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What Works in Conservation 2021

 | 
William Junior Sutherland
, 
Lynn V. Dicks
, 
Silviu O. Petrovan
, 
et al.

15. Terrestrial mammal conservation

15.13 Species management

Texte intégral

15.13.1 Translocate mammals

Beneficial

Release translocated mammals into fenced areas

1Twenty-four studies evaluated the effects of releasing translocated mammals into fenced areas. Nine studies were in Australia, six studies were in South Africa, two studies were in the USA and one study was in each of India, China, Spain, Hungary, Namibia and South Africa and France.

2COMMUNITY RESPONSE (0 STUDIES)

3POPULATION RESPONSE (22 STUDIES)

4Abundance (5 studies): Five studies (one replicated) in the USA, Australia and South Africa found that following translocation into fenced areas, 18 African elephant populations, tule elk, brushtail possum and elk and bison increased in number and following eradiation of invasive species a population of translocated and released captive-bred burrowing bettongs increased. A replicated, controlled study in Spain found that the abundance of translocated European rabbits was higher in areas fenced to exclude predators than unfenced areas.

5Reproductive success (7 studies): Two replicated, controlled studies in France and Spain found that after translocation, reproductive success of common hamsters and European rabbits was higher inside than outside fenced areas or warrens. Four studies (one replicated, controlled) in China and South Africa found that following translocation into a fenced area, Père David’s deer, lions, translocated and captive-bred African wild dogs and one of two groups of Cape buffalo reproduced. A study in Australia found that four of five mammal populations released into a predator-free enclosure and one population released into a predator-reduced enclosure reproduced, whereas two populations released into an unfenced area with ongoing predator management did not survive to breed.

6Survival (13 studies): Two replicated, controlled studies in Spain and France found that after translocation, survival rates of common hamsters and European rabbits were higher inside than outside fenced areas or warrens. A study in Australia found that four of five mammal populations released into a predator-free enclosure and one population released into a predator-reduced enclosure survived, whereas two populations released into an unfenced area with ongoing predator management did not persist. Five studies in India, China, South Africa, Namibia and South Africa and Australia found that following translocation into fenced areas, most black rhinoceroses and greater Indian rhinoceroses, Père David’s deer, most oribi and offspring of translocated golden bandicoots survived for between one and 10 years. Two studies in Australia found that only two of five translocated numbats survived over seven months and western barred bandicoots did not persist. A study in South Africa found that translocated and captive-bred African wild dogs released into fenced reserves in family groups had high survival rates. A study in Australia found that following release into fenced areas, a translocated population of red-tailed phascogales survived longer than a released captive-bred population. A replicated, controlled study in South Africa found that after translocation to a fenced reserve with holding pens, survival of released lions was higher than that of resident lions.

7Condition (3 studies): A replicated, before-and-after study in Australia found that eastern bettongs translocated into fenced predator proof enclosures increased in body weight post-release, with and without supplementary food. A replicated study in South Africa found that following translocation into fenced reserves, stress hormone levels of African elephants declined over time. A study in Australia found that golden bandicoots descended from a population translocated into a fenced area free from non-native predators, maintained genetic diversity relative to the founder and source populations. BEHAVIOUR (2 STUDIES)

8Use (2 studies): A site comparison study in Australia found that following translocation into a predator-free fenced area, woylies developed home ranges similar in size to those of an established population outside the enclosure. A study in Hungary found that one fifth of translocated European ground squirrels released into a fenced area with artificial burrows remained in the area after release.

9Assessment: beneficial (effectiveness 80 %; certainty 70 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2467

Translocate to re-establish or boost populations in native range

10Sixty-four studies evaluated the effects of translocating mammals to re-establish or boost populations in their native range. Twenty studies were in the USA, eight in Italy, four in Canada and South Africa, three in the Netherlands and Spain, two in each of the USA and Canada, Zimbabwe, Sweden, Australia and the USA and Mexico and one in each of Uganda, the UK, Brazil, France, Portugal, Africa, Europe, North America, Botswana, Nepal, Chile, Slovakia, Ukraine, Slovakia and Poland and one global study.

11COMMUNITY RESPONSE (0 STUDIES)

12POPULATION RESPONSE (62 STUDIES)

13Abundance (22 studies): Two studies (incuding one controlled and one before-and-after, site comparison study) in Spain and Canada found that translocating animals increased European rabbit abundance or American badger population growth rate at release sites. Fourteen studies (one replicated) in South Africa, the USA, the Netherlands, Italy, France and Spain found that following translocation, populations of warthogs, Eurasian beavers, red squirrels, roe deer, Alpine ibex, Iberian ibex, Cape mountain zebra, 22 species of grazing mammals, black bears, brown bear, bobcats and most populations of river otters increased. Two reviews in South Africa and Australia found that reintroductions (mainly through translocations) led to increasing populations for four of six species of large carnivores and that over half of translocations were classified as successful. One replicated study in the USA and Mexico found that translocating desert bighorn sheep did not increase the population size. Two studies (one replicated) and a review in USA and Canada, the USA and Australia found that translocated American martens, and sea otters at four of seven sites, established populations and that translocated and released captive-bred macropod species established populations in 44 of 72 cases. A study in Italy found that following the translocation of red deer, the density of Apennine chamois in the area almost halved. A worldwide review found that translocating ungulates was more successful when larger numbers were released, and small populations grew faster if they contained more mature individuals and had an equal ratio of males and females.

14Reproductive success (16 studies): A controlled study in Italy found that wild-caught translocated Apennine chamois reproduced in similar numbers to released captive-bred chamois. Fourteen studies (four replicated) in Canada, the USA, Zimbabwe, South Africa, the UK, Italy, the Netherlands and Slovakia found that translocated black and white rhinoceroses, warthogs, common dormice, European ground squirrels, cougars, bobcats, brown bears, sea otters, river otters and some Eurasian otters reproduced. A study in the Netherlands found that translocated beavers were slow to breed.

15Survival (39 studies): Four of five studies (including three controlled, two replicated and one before-and-after, site comparison study) in the USA, Canada and Chile found that wild-born translocated long-haired field mice, female elk, cougars and American badgers had lower survival rates than non-translocated resident animals. One found that translocated Lower Keys marsh rabbits had similar survival rates to non-translocated resident animals. Five of four studies (two replicated, four controlled) and two reviews in Canada, Canada and the USA, the USA, Italy, Sweden and Africa, Europe, and North America found that wild-born translocated swift foxes, European otters, black-footed ferret kits and a mix of carnivores had higher survival rates than released captive-bred animals. One study found that wild-born translocated Apennine chamois had a similar survival rate to released captive-bred animals. Twenty of twenty-one studies (including two replicated and one before-and-after study) and a review in Nepal, France, Italy, Portugal, Ukraine, Slovakia and Poland, Canada, USA, Brazil, Uganda, South Africa, Zimbabwe and Botswana found that following translocation, populations of or individual mammals survived between two months and at least 25 years. The other two studies found that two of 10 translocated white rhinoceroses died within three days of release and an American marten population did not persist. A review in Australia found that over half of translocations, for which the outcome could be determined, were classified as successful. Two of three studies (one replicated) and one review in Sweden, the UK, the Netherlands and the USA and Mexico found that following release of wild-caught translocated and captive-bred animals, European otters and common dormice survived three months to seven years. The review found that most black-footed ferret releases were unsuccessful at maintaining a population. A replicated study in the USA found that following translocation of bighorn sheep, 48–98 % of their offspring survived into their first winter.

16Condition (3 studies): Three studies (including one replicated, controlled study) in the USA and Italy found that following translocation, populations of elk had similar levels of genetic diversity to non-translocated populations, descendants of translocated swift fox had genetic diversity at least as high as that of the translocated animals and brown bear genetic diversity declined over time.

17BEHAVIOUR (9 STUDIES)

18Use (7 studies): A study in Italy found that following translocation, Alpine ibex used similar habitats to resident animals. Two of four studies (including one randomized, controlled study) in the USA, Netherlands and Botswana found that following translocation (and in one case release of some captive-bred animals), most Eurasian otters settled and all three female grizzly bears established ranges at their release site. The other two studies found that most nine-banded armadillos and some white rhinoceroses (when released into areas already occupied by released animals) dispersed from their release site. Two studies (one replicated) in Spain found that following translocation, Iberian ibex expanded their range and roe deer increased their distribution six-fold. Behaviour change (2 studies): A replicated controlled study in Chile found that following translocation, long-haired field mice travelled two- to four-times further than non-translocated mice. A controlled study in Italy found that wild-caught translocated Apennine chamois moved further from the release site than released captive-bred animals.

