–367, https://doi.org/10.2307/3799915

161 McCollister M.F. & van Manen F.T. (2010) Effectiveness of wildlife underpasses and fencing to reduce wildlife-vehicle collisions. The Journal of Wildlife Management, 74, 1722–1731, https://doi.org/10.2193/2009-535

162 Brudin C.O. (2003) Wildlife use of existing culverts and bridges in north central Pennsylvania. Proceedings -International Conference on Wildlife Ecology and Transportation, Center for Transportation and the Environment, North Carolina State University, Raleigh NC, USA, 334–352.

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165 Dodd N.L., & Gagnon J.W. (2011) Influence of underpasses and traffic on white-tailed deer highway permeability. Wildlife Society Bulletin, 35, 270–281, https://doi.org/10.1002/wsb.31

166 Eldridge B. & Wynn J. (2011) Use of badger tunnels on Highway Agency schemes in England. Conservation Evidence, 8, 53–57.

167 Gagnon J.W., Dodd N.L., Ogren K.S. & Schweinsburg R.E. (2011) Factors associated with use of wildlife underpasses and importance of long-term monitoring. The Journal of Wildlife Management, 75, 1477–1487, https://doi.orgdoi.org/10.1002/jwmg.160

168 Parker I.D., Lopez R.R., Silvy N.J., Davis D.S. & Owen C.B. (2011) Long-term effectiveness of US 1 crossing project in reducing Florida Key deer mortality. Wildlife Society Bulletin, 35, 296–302, https://doi.org/10.1002/wsb.45

169 Sawyer H., Lebeau C. & Hart T. (2012) Mitigating roadway impacts to migratory mule deer—a case study with underpasses and continuous fencing. Wildlife Society Bulletin, 36, 492–498, https://doi.org/10.1002/wsb.166

170 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicle collisions. Wildlife Society Bulletin, 29, 646– 653, https://doi.org/10.2307/3784191

171 Clevenger A.P. (1998) Permeability of the Trans-Canada highway to wildlife in Banff National Park: importance of crossing structures and factors influencing their effectiveness. Proceedings-International Conference on Wildlife Ecology and Transportation, Florida Department of Transportation, Tallahassee, Florida, USA, 109–119.

172 Clevenger A.P., Chruszcz B. & Gunson K.E. (2001) Highway mitigation fencing reduces wildlife-vehicle collisions. Wildlife Society Bulletin, 29, 646– 653, https://doi.org/10.2307/3784191

173 Ward A.L. (1982) Mule deer behavior in relation to fencing and underpasses on Interstate 80 in Wyoming. Transportation Research Record, 859. 8–13.

174 Reed D.F., Woodard T.N. & Pojar T.M. (1975) Behavioral response of mule deer to a highway underpass. The Journal of Wildlife Management, 39, 361–367, https://doi.org/10.2307/3799915

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179 Chambers B. & Bencini R. (2015) Factors affecting the use of fauna underpasses by bandicoots and bobtail lizards. Animal Conservation, 18, 424–432, https://doi.org/10.1111/acv.12189

180 Murphy-Mariscal M.L., Barrows C.W. & Allen M.F. (2015) Native wildlife use of highway underpasses in a desert environment. The Southwestern Naturalist, 60, 340–348, https://doi.org/10.1894/0038-4909-60.4.340

181 Huijser M.P., Fairbank E.R., Camel-Means W., Graham J., Watson V., Basting P. & Becker D. (2016) Effectiveness of short sections of wildlife fencing and crossing structures along highways in reducing wildlife–vehicle collisions and providing safe crossing opportunities for large mammals. Biological Conservation, 197, 61–68, https://doi.org/10.1016/j.biocon.2016.02.002

182 Huijser M.P., Fairbank E.R., Camel-Means W., Graham J., Watson V., Basting P. & Becker D. (2016) Effectiveness of short sections of wildlife fencing and crossing structures along highways in reducing wildlife–vehicle collisions and providing safe crossing opportunities for large mammals. Biological Conservation, 197, 61–68, https://doi.org/10.1016/j.biocon.2016.02.002

