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What Works in Conservation 2021

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

15. Terrestrial mammal conservation

15.8 Threat: Invasive alien and other problematic species

Texte intégral

15.8.1 Invasive non-native/alien species/diseases

Beneficial

Remove/control non-native mammals

1Twenty-five studies evaluated the effects on non-controlled mammals of removing or controlling non-native mammals. Twenty-one studies were in Australia, and one was in each of France, the UK, Equador and the USA.

2COMMUNITY RESPONSE (0 STUDIES)

3POPULATION RESPONSE (24 STUDIES)

4Abundance (21 studies): Ten of 18 controlled, before-and-after or site comparison studies, in Australia, found that after controlling red foxes, abundances, densities or trapping frequencies increased for rock-wallaby spp., eastern grey kangaroo, woylie, , brush-tail possum, tammar wallaby, chuditch and quenda. Seven studies found mixed results with increases in some species but not others, increases followed by declines or increases only where cats as well as foxes were controlled. The other study found no increase in bush rat numbers with fox control. One of three replicated, before-and-after studies (including two controlled studies), in Australia, France and Ecuador, found that control of invasive rodents increased numbers of lesser white-toothed shrews and greater white-toothed shrews. One study found that Santiago rice rat abundance declined less with rodent control and one found mixed results, with increased numbers of short-tailed mice at one out of four study sites.

5Survival (1 study): A replicated, controlled study in Australia found that controlling red foxes increased survival of juvenile eastern grey kangaroos. Occupancy/range (3 studies): Three studies (two before-and-after, one controlled), in the UK and Australia, found that after controlling non-native American mink, red foxes and European rabbits, there were increases in ranges or proportions of sites occupied by water vole, common brushtail possum, long-nosed potoroo and southern brown bandicoot and four native small mammal species.

6BEHAVIOUR (1 STUDY)

7Behaviour change (1 study): A before-and-after study in the USA found that following removal of feral cats, vertebrate prey increased as a proportion of the diet of island foxes.

8Assessment: beneficial (effectiveness 67 %; certainty 70 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2504

Likely to be beneficial

Remove/control non-native mammals within a fenced area

9One study evaluated the effects on native mammals of removing or controlling non-native mammals within a fenced area. This study was in Australia.

10COMMUNITY RESPONSE (1 STUDY)

11Richness/diversity (1 study): A site comparison study in Australia found that in a fenced area where invasive cats, red foxes and European rabbits were removed, native mammal species richness was higher than outside the fenced area.

12POPULATION RESPONSE (1 STUDY)

13Abundance (1 study): A site comparison study in Australia found that in a fenced area where invasive cats, red foxes and European rabbits were removed, native mammals overall and two out of four small mammal species were more abundant than outside the fenced area.

14BEHAVIOUR (0 STUDIES)

15Assessment: likely to be beneficial (effectiveness 65 %; certainty 40 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2528

Use conditioned taste aversion to prevent non-target species from entering traps

16One study evaluated the effects on mammals of using conditioned taste aversion to prevent non-target species from entering traps. This study was in the USA.

17COMMUNITY RESPONSE (0 STUDIES)

18POPULATION RESPONSE (0 STUDIES)

19BEHAVIOUR (1 STUDY)

20Behaviour change (1 study): A replicated, controlled study in the USA found that using bait laced with lithium chloride reduced the rate of entry of San Clemente Island foxes into traps set for feral cats.

21Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2536

Use drugs to treat parasites

22Seven studies evaluated the effects on mammals of using drugs to treat parasites. Three studies were in the USA, two were in Spain, one was in Germany and one was in Croatia.

23COMMUNITY RESPONSE (0 STUDIES)

24POPULATION RESPONSE (7 STUDIES)

25Survival (1 study): A randomized, replicated, controlled study the USA found that medical treatment of Rocky Mountain bighorn sheep against lungworm did not increase lamb survival.

26Condition (6 studies): Three of four before-and-after studies (one controlled), in Germany, the USA and Croatia, found that after administering drugs to mammals, parasite burdens were reduced in roe deer and in wild boar piglets and numbers of white-tailed deer infected were reduced. A third study found that levels of lungworm larvae in bighorn sheep faeces were reduced one month after drug treatment but not after three to seven months. One of these studies also found that the drug treatment resulted in increased body weight in roe deer fawns. A replicated, controlled, before-and-after study in Spain found that higher doses of ivermectin treated sarcoptic mange in Spanish ibex faster than lower doses, and treatment was more effective in animals with less severe infections. A replicated, before-and-after study in Spain found that after injecting Spanish ibex with ivermectin to treat sarcoptic mange a mange-free herd was established.