19Assessment: beneficial (effectiveness 75 %; certainty 70 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2397

Likely to be beneficial

Hold translocated mammals in captivity before release

20Fifteen studies evaluated the effects of holding translocated mammals in captivity before release. Four studies were in the USA, two were in Australia and one was in each of India, Canada, Switzerland, Croatia and Slovenia, the USA and Canada, the UK, France, Spain and South Africa.

21COMMUNITY RESPONSE (0 STUDIES)

22POPULATION RESPONSE (13 STUDIES)

23Abundance (2 studies): Two studies (one replicated, before-and-after study) in Croatia and Slovenia and the USA found that following translocation, with time in captivity prior to release, Eurasian lynx established an increasing population and Allegheny woodrat numbers in four of six sites increased over the first two years.

24Reproductive success (4 studies): Four studies in Croatia and Slovenia, Spain, the USA and Canada and Australia found that following translocation, with time in captivity prior to release, Eurasian lynx established a breeding population, and swift foxes, European otters and red-tailed phascogales reproduced.

25Survival (10 studies): Two studies (one controlled) in the UK and USA found that being held for longer in captivity before release increased survival rates of translocated European hedgehogs and, along with release in spring increased the survival rate of translocated Canada lynx in the first year. Four of six studies in India, the USA and Canada, the USA, France, South Africa and Australia found that following translocation, with time in captivity prior to release, most swift foxes and greater Indian rhinoceroses survived for at least 12-20 months, 48 % of Eurasian lynx survived for 2–11 years and red-tailed phascogales survived for at least six years. The other two studies found that most kangaroo rats and all rock hyraxes died within 5-87 days. A replicated, controlled study in Canada found that translocated swift foxes that had been held in captivity prior to release had higher post-release survival rates than did released captive-bred animals.

26Condition (3 studies): A randomised, controlled study in Australia found that holding translocated eastern bettongs in captivity before release did not increase their body mass after release compared to animals released directly into the wild. A controlled study the UK found that being held for longer in captivity before release, reduced weight loss after release in translocated European hedgehogs. A study in Spain found that offspring of translocated European otters that were held in captivity before release, had similar genetic diversity to donor populations.

27Occupancy/range (2 studies): A study in the USA found that most translocated and captive-bred mountain lions that had been held in captivity prior to release established home ranges in the release area. A study in Croatia and Slovenia and review in Switzerland found that following translocation, with time in captivity prior to release, the range of Eurasian lynx increased over time. BEHAVIOUR (0 STUDIES)

28Assessment: likely to be beneficial (effectiveness 60 %; certainty 60 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2458

Provide supplementary food during/after release of translocated mammals

29Sixteen studies evaluated the effects of providing supplementary food during/ after release of translocated mammals. Four studies were in the UK, two were in each of the USA, France, Australia and Argentina, and one was in each of Italy, Spain, Ireland and South Africa.

30COMMUNITY RESPONSE (0 STUDIES)

31POPULATION RESPONSE (15 STUDIES)

32Abundance (2 studies): A controlled study in Spain found that providing supplementary food during translocation did not increase European rabbit abundance. A study in France found that following supplementary feeding in a holding pen prior to release, a translocated deer population increased over six years.

33Reproductive success (4 studies): Three studies (one replicated) in the USA, Italy and Ireland found that having been provided with supplementary food in holding pens prior to release, translocated black-tailed prairie dogs, a pair of Eurasian badgers and most female red squirrels reproduced in the wild. A study in the UK found that some translocated pine martens released from holding pens and then provided with supplementary food and nest boxes bred in the first year after release.

34Survival (10 studies): Six of 10 studies (including one replicated and one controlled study) in the UK, France, Italy, Ireland, South Africa, USA, Argentina and Australia found that at sites with supplementary food in holding pens before (and in two cases after) release, translocated populations of black-tailed prairie dogs, approximately half of female roe deer and over half of red squirrels, Eurasian badgers, pine martens and released rehabilitated or captive reared giant anteaters survived for between one month and at least two years. Four studies found that at translocation release sites with provision of supplementary food, in most cases artificial refuges and in one case water, no red squirrels, rock hyraxes or burrowing bettongs survived over 2-5 months and most translocated Tipton and Heermann’s kangaroo rat spp. died within five days. A controlled study in France found that translocated European rabbits provided with supplementary food in holding pens for three days prior to release had higher female (but not male) survival rates immediately following release compared to those released directly. A controlled study in the UK found that survival of translocated and rehabilitated European hedgehogs that were provided with supplementary food after release varied with release method.

35Condition (2 studies): One of three studies (including one replicated, one controlled and two before-and-after studies) in the UK and Australia found that translocated common dormice gained weight after being provided with supplementary food. One found that translocated eastern bettongs did not have increased body weights after provision of supplementary food in fenced enclosures prior to release. The other found that translocated and rehabilitated European hedgehogs provided with food after release all lost body mass, with effects varying with release method.

36BEHAVIOUR (2 STUDIES)

37Use (1 study): A controlled study in Australia found that supplementary feeding stations were visited by translocated burrowing bettongs.

38Behaviour change (1 study): A controlled study in Argentina found that after being provided with supplementary food and kept in holding pens, released captive-bred giant anteaters were less nocturnal than wild-born rehabilitated and released individuals.

39Assessment: likely to be beneficial (effectiveness 67 %; certainty 60 %; harms 0 %).

40https://www.conservationevidence.com/​actions/​2470

Translocate predators for ecosystem restoration

41Two studies evaluated the effects of translocating predators for ecosystem restoration. These studies were in the USA.

42COMMUNITY RESPONSE (0 STUDIES)

43POPULATION RESPONSE (2 STUDIES)

44Abundance (2 studies): A before-and-after study in the USA found that following reintroduction of wolves, populations of beavers and bison increased. A before-and-after study in the USA found that after the translocation of wolves to the reserve, adult elk numbers approximately halved.

45Reproductive success (1 study): A before-and-after study in the USA found that after the translocation of wolves to the reserve, elk calf: cow ratios approximately halved.

46BEHAVIOUR (0 STUDIES)

47Assessment: likely to be beneficial (effectiveness 70 %; certainty 55 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2431

Use holding pens at release site prior to release of translocated mammals

48Thirty-five studies evaluated the effects of using holding pens at the release site prior to release of translocated mammals. Ten studies were in the USA, seven were in South Africa, four were in the UK, three studies were in France, two studies were in each of Canada, Australia and Spain and one was in each of Kenya, Zimbabwe, Italy, Ireland and India.

49COMMUNITY RESPONSE (0 STUDIES)

50POPULATION RESPONSE (31 STUDIES)

51Abundance (4 studies): Three of four studies (two replicated, one before-and-after study) in South Africa, Canada, France and Spain found that following release from holding pens at release sites (in some cases with other associated actions), populations of roe deer, European rabbits and lions increased in size. The other study found that elk numbers increased at two of four sites. Reproductive success (10 studies): A replicated study in the USA found that translocated gray wolves had similar breeding success in the first two years after release when adult family groups were released together from holding pens or when young adults were released directly into the wild. Seven of nine studies (including two replicated and one controlled study) in Kenya, South Africa, the USA, Italy, Ireland, Australia and the UK found that following release from holding pens at release sites (in some cases with other associated actions), translocated populations of roan, California ground squirrels, black-tailed prairie dogs, lions, four of four mammal populations, most female red squirrels and some pine martens reproduced successfully. Two studies found that one of two groups of Cape buffalo and one pair out of 18 Eurasian badgers reproduced.