183 Simpson N.O., Stewart K.M., Schroeder C., Cox M., Huebner K. & Wasley, T. (2016) Overpasses and underpasses: Effectiveness of crossing structures for migratory ungulates. The Journal of Wildlife Management, 80, 1370–1378, https://doi.org/10.1002/jwmg.21132

184 Ford A.T., Barrueto M. & Clevenger A.P. (2017) Road mitigation is a demographic filter for grizzly bears. Wildlife Society Bulletin, 41, 712–719, https://doi.org/10.1002/wsb.828

185 Andreassen H.P., Gundersen H. & Storaas T. (2005) The effect of scent-marking, forest clearing, and supplemental feeding on moose-train collisions. The Journal of Wildlife Management, 69, 1125–1132, https://doi.orgdoi.org/10.2193/0022-541x(2005)069[1125:teosfc]2.0.co;2

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196 D’Angelo G.J., D’Angelo J.G., Gallagher G.R., Osborn D.A., Miller K.V. & Warren R.J. (2006) Evaluation of wildlife warning reflectors for altering white-tailed deer behavior along roadways. Wildlife Society Bulletin, 34, 1175– 1183, https://doi.org/10.2193/0091-7648(2006)34[1175:eowwrf]2.0.co;2

197 Ramp D. & Croft D.B. (2006) Do wildlife warning reflectors elicit aversion in captive macropods? Wildlife Research, 33, 583–590, https://doi.org/10.1071/wr05115

198 Bond A.R. & Jones D.N. (2014) Roads and macropods: interactions and implications. Australian Mammalogy, 36, 1–14, https://doi.org/10.1071/am13005

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203 Lehnert M.E. & Bissonette J.A. (1997) Effectiveness of highway crosswalk structures at reducing deer-vehicle collisions. Wildlife Society Bulletin, 25, 809–818.

204 Reed D.F., Pojar T.M. & Woodard T.N. (1974) Mule deer responses to deer guards. Journal of Range Management, 27, 111–113.

205 Peterson M.N., Lopez R.P., Silvy N.J., Owen C.B., Frank P.A. & Braden A.W. (2003) Evaluation of deer-exclusion grates in urban areas. Wildlife Society Bulletin, 31, 1198–1204.

206 Allen T.D., Huijser M.P. & Willey D.W. (2013) Effectiveness of wildlife guards at access roads. Wildlife Society Bulletin, 37, 402–408, https://doi.orgdoi.org/10.1002/wsb.253

207 Bertwistle J. (1999) The effects of reduced speed zones on reducing bighorn sheep and elk collisions with vehicles on the Yellowhead Highway in Jasper National Park. Proceedings -Third International Conference on Wildlife Ecology and Transportation. Tallahassee, Florida, USA, 89–97.

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210 Jaren V., Andersen R., Ulleberg M., Pedersen P.H. & Wiseth B. (1991) Moose-train collisions: the effects of vegetation removal with a cost–benefit analysis. Alces, 27, 93–99.

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212 Romin L.A. & Dalton L.B. (1992) Lack of response by mule deer to wildlife warning whistles. Wildlife Society Bulletin, 20, 382–384.

213 Bender H. (2001) Deterrence of kangaroos from roadways using ultrasonic frequencies: efficacy of the Shu Roo. University of Melbourne, Department of Zoology unpublished report.

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218 Sullivan T.L., Williams A.F., Messmer T.A., Hellinga L.A. & Kyrychenko S.Y. (2004) Effectiveness of temporary warning signs in reducing deer-vehicle collisions during mule deer migrations. Wildlife Society Bulletin, 32, 907–915, https://doi.org/10.2193/0091-7648(2004)032[0907:eotwsi]2.0.co;2

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