27BEHAVIOUR (0 STUDIES)

28Assessment: likely to be beneficial (effectiveness 55 %; certainty 60 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2587

Use reward removal to prevent non-target species from entering traps

29One study evaluated the effects on mammals of using reward removal to prevent non-target species from entering traps. This study was in the USA. COMMUNITY RESPONSE (0 STUDIES)

30POPULATION RESPONSE (0 STUDIES)

31BEHAVIOUR (1 STUDY)

32Behaviour change (1 study): A replicated, controlled study in the USA found that when reward removal was practiced, the rate of San Clemente Island fox entry into traps set for feral cats was reduced.

33Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2537

Unknown effectiveness

Modify traps used in the control/eradication of non-native species to avoid injury of non-target mammal

34One study evaluated the effects of modifying traps used in the control or eradication of non-native species to avoid injury of non-target mammals. This study was in the USA.

35COMMUNITY RESPONSE (0 STUDIES)

36POPULATION RESPONSE (1 STUDY)

37Condition (1 study): A before-and-after study in the USA found that modifying traps used for catching non-native mammals reduced moderate but not severe injuries among incidentally captured San Nicolas Island foxes.

38BEHAVIOUR (0 STUDIES)

39Assessment: unknown effectiveness (effectiveness 40 %; certainty 22 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2535

Remove/control non-native invertebrates

40One study evaluated the effects on mammals of removing or controlling non-native invertebrates. This study was in the USA.

41COMMUNITY RESPONSE (0 STUDIES)

42POPULATION RESPONSE (1 STUDY)

43Abundance (1 study): A replicated, controlled, before-and-after study the USA found that after the control of red imported fire ants, capture rates of northern pygmy mice increased.

44BEHAVIOUR (0 STUDIES)

45Assessment: unknown effectiveness (effectiveness 67 %; certainty 25 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2501

Remove/control non-native plants

46Two studies evaluated the effects on mammals of removing or controlling non-native invasive plants. Both studies were in the USA.

47COMMUNITY RESPONSE (1 STUDY)

48Richness/diversity (1 study): A replicated study in the USA found that control of introduced saltcedar did not change small mammal species richness.

49POPULATION RESPONSE (1 STUDY)

50Abundance (1 study): A site comparison study in the USA found that partial removal of velvet mesquite did not increase abundances of six mammal species.

51BEHAVIOUR (0 STUDIES)

52Assessment: unknown effectiveness (effectiveness 8 %; certainty 25 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2529

No evidence found (no assessment)

53We have captured no evidence for the following interventions:

  • Control non-native prey species to reduce populations and impacts of non-native predators

  • Control non-native/problematic plants to restore habitat

  • Provide artificial refuges for prey to evade/escape non-native predators

  • Reintroduce top predators to suppress and reduce the impacts of smaller non-native predator and prey species

  • Remove/control non-native amphibians (e.g. cane toads)

  • Remove/control non-native species that could interbreed with native species.

15.8.2 Problematic native species/diseases

Beneficial

Use vaccination programme

54Seven studies evaluated the effects on mammals of using vaccination programmes. Three studies were in the UK and one study was in each of Belgium, Spain, Poland and Ethiopia.

55COMMUNITY RESPONSE (0 STUDIES)

56POPULATION RESPONSE (7 STUDIES)

57Abundance (1 study): A before-and-after study in Poland found that following an anti-rabies vaccination programme, red fox numbers increased.

58Condition (6 studies): Five studies (including three replicated, three controlled and two before-and-after studies) in Belgium, Spain and the UK found that following vaccination, rabies was less frequent in red foxes, numbers of Eurasian badgers infected with tuberculosis was reduced and European rabbits developed immunity to myxomatosis and rabbit haemorrhagic disease. One of the studies also found that vaccination reduced the speed and extent of infection in infected Eurasian badgers. A study in Ethiopia found that following vaccination of Ethiopian wolves, a rabies outbreak halted.

59BEHAVIOUR (0 STUDIES)

60Assessment: beneficial (effectiveness 80 %; certainty 70 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2582

Likely to be beneficial

Cull disease-infected animals

61One study evaluated the effects on mammals of culling disease-infected animals. This study was in Tasmania.