52Survival (26 studies): Two of seven studies (five controlled, three replicated studies) in Canada, the USA, France, the UK found that releasing animals from holding pens at release sites (in some cases with associated actions) resulted in higher survival for water voles and female European rabbits compared to those released directly into the wild. Four studies found that translocated swift foxes, gray wolves, Eurasian lynx and Gunnison’s prairie dogs released from holding pens had similar survival rates to those released directly into the wild. One study found that translocated American martens released from holding pens had lower survival than those released directly into the wild. Two of four studies (three controlled) in South Africa, Spain, and the USA found that translocated African wild dogs and European rabbits that spent longer in holding pens at release sites had a higher survival rate after release. One study found mixed effects for swift foxes and one found no effect of time in holding pens for San Joaquin kit foxes. Eleven studies (one replicated) in Kenya, South Africa, the USA, France, Italy, Ireland, India, Australia and the UK found that after release from holding pens at release sites (in some cases with other associated actions), translocated populations or individuals survived between one month and six years, and four of four mammal populations survived. Two studies in the UK and South Africa found that no released red squirrels or rock hyraxes survived over five months or 18 days respectively. One of two controlled studies (one replicated, one before-and-after) in South Africa and the USA found that following release from holding pens, survival of translocated lions was higher than that of resident animals, whilst that of translocated San Joaquin kit foxes was lower than that of resident animals. A study in Australia found that translocated bridled nailtail wallabies kept in holding pens prior to release into areas where predators had been controlled had similar annual survival to that of captive-bred animals.

53Condition (1 study): A controlled study in the UK found that translocated common dormice held in pens before release gained weight after release whereas those released directly lost weight.

54BEHAVIOUR (5 STUDIES)

55Behaviour change (5 studies): Three studies (one replicated) in the USA and Canada found that following release from holding pens, fewer translocated sea otters and gray wolves returned to the capture site compared to those released immediately after translocation, and elk remained at all release sites. Two studies in Zimbabwe and South Africa found that following release from holding pens, translocated lions formed new prides.

56Assessment: likely to be beneficial (effectiveness 72 %; certainty 60 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2434

Trade-off between benefit and harms

Translocate mammals to reduce overpopulation

57Three studies evaluated the effects of translocating mammals to reduce overpopulation. Two studies were in the USA and one was in Australia.

58COMMUNITY RESPONSE (0 STUDIES)

59POPULATION RESPONSE (3 STUDIES)

60Abundance (1 study): A before-and-after study in the USA found that adult elk numbers approximately halved after the translocation of wolves to the reserve.

61Reproductive success (1 study): A before-and-after study in the USA found that elk calf: cow ratios approximately halved after the translocation of wolves to the reserve.

62Survival (2 studies): A study in Australia found that koalas translocated to reduce overpopulation had lower survival than individuals in the source population. A study in the USA found that following translocation to reduce over-abundance, white-tailed deer had lower survival rates compared to non-translocated deer at the recipient site.

63Occupancy/range (1 study): A study in the USA found that following translocation to reduce over-abundance at the source site, white-tailed deer had similar home range sizes compared to non-translocated deer at the recipient site.

64BEHAVIOUR (0 STUDIES)

65Assessment: trade-off between benefit and harms (effectiveness 66 %; certainty 47 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2430

Unknown effectiveness

Airborne translocation of mammals using parachutes

66One study evaluated the effects of airborne translocation of mammals using parachutes. This study was in the USA.

67COMMUNITY RESPONSE (0 STUDIES)

68POPULATION RESPONSE (1 STUDY)

69Survival (1 study): A study in the USA found that at least some North American beavers translocated using parachutes established territories and survived over one year after release.

70BEHAVIOUR (0 STUDIES)

71Assessment: unknown effectiveness (effectiveness 50 %; certainty 24 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2466

Use tranquilizers to reduce stress during translocation

72One study evaluated the effects on mammals of using tranquilizers to reduce stress during translocation. This study was in France.

73COMMUNITY RESPONSE (0 STUDIES)

74POPULATION RESPONSE (1 STUDY)

75Survival (1 study): A controlled study in France found that using tranquilizers to reduce stress during translocation did not increase post-release survival of European rabbits.

76BEHAVIOUR (0 STUDIES)

77Assessment: unknown effectiveness (effectiveness 10 %; certainty 15 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2465

15.13.2 Captive-breeding

Beneficial

Breed mammals in captivity

78Three studies evaluated the effects of breeding mammals in captivity. One study was across Europe, one was in the USA and one was global.

79COMMUNITY RESPONSE (0 STUDIES)

80POPULATION RESPONSE (3 STUDIES)

81Abundance (1 study): A review of captive-breeding programmes across the world found that the majority of 118 captive-bred mammal populations increased.

82Reproductive success (2 studies): A review of a captive breeding programme across Europe found that the number of European otters born in captivity tended to increase over 15 years. A study in the USA found that wild-caught Allegheny woodrats bred in captivity.

83Survival (1 study): A review of a captive breeding programme across Europe found that the number of European otters born in captivity that survived tended to increase over 15 years.

84BEHAVIOUR (0 STUDIES)

85Assessment: beneficial (effectiveness 80 %; certainty 70 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2471

Likely to be beneficial

Use artificial insemination

86Three studies evaluated the effects on mammals of using artificial insemination. One study was in the USA, one was in Brazil and one was in China.

87COMMUNITY RESPONSE (0 STUDIES)

88POPULATION RESPONSE (3 STUDIES)

89Reproductive success (3 studies): A study in the USA found that following artificial insemination, fewer than half of female black-footed ferrets gave birth. A study in Brazil found that following artificial insemination, a captive female Amazonian brown brocket deer gave birth. A replicated study in China found that following artificial insemination, a lower proportion of captive female giant pandas became pregnant than after natural mating.

90BEHAVIOUR (0 STUDIES)

91Assessment: likely to be beneficial (effectiveness 40 %; certainty 40 %; harms 9 %).

https://www.conservationevidence.com/​actions/​2473

Unknown effectiveness

Clone rare species

92One study evaluated the effects of cloning rare species. This study was in Iran. COMMUNITY RESPONSE (0 STUDIES)

93POPULATION RESPONSE (1 STUDY)

94Reproductive success (1 study): A controlled study in Iran found that immature eggs of domestic sheep have potential to be used for cloning of Esfahan mouflon.

95BEHAVIOUR (0 STUDIES)

96Assessment: unknown effectiveness (effectiveness 40 %; certainty 20 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2474

Place captive young with captive foster parents

97Two studies evaluated the effects of placing captive young mammals with captive foster parents. One study was in the USA and one was in Sweden and Norway.

98COMMUNITY RESPONSE (0 STUDIES)

99POPULATION RESPONSE (2 STUDIES)

100Survival (2 studies): A replicated, controlled study in the USA found that most captive coyote pups placed with foster parents were successfully reared. A replicated study in Sweden and Norway found that captive grey wolf pups placed with foster parents had higher survival rates than pups that stayed with their biological mother.

101Condition (1 study): A replicated study in Sweden and Norway found that captive grey wolf pups placed with foster parents weighed less than pups that stayed with their biological mother.

102BEHAVIOUR (0 STUDIES)

103Assessment: unknown effectiveness (effectiveness 70 %; certainty 32 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2472

Preserve genetic material for use in future captive breeding programs

104Two studies evaluated the effects of preserving genetic material for use in future captive breeding programs. One study was in Mexico and one was in the USA.

105COMMUNITY RESPONSE (0 STUDIES)

106POPULATION RESPONSE (2 STUDIES)

107Survival (2 studies): A study in Mexico found that a series of non-traditional techniques, combined with natural mating, produced five aoudad embryos that could be cryogenically preserved. A study in USA, found that artificial insemination using preserved genetic material increased genetic diversity and lowered inbreeding in a captive black-footed ferret population.

108BEHAVIOUR (0 STUDIES)

109Assessment: unknown effectiveness (effectiveness 60 %; certainty 35 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2475

15.13.3 Release captive-bred mammals

Beneficial

Provide supplementary food during/after release of captive-bred mammals

110Fifteen studies evaluated the effects of providing supplementary food during/ after release of captive-bred mammals. Four studies were in Australia, two were in each of the USA, China and Argentina, and one was in each of Poland, the UK, Oman and Saudi Arabia.

111COMMUNITY RESPONSE (0 STUDIES)

112POPULATION RESPONSE (14 STUDIES)

113Abundance (5 studies): Four studies (one replicated, one before-and-after study) and one review in Poland, Oman, China and Australia found that following provision of supplementary food (and in one case water) to released captive-bred animals, populations of European bison increased more than six-fold over 20 years, Arabian oryx increased over 14 years, eastern-barred bandicoots increased for the first five years before declining, Père David’s deer increased more than six-fold over 12 years and Przewalski’s horses (enclosed in winter) increased over 11 years.

114Reproductive success (9 studies): Eight studies (including two replicated and one before-and-after study) and one review in Poland, the UK, China, the USA, Australia and Saudi Arabia found that following the provision of supplementary food (and in one case water or artificial nests) after release of captive-bred animals, some from holding pens, European bison, European otters, Père David’s deer, eastern-barred bandicoots, Przewalski’s horses and some captive-bred red wolves successfully reproduced, Arabian gazelles started breeding in the year following releases and sugar gliders established a breeding population.

115Survival (6 studies): Four of six studies (one controlled, before-and-after study) in the UK, USA, Argentina and Australia found that following the provision of supplementary food (and in one case water or nest boxes) after release of captive-bred animals, many from holding pens, 19 % of red wolves survived for at least seven years, Eurasian otters survived for at least two years, over half the giant anteaters (some rehabilitated) survived for at least six months and hare-wallabies survived at least two months. Two of the studies found that red-tailed phascogales survived for less than a year and most Mexican wolves survived less than eight months.

116BEHAVIOUR (1 STUDY)

117Behaviour change (1 study): A controlled study in Argentina found that after being provided with supplementary food and kept in holding pens, released captive-bred giant anteaters were less nocturnal in their activity patterns than released wild-born rehabilitated individuals.

118Assessment: beneficial (effectiveness 72 %; certainty 70 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2527

Release captive-bred individuals to re-establish or boost populations in native range

119Thirty-one studies evaluated the effects of releasing captive-bred mammals to establish or boost populations in their native range. Seven studies were in the USA, three were in Australia and Italy, two studies were in each of Canada, Sweden, Saudi Arabia, the UK, the Netherlands and South Africa and one study was in each of France, Africa, Europe, and North America, Estonia, the USA and Mexico, Poland and China.

120COMMUNITY RESPONSE (0 STUDIES)

121POPULATION RESPONSE (30 STUDIES)

122Abundance (7 studies): Five of five studies (one replicated) and two reviews in Saudi Arabia, Australia, the USA, South Africa, France, the Netherlands and China found that following release of captive-bred (or in one case captive-reared, or including translocated) animals, populations of mountain gazelles, Corsican red deer, Père David’s deer, Eurasian otters and swift foxes increased. The two reviews found that following release of mainly translocated but some captive-bred large carnivores, populations of four of six species increased, and over half of mammal release programmes were considered successful.

123Reproductive success (5 studies): Four studies (one replicated) in Saudi Arabia, the UK and the Netherlands found that released captive-bred (and in some cases some wild-born translocated) mountain gazelles, dormice and some Eurasian otters reproduced successfully and female Arabian oryx reproduced successfully regardless of prior breeding experience. A controlled study in Italy found that released captive-born Apennine chamois reproduced in similar numbers to wild-caught translocated chamois.

124Survival (24 studies): Four of three controlled studies (two replicated) and two reviews in Canada, Canada and the USA, Sweden, Italy and across the world found that released captive-bred swift foxes, European otters and mammals from a review of 49 studies had lower post-release survival rates than did wild-born translocated animals. The other study found that released captive-born Apennine chamois survived in similar numbers to wild-caught translocated chamois. Three studies (one replicated) in the USA and Canada found that released captive-born Key Largo woodrats, Vancouver Island marmots and swift fox pups had lower survival rates than wild-born, wild-living animals. One of the studies also found that Vancouver Island marmots released at two years old were more likely to survive than those released as yearlings. Eleven studies (three replicated) in Italy, Sweden, the UK, Estonia, Poland, Saudi Arabia, Australia and the USA found that following the release of captive-bred (and in some cases some wild-born translocated) animals, Arabian oryx, populations of European otters, European mink and mountain gazelle survived for 2-11 years, roe deer and over a third of brush-tailed rock-wallabies, black-footed ferrets and brown hares survived for 0.5-24 months and dormice populations survived three months to over seven years. A review in Australia found that release programmes for macropod species resulted in successful establishment of populations in 61 % of cases and that 40 % survived over five years, and another review in Australia found that over half of programmes were considered successful. Two studies and a review in the USA, USA and Mexico and South Africa found that over 40 % of released captive-bred American black bears were killed or had to be removed, only one of 10 oribi survived over two years and that most black-footed ferret releases were unsuccessful at maintaining a population.

125BEHAVIOUR (3 STUDIES)

126Use (3 studies): Two studies in the USA and Australia found that following release, most captive-bred and translocated mountain lions that had been held in captivity prior to release and most released captive-bred brush-tailed rock-wallabies established stable home ranges. A controlled study in Italy found that released captive-born Apennine chamois remained closer to the release site than released wild-caught translocated chamois.

127Assessment: beneficial (effectiveness 70 %; certainty 67 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2476

Release captive-bred mammals into fenced areas

128Fourteen studies evaluated the effects of releasing captive-bred mammals into fenced areas. Nine studies were in Australia and one each was in Jordan, South Africa, the USA, Saudi Arabia and Senegal.

129COMMUNITY RESPONSE (0 STUDIES)

130POPULATION RESPONSE (14 STUDIES)

131Abundance (5 studies): Four studies (one replicated) and a review in Australia, Jordan and Senegal found that after releasing captive-bred animals into fenced areas, a population of burrowing bettongs increased, a population of Arabian oryx increased six-fold in 12 years, a population of dorcas gazelle almost doubled over four years, three populations of eastern barred bandicoot initially increased and abundance of eastern barred bandicoots increased. Reproductive success (6 studies): Four studies and a review in South Africa, Australia, Saudi Arabia and Senegal found that following release of captive-bred animals into fenced areas (in some cases with other associated management), African wild dogs, three populations of eastern barred bandicoot, dorcas gazelle and most female black-footed rock-wallabies reproduced, and Arabian gazelles started breeding in the year following the first releases. A study in Australia found that four of five mammal populations released into a predator-free enclosure and one released into a predator-reduced enclosure reproduced, whereas two populations released into an unfenced area with ongoing predator management did not survive to reproduce.

132Survival (10 studies): A study in Australia found that four of five mammal populations released into a predator-free enclosure and one population released into a predator-reduced enclosure survived, whereas two populations released into an unfenced area with ongoing predator management did not. Six studies (one controlled before-and-after study and two replicated studies) in Australia and the USA found that following release of captive-bred animals into fenced areas (in some cases with other associated management), a burrowing bettong population, three eastern barred bandicoot populations and over half of black-footed rock-wallabies survived between one and eight years, most captive-bred hare-wallabies survived at least two months, at least half of black-footed ferrets survived more than two weeks, and bandicoots survived at five of seven sites up to three years after the last release. One study in Australia found that following release into fenced areas, a captive-bred population of red-tailed phascogales survived for less than a year. A study in South Africa found that captive-bred African wild dogs released into fenced reserves in family groups had high survival rates. A randomized, controlled study in Australia found that captive-bred eastern barred bandicoots released into a fenced reserve after time in holding pens had similar post-release survival compared to bandicoots released directly from captivity. Condition (1 study): A randomized, controlled study in Australia found that captive-bred eastern barred bandicoots released into a fenced reserve after time in holding pens had similar post-release body weight compared to those released directly from captivity.

133BEHAVIOUR (0 STUDIES)

134Assessment: beneficial (effectiveness 77 %; certainty 70 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2521

Use holding pens at release site prior to release of captive-bred mammals

135Thirty-one studies evaluated the effects of using holding pens at the release site prior to release of captive-bred mammals. Seven studies were in Australia, and in the USA, four were in the UK, three in Argentina, two in each of Israel, Saudi Arabia and China and one in each of Canada, Namibia, South Africa and Germany.

136COMMUNITY RESPONSE (0 STUDIES)

137POPULATION RESPONSE (30 STUDIES)

138Abundance (2 studies): A study in Saudi Arabia found that a population of captive-bred Arabian sand gazelles kept in holding pens prior to release nearly doubled in size over four years. A before-and-after study in China found that following release of captive-bred animals from a pre-release enclosure into the semi-wild (free-roaming in summer, enclosed in winter and provided with food), Przewalski’s horses increased in number.