62COMMUNITY RESPONSE (0 STUDIES)

63POPULATION RESPONSE (1 STUDY)

64Condition (1 study): A before-and-after, site comparison study in Tasmania found that culling disease-infected Tasmanian devils resulted in fewer animals with large tumours associated with late stages of the disease.

65BEHAVIOUR (0 STUDIES)

66Assessment: likely to be beneficial (effectiveness 60 %; certainty 40 %; harms 15 %).

https://www.conservationevidence.com/​actions/​2586

Trade-off between benefit and harms

Remove or control predators

67Ten studies evaluated the effects on non-controlled mammals of removing or controlling predators. Seven studies were in North America, one was in Finland, one in Portugal and one in Mexico.

68COMMUNITY RESPONSE (0 STUDIES)

69POPULATION RESPONSE (10 STUDIES)

70Abundance (6 studies): Three of six studies (including three controlled, one before-and-after and one replicated, paired sites study), in Finland Portugal, Mexico and the USA, found that removing predators increased abundances of pronghorns, moose and European rabbits and Iberian hares. One of these studies also found that mule deer abundance did not increase. The other three studies found that removing predators did not increase mountain hare, caribou or desert bighorn sheep abundance.

71Reproductive success (2 studies): Two replicated, before-and-after studies (one also controlled), in the USA, found that predator removal was associated with increased breeding productivity of white-tailed deer and less of a productivity decline in pronghorns. However, one of these studies also found that there was no change in breeding productivity of mule deer.

72Survival (5 studies): Two of five before-and-after studies (including two controlled studies and one replicated study), in the USA, Canada and the USA and Canada combined, found that controlling predators did not increase survival of caribou calves, or of calf or adult female caribou. Two studies found that moose calf survival and woodland caribou calf survival increased with predator control. The other study found mixed results with increases in white-tailed deer calf survival in some but not all years with predator control. BEHAVIOUR (0 STUDIES)

73Assessment: trade-off between benefit and harms (effectiveness 50 %; certainty 50 %; harms 46 %).

https://www.conservationevidence.com/​actions/​2613

Unknown effectiveness

Control ticks/fleas/lice in wild mammal populations

74Two studies evaluated the effects of controlling ticks, fleas or lice in wild mammal populations. Both studies were in the USA.

75COMMUNITY RESPONSE (0 STUDIES)

76POPULATION RESPONSE (2 STUDIES)

77Condition (2 studies): A replicated, paired sites, controlled study in the USA found that a grain-bait insecticide product did not consistently reduce flea burdens on Utah prairie dogs. A controlled study the USA found that treating wolves with ivermectin cleared them of infestations of biting dog lice.

78BEHAVIOUR (0 STUDIES)

79Assessment: unknown effectiveness (effectiveness 50 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2589

Establish populations isolated from disease

80One study evaluated the effects on mammals of establishing populations isolated from disease. The study was in sub-Saharan Africa.

81COMMUNITY RESPONSE (0 STUDIES)

82POPULATION RESPONSE (1 STUDY)

83Condition (1 study): A site comparison study throughout sub-Saharan Africa found that fencing reduced prevalence of canine distemper but not of rabies, coronavirus or canine parvovirus in African wild dogs.

84BEHAVIOUR (0 STUDIES)

85Assessment: unknown effectiveness (effectiveness 25 %; certainty 20 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2588

Provide diversionary feeding for predators

86One study evaluated the effects on potential prey mammals of providing diversionary feeding for predators. This study was in Canada.

87COMMUNITY RESPONSE (0 STUDIES)

88POPULATION RESPONSE (1 STUDY)

89Survival (1 study): A controlled, before-and-after study in Canada found that diversionary feeding of predators appeared to increase woodland caribou calf survival.

90BEHAVIOUR (0 STUDIES)

91Assessment: unknown effectiveness (effectiveness 67 %; certainty 20 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2578

Remove or control competitors

92Two studies evaluated the effects on non-controlled mammals of removing or controlling competitors. One study was across Norway and Sweden and one was in Norway.

93COMMUNITY RESPONSE (0 STUDIES)

94POPULATION RESPONSE (1 STUDY)

95Reproductive success (1 study): A replicated, controlled study in Norway and Sweden found that red fox control, along with supplementary feeding, was associated with an increase in arctic fox litters.