139Reproductive success (10 studies): Eight studies (one replicated) and one review in the UK, Saudi Arabia, the USA, Israel and Australia found that following the use of holding pens prior to release (and in some cases provision of supplementary food), captive-bred Eurasian otters, Arabian sand gazelles, eastern-barred bandicoots, some swift foxes, some red wolves and over 33 % of Persian fallow deer reproduced, Arabian gazelles started breeding in the first year and the reproductive success of female Asiatic wild ass increased over 10 years. A study in Australia found that after being kept in a holding pen, all four mammal populations released into an invasive-species-free fenced enclosure reproduced.

140Survival (23 studies): One of three studies (two controlled, one replicated) in the UK, Canada and Australia found that using holding pens prior to release of captive-bred (and some translocated) animals resulted in greater post-release survival for water voles compared to animals released directly into the wild. The other two studies found similar survival rates for eastern barred bandicoots and swift foxes compared to animals released directly into the wild. A replicated study in the USA found that captive-bred Allegheny woodrats kept in holding pens prior to release, had higher early survival rates than those not kept in holding pens, but overall survival rates tended to be lower than wild resident woodrats. Three studies in South Africa, USA and Argentina found that released captive-bred (and some translocated) African wild dogs, riparian brush rabbits and guanacos that spent longer in, and in one case in larger, holding pens had a higher survival rate. Three studies (one controlled) in Australia and the USA found that captive-bred animals kept in holding pens prior to release had similar (bridled nailtail wallabies) or lower (black-footed ferret kits) annual survival rate after release to that of wild-born translocated animals and lower (black-footed ferrets) survival rates than resident animals. Ten studies (including one controlled, before-and-after study) and one review in Saudi Arabia, the USA, Argentina, China, Israel, Australia and Germany found that following the use of holding pens prior to release of captive-bred animals (or in some cases captive-reared/rehabilitated, or with provision of supplementary food), four of four mammal populations, 19 % of red wolves, Asiatic wild ass, Persian fallow deer, most Arabian sand gazelles, most swift foxes, eastern-barred bandicoots and European mink survived at least 1-10 years, over half of giant anteaters, hare-wallabies and Père David’s deer survived for at least 1.5-6 months. Three studies in Namibia, the USA and Australia found that that following the use of holding pens prior to release of captive-bred or reared animals (some provided with nest boxes and/or supplementary food), red-tailed phascogales, most Mexican wolves and African wild dogs survived less than 6-12 months.

141Condition (4 studies): A randomized, controlled study in Australia found that eastern barred bandicoots released after time in holding pens lost a similar proportion of body weight and recovered to a similar weight compared to bandicoots released directly. A controlled study in the UK found that common dormice lost weight after being put into holding pens whereas wild translocated dormice gained weight. A controlled, before-and-after study in Australia found that captive-bred rufous hare-wallabies placed in holding pens prior to release lost body condition in holding pens. A before-and-after study in Australia found that captive-bred brush-tailed rock-wallabies placed in a holding pen prior to release maintained good health.

142BEHAVIOUR (1 STUDY)

143Behaviour change (1 study): A controlled study in Argentina found that after being kept in holding pens and provided with supplementary food, released captive-bred giant anteaters were less nocturnal in their activity patterns than released wild-born rehabilitated individuals.

144Assessment: beneficial (effectiveness 70 %; certainty 65 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2510

Likely to be beneficial

Captive rear in large enclosures prior to release

145Four studies evaluated the effects of captive rearing mammals in large enclosures prior to release. Two studies were in the USA, one was in Mexico and one was in Australia.

146COMMUNITY RESPONSE (0 STUDIES)

147POPULATION RESPONSE (3 STUDIES)

148Reproductive success (1 study): A study in Mexico found that peninsular pronghorn taken from the wild and kept in a large enclosure bred successfully and the population increased, providing stock suitable for reintroductions. Survival (2 studies): A replicated, controlled study in USA found that black-footed ferrets reared in outdoor pens had higher post-release survival rates than did ferrets raised indoors. A controlled study in Australia found that Tasmanian devils reared free-range in large enclosures did not have greater post-release survival rates than animals from intensively managed captive-rearing facilities.

149Condition (1 study): A controlled study in Australia found that Tasmanian devils reared free-range in large enclosures did not gain more body weight post-release compared to animals from intensively managed captive-rearing facilities.

150BEHAVIOUR (1 STUDY)

151Behaviour change (1 study): A controlled study in USA found that captive-bred black-footed ferrets raised in large enclosures dispersed shorter distances post-release than did ferrets raised in small enclosures.

152Assessment: likely to be beneficial (effectiveness 50 %; certainty 46 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2507

Provide live natural prey to captive mammals to foster hunting behaviour before release

153Three studies evaluated the effects of providing live natural prey to captive mammals to foster hunting behaviour before release. One study was in Spain, one was in the USA and one was in Botswana.

154COMMUNITY RESPONSE (0 STUDIES)

155POPULATION RESPONSE (2 STUDIES)

156Survival (2 studies): Two studies in Spain and Botswana found that a rehabilitated Iberian lynx and wild-born but captive-reared orphaned cheetahs and leopards that were provided with live natural prey in captivity survived for between at least three months and 19 months after release.

157BEHAVIOUR (1 STUDY)

158Behaviour change (1 study): A controlled study in the USA found that captive-bred black-footed ferrets fed on live prairie dogs took longer to disperse after release but showed greater subsequent movements than did ferrets not fed with live prairie dogs.

159Assessment: likely to be beneficial (effectiveness 65 %; certainty 40 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2518

Unknown effectiveness

Train captive-bred mammals to avoid predators

160Two studies evaluated the effects of training captive-bred mammals to avoid predators. One study was in Australia and one was in the USA.

161COMMUNITY RESPONSE (0 STUDIES)

162POPULATION RESPONSE (1 STUDY)

163Survival (1 study): A randomized, controlled study in the USA found that training captive-born juvenile black-tailed prairie dogs, by exposing them to predators, increased post-release survival.

164BEHAVIOUR (1 STUDY)

165Behaviour change (1 study): A before-and-after study in Australia found that rufous hare-wallabies could be conditioned to become wary of potential predators.

166Assessment: unknown effectiveness (effectiveness 70 %; certainty 37 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2520

15.13.4 Release captive-bred/translocated mammals

Beneficial

Release translocated/captive-bred mammals in areas with invasive/problematic species eradication/control

167Twenty-two studies evaluated the effects of releasing translocated or captive-bred mammals in areas with eradication or control of invasive or problematic species. Sixteen studies were in Australia, four were in the USA, and one in the UK.

168COMMUNITY RESPONSE (0 STUDIES)

169POPULATION RESPONSE (21 STUDIES)

170Abundance (4 studies): A replicated study in Australia found that increasing amounts of regular predator control increased population numbers of released captive-bred eastern barred bandicoots. Two studies in Australia found that following eradication or control of invasive species, a population of translocated and released captive-bred burrowing bettongs increased and a population of translocated western barred bandicoots increased over four years. A study in Australia found that following the release of captive-bred bridled nailtail wallabies and subsequent predator controls, numbers increased over a three years, but remained low compared to the total number released. Reproductive success (2 studies): A study in Australia found that four of five captive-bred mammal populations released into a predator-free enclosure and one population released into a predator-reduced enclosure produced a second generation, whereas two populations released into an unfenced area with ongoing predator management did not survive to reproduce. A study in Australia found that most female captive-reared black-footed rock-wallabies released into a large predator-free fenced area reproduced.

171Survival (18 studies): Ten studies (one controlled, three replicated, two before-and-after studies) in Australia, and the UK found that following the eradication/control of invasive species (and in some cases release into a fenced area), a translocated population of woylies, western barred bandicoots and red-tailed phascogales survived over four years, released captive-bred eastern barred bandicoots survived up to three years at five of seven sites, offspring of translocated golden bandicoots survived three years, over half of released captive-reared black-footed rock-wallabies survived over two years, captive-bred water voles survived for at least 20 months or over 11 months at over half of release sites, most released captive-bred hare-wallabies survived at least two months, most captive-bred eastern barred bandicoots survived for over three weeks. A replicated study in Australia found that after the control of invasive species, four translocated populations of burrowing bettongs died out within four months. A review of studies in Australia found that in seven studies where red fox control was carried out before or after the release of captive-bred eastern-barred bandicoots, survival varied. A study in Australia found that four of five captive-bred mammal populations released into a predator-free enclosure and one population released into a predator-reduced enclosure survived, whereas two populations released into an unfenced area with ongoing predator management did not. A study in Australia found that captive-bred bridled nailtail wallabies released from holding pens in areas where predators had been controlled had similar annual survival rates to that of wild-born translocated animals. Two studies (one replicated) in the USA found that where predators were managed, at least half of released captive-bred black-footed ferrets survived more than two weeks, but that post-release mortality was higher than resident wild ferrets. A before-and-after study in the USA found following the onset of translocations of black bears away from an elk calving site, survival of the offspring of translocated elk increased.

172Condition (2 studies): A study Australia found that wild-born golden bandicoots, descended from a translocated population released into a predator-free enclosure, maintained genetic diversity relative to the founder and source populations. A replicated, before-and-after study in Australia found that one to two years after release into predator-free fenced reserves, translocated eastern bettongs weighed more and had improved nutritional status compared to before release.

173BEHAVIOUR (1 STUDY)

174Behaviour change (1 study): A replicated, before-and-after study in the USA found that translocated Utah prairie dogs released after the control of native predators into an area with artificial burrows showed low site fidelity and different pre- and post-release behaviour.

175Assessment: beneficial (effectiveness 69 %; certainty 62 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2469

Release translocated/captive-bred mammals in family/ social groups

176Twenty-six studies evaluated the effects of releasing translocated or captive-bred mammals in family or social groups. Eleven were in the USA, seven were in South Africa and one was in each of Poland, Zimbabwe, along the USA–Canada border, Russia, Italy, Canada, China and India.

177COMMUNITY RESPONSE (0 STUDIES)

178POPULATION RESPONSE (22 STUDIES)

179Abundance (4 studies): A study in the USA found that a translocated population of Rocky Mountain bighorn sheep released in groups increased at a similar rate to that of a population newly established through natural recolonization. A replicated, controlled study in the USA found that after translocating black-tailed prairie dogs in social groups to areas with artificial burrows, colonies increased in size over four years. A replicated study in Canada found that following translocation of elk, most of which had been kept in holding pens in groups, numbers increased at two of four sites. A study in the USA found that following the release of captive-reared bighorn sheep in groups, the overall population declined over 14 years.

180Reproductive success (11 studies): A study in the USA found that captive-reared bighorn sheep released in groups had similar population recruitment rates compared to wild-reared sheep. A replicated, paired study in the USA found that black-tailed prairie dogs translocated as family groups had higher reproductive success than those translocated in non-family groups. A replicated study in the USA found that translocated gray wolves had similar breeding success when adult family groups were released together from holding pens or when young adults were released directly into the wild. Six of eight studies (one replicated) in Poland, Russia, South Africa, the USA and the USA–Canada border found that when translocated and/ or captive-bred animals were released in social or family groups, cheetahs, European bison, lions, African wild dogs, most European beavers and some swift foxes reproduced successfully. One study found that one of two translocated Cape buffalo groups released after being held in a holding pen formed a single herd and reproduced, while the other scattered and escaped the reserve. One study found that no Gunnison’s prairie dogs reproduced during the first year.

181Survival (19 studies): One of three studies (one controlled, before-and-after) in the USA found that when translocated or captive-bred animals were released in family or social groups, captive-reared bighorn sheep had similar survival compared to wild-reared sheep, whereas two found lower survival compared to wild white-tailed deer and San Joaquin kit foxes. Three replicated studies (one controlled, one paired) in the USA found that when translocated as a social or family group, black-tailed prairie dogs had higher and white-tailed deer and gray wolves had similar survival rates to those translocated as unrelated groups or individuals. Ten studies (one replicated) in Poland, Russia, Italy, South Africa, the USA, USA–Canada border, China and India found that when translocated and/or captive-bred animals were released in social or family groups, a population of Przewalski’s horses and European bison persisted 5-11 years, lions, most swift foxes and European beavers and half or more cheetahs survived for at least one year, and one-horned rhinoceroses and over half of Gunnison’s prairie dogs and Eurasian badgers survived at least 1-6 months. Three studies in the USA and South Africa found that when translocated or captive-bred animals were released in family or social groups (some provided with artificial refuges and/or supplementary food), most Mexican wolves did not survive over eight months and all rock hyraxes died within 90 days. A study in South Africa found that translocated and captive-bred African wild dogs released in family groups into fenced reserves had high survival rates.

182Condition (1 study): A study in China found that following the release of captive-bred Przewalski’s horses in groups, the population had a lower genetic diversity than two captive populations.

183BEHAVIOUR (4 STUDIES)

184Behaviour change (4 studies): Two replicated, controlled (one before-and-after) studies in the USA found that when translocated as a social or family group, white-tailed deer had similar average dispersal distances and Utah prairie dogs had similar release site fidelity and post-release behaviour compared to those translocated as unrelated groups. One found that deer translocated together did not stay together, whether they had previously been part of the same social group or not. A study in Zimbabwe found that a translocated lion family joined with immigrant lions and formed a new pride. A study in South Africa found that translocated lions that were released in groups that had already been socialised and formed into prides, established stable home ranges.

185Assessment: beneficial (effectiveness 70 %; certainty 65 %; harms 5 %).

https://www.conservationevidence.com/​actions/​2463

Release translocated/captive-bred mammals into area with artificial refuges/breeding sites

186Seventeen studies evaluated the effects of releasing translocated or captive-bred mammals into areas with artificial refuges or breeding sites. Five studies were in the USA, three were in Australia, three were in Spain, two were in the UK and one was in each of Ireland, South Africa, Hungary and Slovakia, the Czech Republic and Poland.

187COMMUNITY RESPONSE (0 STUDIES)

188POPULATION RESPONSE (15 STUDIES)

189Abundance (5 studies): Two of three studies (two replicated, two controlled) in Spain and the USA found that translocation release sites with artificial burrows provided had higher abundances of European rabbits and densities of California ground squirrels compared to those without. The other study found that abundance of European rabbits following translocation was similar with and without artificial burrows provided. A replicated, controlled study in the USA found that after translocating black-tailed prairie dogs to areas with artificial burrows, colonies increased in size. A before-and-after study in Spain found that translocating European rabbits into areas with artificial refuges to supplement existing populations did not alter rabbit abundance, although two of three populations persisted for at least three years.

190Reproductive success (4 studies): Three studies in Australia, Ireland and the UK found that released captive-bred sugar gliders, most translocated female red squirrels and some translocated pine martens provided with nest boxes and supplementary food reproduced. A study of 12 translocation projects in Slovakia, the Czech Republic and Poland found that translocated European ground squirrels released initially into enclosures or burrows with retention caps reproduced after release, whereas those without enclosures or burrows dispersed from release sites.

191Survival (9 studies): Five of eight studies in Australia, the USA, UK, Ireland and South Africa found that at release sites with artificial refuges, and in some cases food provided, a population of captive-bred sugar gliders survived at least three years, two of three populations of red-tailed phascogales survived for more than four years, most translocated black bears survived at least one year and over half translocated red squirrels and pine martens survived 8-12 months. Three studies found that at release sites with artificial refuges, food and in one case water provided, no translocated red squirrels survived more than five months, all translocated rock hyraxes died within three months and most translocated Tipton and Heermann’s kangaroo rat spp. died within five days. A randomised, replicated, controlled study in Hungary found that translocated European ground squirrels released into plugged artificial burrows had higher recapture rates than those released into unplugged artificial burrows.

192BEHAVIOUR (3 STUDIES)

193Use (2 studies): Two studies in Australia found that released captive-bred sugar gliders used artificial nest boxes provided.

194Behaviour change (1 study): A replicated, before-and-after study in the USA found that translocated Utah prairie dogs released into an area with artificial burrows, after the control of native predators, tended to leave the release site and spent more time being vigilant than before.

195Assessment: beneficial (effectiveness 62 %; certainty 62 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2453

Likely to be beneficial

Release translocated/captive-bred mammals at a specific time (e.g. season, day/night)

196Seven studies evaluated the effects of releasing translocated or captive-bred mammals at a specific time (season or day/night). Three studies were in the USA and one each was in the UK, Canada, Ireland and Hungary.

197COMMUNITY RESPONSE (0 STUDIES)

198POPULATION RESPONSE (7 STUDIES)

199Survival (7 studies): Four of five studies in the UK, Canada and the USA found that translocated common dormice, black bears and Canadian lynx and captive-bred swift foxes released in a specific season had higher survival rates than those released during another season. The other study found that red squirrels translocated in autumn and winter had similar survival rates. A randomised, replicated, controlled study in Hungary found that translocated European ground squirrels released during the morning had higher recapture rates than those released during the afternoon. A study in the USA found that most translocated kangaroo rats released at dusk in artificial burrows supplied with food died within five days of release.

200Condition (1 study): A study in the UK found that common dormice translocated during summer lost less weight than those translocated during spring.

201BEHAVIOUR (2 STUDIES)

202Behaviour change (2 studies): Two studies in the UK and USA found that common dormice translocated during spring and black bears translocated during winter travelled shorter distances or settled closer to the release site than those translocated during summer.

203Assessment: likely to be beneficial (effectiveness 70 %; certainty 60 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2447

Release translocated/captive-bred mammals in larger unrelated groups

204Five studies evaluated the effects of releasing translocated or captive-bred mammals in larger unrelated groups. Two studies were in South Africa, one was in Namibia and South Africa, one was in the USA and one was in Australia.

205COMMUNITY RESPONSE (0 STUDIES)

206POPULATION RESPONSE (5 STUDIES)

207Reproductive success (3 studies): A replicated, paired sites study in the USA found that black-tailed prairie dogs translocated in larger groups had higher reproductive success than smaller groups. A study in South Africa found that Cape buffalo translocated to a fenced reserve as a larger group formed a single herd and reproduced, whilst a smaller group separated. A study in South Africa found that rehabilitated and captive-bred cheetahs released in groups (unrelated and family) and as individuals reproduced.

208Survival (4 studies): A replicated, paired sites study in the USA found that black-tailed prairie dogs translocated in larger groups had higher initial daily survival rate than smaller groups. Two studies (one controlled) in Namibia and South Africa and Australia found that releasing translocated black rhinoceroses and burrowing bettongs in larger groups did not increase survival. A study in South Africa found that most adult rehabilitated and captive-bred cheetahs released in groups (unrelated and family) and as individuals survived at least one year.

209BEHAVIOUR (2 STUDIES)

210Behaviour change (2 studies): A replicated, paired sites study in the USA found that black-tailed prairie dogs translocated in larger groups attracted more immigrants than smaller groups. A study in South Africa found that Cape buffalo translocated as a larger group formed a single herd and stayed in the fenced reserve, whilst a smaller group scattered and escaped the reserve. Assessment: likely to be beneficial (effectiveness 67 %; certainty 54 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2462

Release translocated/captive-bred mammals to areas outside historical range

211Seven studies evaluated the effects of releasing translocated or captive-bred mammals to areas outside their historical range. Three studies were in Australia, one study was in each of Kenya, France and South Africa, and one was a review of studies in Andorra, Spain and France.

212Terrestrial Mammal Conservation

213COMMUNITY RESPONSE (0 STUDIES)

214POPULATION RESPONSE (7 STUDIES)

215Abundance (5 studies): Three of four studies in Kenya, Australia, France, and South Africa found that after translocating mammals to areas outside their historical range, populations increased for Alpine marmots, most of 22 herbivorous species and bridled nailtail wallabies (including captive and enclosure bred animals). A study in Kenya found that a population of translocated roan persisted for more than six years but did not increase. A review of studies in Andorra, Spain and France found that following translocation to areas outside their native range, alpine marmots had similar densities and family group sizes to those of populations in their native range. Reproductive success (1 study): A study in Kenya found that a population of roan translocated into an area outside their native range persisted and bred for more than six years.

216Survival (3 studies): A study in Australia found that captive-bred, translocated and enclosure born bridled nailtail wallabies released into areas outside their historical range had annual survival rates of 40–88 % over four years. A study in Australia found that most captive-bred Tasmanian devils released into an area outside their native range survived over four months. A study in Australia found that half the captive-bred and wild-caught translocated eastern barred bandicoots released to a red fox-free island outside their historical range survived for at least two months.

217BEHAVIOUR (0 STUDIES)

218Assessment: likely to be beneficial (effectiveness 70 %; certainty 52 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2443

Release translocated/captive-bred mammals to islands without invasive predators

219Six studies evaluated the effects of releasing translocated or captive-bred mammals to islands without invasive predators. The six studies were in Australia.

220COMMUNITY RESPONSE (0 STUDIES)

221POPULATION RESPONSE (7 STUDIES)

222Abundance (2 studies): A study in Australia found that following release of captive-bred dibblers on to an island free of introduced predators, numbers increased. A replicated study in Australia found that following release of captive-bred and wild-born brush-tailed bettong onto islands free of foxes or cats, numbers increased on two of four islands.

223Reproductive success (3 studies): A study in Australia found that captive-bred proserpine rock-wallabies released on an island without introduced predators established a breeding population. Two studies in Australia found that following release on to islands without invasive predators, captive-bred rufous hare-wallabies and captive-bred dibblers.

224Survival (3 studies): A review of 28 translocation studies in Australia found that 67 % of marsupial populations translocated to islands without predators survived more than five years, compared to 0 % translocated to islands with predators and 20 % translocated to the mainland. A study in Australia found that most captive-bred rufous hare-wallabies released on an island without non-native predators survived more than a year. A replicated study in Australia found that wild-born golden bandicoots descended from translocated populations released onto two predator-free islands persisted for 2–3 years. Condition (1 study): A replicated study in Australia found that wild-born golden bandicoots descended from translocated populations that had been released onto two predator-free islands, maintained genetic diversity relative to founder and source populations.

225BEHAVIOUR (0 STUDIES)

226Assessment: likely to be beneficial (effectiveness 80 %; certainty 60 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2464

15.13.5 Other

Likely to be beneficial

Place orphaned or abandoned wild young with captive foster parents

227Two studies evaluated the effects of placing orphaned or abandoned wild young with captive foster parents. One study was in Canada and one was in the USA.

228COMMUNITY RESPONSE (0 STUDIES)

229POPULATION RESPONSE (1 STUDY)

230Survival (1 study): A controlled study in the USA found that stranded sea otter pups reared in captivity by foster mothers had higher post-release survival than did unfostered pups reared mostly alone, and similar survival to wild pups.

231BEHAVIOUR (2 STUDIES)

232Behaviour change (2 studies): A study in Canada found that a captive white-tailed deer adopted a wild orphaned fawn. A controlled study in the USA found that stranded sea otter pups reared in captivity by foster mothers began foraging earlier than did unfostered pups reared mostly alone.

233Assessment: likely to be beneficial (effectiveness 70 %; certainty 40 %; harms 7 %).

https://www.conservationevidence.com/​actions/​2364

Place orphaned or abandoned wild young with wild foster parents

234Three studies evaluated the effects of placing orphaned or abandoned wild young with wild foster parents. One study was in the USA, one was in South Africa and one was in Botswana.

235COMMUNITY RESPONSE (0 STUDIES)

236POPULATION RESPONSE (3 STUDIES)

237Survival (3 studies): Two studies (one controlled) in the USA and Botswana, found that orphaned young black bears and African wild dogs had greater or equal survival compared to animals released alone or young of wild mammals with their biological parents. A study in South Africa found that an orphaned cheetah cub was not accepted by a family of cheetahs.

238BEHAVIOUR (0 STUDIES)

239Assessment: likely to be beneficial (effectiveness 52 %; certainty 42 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2343

Provide supplementary water to increase reproduction/ survival

240Six studies evaluated the effects on mammals of providing supplementary water to increase reproduction/survival. Two studies were in Australia and one each was in Oman, Portugal, Saudi Arabia and the USA and Mexico. COMMUNITY RESPONSE (0 STUDIES)

241POPULATION RESPONSE (5 STUDIES)

242Abundance (2 studies): A replicated study in the USA and Mexico found that providing supplementary water was associated with increases in desert bighorn sheep population size. A study in Oman found that a released captive-bred Arabian oryx population initially provided with supplementary water and food increased over 14 years.

243Reproduction (2 studies): A study in Saudi Arabia found that released captive-bred Arabian gazelles initially provided with supplementary water and food after release into a fenced area started breeding in the first year. A study in Australia found that most female released captive-reared black-footed rock-wallabies provided with supplementary water after release into a large predator-free fenced area reproduced in the first two years.

244Survival (2 studies): A controlled, before-and-after study in Australia found that most released captive-bred hare-wallabies provided with supplementary water, along with supplementary food and predator control, survived at least two months after release into a fenced peninsula. A study in Australia found that over half of released captive-reared black-footed rock-wallabies provided with supplementary water after release into a large predator-free fenced area survived for at least two years.

245BEHAVIOUR (1 STUDY)

246Use (1 study): A replicated study in Portugal found that artificial waterholes were used by European rabbits and stone martens.

247Assessment: likely to be beneficial (effectiveness 80 %; certainty 60 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2396

Rehabilitate injured, sick or weak mammals

248Thirteen studies evaluated the effects of rehabilitating injured, sick or weak mammals. Four studies were in the UK, three were in Spain, two were in Argentina and one each was in Uganda, Australia, the USA and Brazil.

249COMMUNITY RESPONSE (0 STUDIES)

250POPULATION RESPONSE (12 STUDIES)

251Survival (11 studies): Five studies, in the UK and Spain, found that varying proportions of European hedgehogs released after being rehabilitated in captivity survived during post-release monitoring periods, which ranged from two weeks to 136 days. Five studies, in Australia, Spain, the USA and Brazil, found that four koalas, an Iberian lynx, a gray wolf, a puma and two brown bears released following rehabilitation in captivity survived for varying durations during monitoring periods, which ranged in length from three months to up to seven years. A study in Argentina found that over half of released rehabilitated and captive-reared giant anteaters survived for at least six months.

252Condition (2 studies): A study in Uganda found that a snare wound in a white rhinoceros healed after treatment and rehabilitation. A study in the UK found that two of three rehabilitated European hedgehogs lost 12-36 % of their body weight after release into the wild.

253BEHAVIOUR (1 STUDY)

254Behaviour change (1 study): A controlled study in Argentina found that released wild-born rehabilitated giant anteaters were more nocturnal in their activity patterns than captive-bred individuals.

255Assessment: likely to be beneficial (effectiveness 70 %; certainty 55 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2352

Trade-off between benefit and harms

Hand-rear orphaned or abandoned young in captivity

256Six studies evaluated the effects of hand-rearing orphaned mammals. Two were in the USA, one each was in Australia, South Africa and India and one was in six countries across North America, Europe and Asia.

257COMMUNITY RESPONSE (0 STUDIES)

258POPULATION RESPONSE (5 STUDIES)

259Reproductive success (1 study): One study in India found that three hand-reared orphaned or abandoned greater one-horned rhinoceroses gave birth in the wild. Survival (5 studies): Five studies (including one controlled and one replicated) in Australia, the USA, India and in six countries across North America, Europe and Asia, found that some hand-reared orphaned or abandoned ringtail possums, white-tailed deer, sea otters, bears and greater one-horned rhinoceroses survived for periods of time after release.

260BEHAVIOUR (1 STUDY)

261Behaviour change (1 study): A study in South Africa found that a hand-reared, orphaned serval established a home range upon release.

262Assessment: trade-off between benefit and harms (effectiveness 50 %; certainty 40 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2358

Provide supplementary food to increase reproduction/ survival

263Twenty-four studies evaluated the effects on mammals of providing supplementary food to increase reproduction/survival. Nine studies were in the USA, two were in Canada, two were in South Africa, two were in Poland, and one each was in Sweden, the Netherlands, eSwatini, Spain, Portugal, Slovenia, Austria, Norway and Sweden and one was across North America and Europe.

264COMMUNITY RESPONSE (0 STUDIES)

265POPULATION RESPONSE (18 STUDIES)

266Abundance (8 studies): Four of eight studies (incuding four controlled, two site comparisons and five before-and-after studies) in the USA, Canada, South Africa, Poland and Austria found that supplementary feeding increased the abundance or density of bank voles, red squirrels, striped mice, brown hyena and black-backed jackals. One study found a temporary increased in prairie vole abundance. The other three studies found supplementary feeding not to increase abundance or density of white-footed mice, northern flying squirrels, Douglas squirrels or Eurasian otters.

267Reproduction (8 studies): Four of five controlled studies (three also replicated) in the USA, South Africa, Norway and Sweden, Sweden and Spain, found that supplementary food increased the proportion of striped mice that were breeding, the number of arctic fox litters and the size of prairie vole litters. However, there was no increase in the number of arctic fox cubs in each litter or the proportion of female Iberian lynx breeding. One of two replicated studies (one site comparison and one controlled), in the Netherlands and the USA, found that supplementary feeding increased the number of young wild boar produced and recruited in to the population. The other study found that the number of mule deer produced/adult female did not increase. A review of studies across North America and Europe found that supplementary feeding increased ungulate reproductive rates in five of eight relevant studies.

268Survival (9 studies): Four of eight studies (including seven controlled studies and two before-and-after studies) in the USA, Canada, Poland and Spain, found that supplementary feeding increased survival of mule deer, bank voles, northern flying squirrels and eastern cottontail rabbits. Five studies found no increase in survival for white-tailed deer, Douglas squirrels, mule deer, Rocky Mountain bighorn sheep lambs or Iberian lynx. A review of studies across North America and Europe found that supplementary feeding increased ungulate survival in four out of seven relevant studies.

269Condition (4 studies): One of three studies (including two controlled and two before-and-after studies) in Poland, the USA, and Canada, found that supplementary food lead to weight gain or weight recovery in bank voles. One study found no body mass increase with supplementary feeding in northern flying squirrels and Douglas squirrels. The third study found mixed results, with supplementary feeding increasing weight gains in some cotton rats, depending on their sex, weight and the time of year. A review of studies from across North America and Europe found that different proportions of studies found supplementary feeding to improve a range of measures of ungulate condition.

270BEHAVIOUR (6 STUDIES)

271Use (2 studies): A replicated, controlled study in Sweden found that supplementary food increased occupancy of Arctic fox dens. A replicated study in Portugal found that artificial feeding stations were used by European rabbits.

272Behaviour (4 studies): Two of three replicated studies (two also controlled), in eSwatini, Slovenia and the USA, found that supplementary feeding led to reduced home range sizes or shorter movements of red deer and elk. The third study found home ranges and movement distances to be similar between fed and unfed multimammate mice. One replicated study in Poland found that supplementary feeding of ungulates altered brown bear behaviour.

273Assessment: trade-off between benefit and harms (effectiveness 70 %; certainty 70 %; harms 20 %).

https://www.conservationevidence.com/​actions/​2367

Unknown effectiveness

Cease/reduce payments to cull mammals

274One study evaluated the effects of ceasing or reducing payments to cull mammals. This study was in Sweden and Norway.

275COMMUNITY RESPONSE (0 STUDIES)

276POPULATION RESPONSE (1 STUDY)

277Survival (1 study): A before-and-after study in Sweden and Norway found that fewer brown bears were reported killed after the removal of financial hunting incentives.

278BEHAVIOUR (0 STUDIES)

279Assessment: unknown effectiveness (effectiveness 61 %; certainty 39 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2349

Graze herbivores on pasture, instead of sustaining with artificial foods

280One study evaluated the effects of grazing mammalian herbivores on pasture, instead of sustaining with artificial foods. This study was in South Africa. COMMUNITY RESPONSE (0 STUDIES)

281POPULATION RESPONSE (1 STUDY)

282Reproductive success (1 study): A site comparison study in South Africa found that a population of roan antelope grazed on pasture had a higher population growth rate than populations provided solely with imported feed. BEHAVIOUR (0 STUDIES)

283Assessment: unknown effectiveness (effectiveness 65 %; certainty 35 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2398

No evidence found (no assessment)

284We have captured no evidence for the following interventions:

285• Temporarily hold females and offspring in fenced area to increase survival of young.

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