96BEHAVIOUR (1 STUDY)

97Use (1 study): A controlled study in Norway found that where red foxes had been controlled arctic foxes were more likely to colonize.

98Assessment: unknown effectiveness (effectiveness 70 %; certainty 33 %; harms 12 %).

https://www.conservationevidence.com/​actions/​2575

Sterilize predators

99One study evaluated the effects on potential prey mammals of sterilizing predators. This study was in the USA and Canada.

100COMMUNITY RESPONSE (0 STUDIES)

101POPULATION RESPONSE (1 STUDY)

102Survival (1 study): A before-and-after study in the USA and Canada found that sterilising some wolves (combined with trapping and removing others) did not increase caribou survival.

103BEHAVIOUR (0 STUDIES)

104Assessment: unknown effectiveness (effectiveness 0 %; certainty 15 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2573

Train mammals to avoid problematic species

105Two studies evaluated the effects of training mammals to avoid problematic species. Both studies were in Australia.

106COMMUNITY RESPONSE (0 STUDIES)

107POPULATION RESPONSE (1 STUDY)

108Survival (1 study): A controlled study in Australia found that training greater bilbies to avoid introduced predators did not increase their post-release survival.

109BEHAVIOUR (2 STUDIES)

110Behaviour change (2 studies): One of two controlled studies in Australia found that greater bilbies trained to avoid introduced predators showed more predator avoidance behaviour, the second study found no difference in behaviour between trained and untrained bilbies.

111Assessment: unknown effectiveness (effectiveness 40 %; certainty 30 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2580

Treat disease in wild mammals

112Three studies evaluated the effects on mammals of treating disease in the wild. Two studies were in the USA and one was in Germany.

113COMMUNITY RESPONSE (0 STUDIES)

114POPULATION RESPONSE (2 STUDIES)

115Condition (2 studies): A replicated study in Germany found that medical treatment of mouflons against foot rot disease healed most infected animals. A before-and-after study in the USA found that management which included vaccination of Yellowstone bison did not reduce prevalence of brucellosis. BEHAVIOUR (1 STUDY)

116Uptake (1 study): A study in the USA found that a molasses-based bait was readily consumed by white-tailed deer, including when it contained a dose of a disease vaccination.

117Assessment: unknown effectiveness (effectiveness 50 %; certainty 32 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2581

No evidence found (no assessment)

118We have captured no evidence for the following interventions:

  • Eliminate highly virulent diseases early in an epidemic by culling all individuals (healthy and infected) in a defined area

  • Sterilize non-native domestic or feral species (e.g. cats and dogs).

15.8.3 Other

Likely to be beneficial

Use fencing to exclude grazers or other problematic species

119Three studies evaluated the effects on mammals of using fencing to exclude grazers or other problematic species. One study was in each of the USA, Australia and Spain.

120COMMUNITY RESPONSE (1 STUDY)

121Richness/diversity (1 study): A controlled, before-and-after study in Australia found that after fencing to exclude introduced herbivores, native mammal species richness increased.

122POPULATION RESPONSE (3 STUDIES)

123Abundance (3 studies): Two controlled studies (including one replicated, paired sites study) in Spain and Australia found that using fences to exclude large or introduced herbivores increased the abundance of Algerian mice and native mammals. A replicated, paired sites study in the USA found that in areas fenced to exclude livestock grazing and off-road vehicles, abundance of black-tailed hares was lower compared to in unfenced areas.

124BEHAVIOUR (0 STUDIES)

125Assessment: likely to be beneficial (effectiveness 50 %; certainty 46 %; harms 10 %).

https://www.conservationevidence.com/​actions/​2495

Use fencing to exclude predators or other problematic species

126Ten studies evaluated the effects on mammals of using fencing to exclude predators or other problematic species. Four studies were in Australia, four were in the USA and two were in Spain.

127COMMUNITY RESPONSE (1 STUDY)

128Richness/diversity (1 study): A site comparison study in Australia found that fencing which excluded feral cats, foxes and rabbits increased small mammal species richness.

129POPULATION RESPONSE (10 STUDIES)

130Abundance (4 studies): Two of three studies (including two replicated, controlled studies), in Spain, Australia and the USA, found that abundances of European rabbits and small mammals were higher within areas fenced to exclude predators or other problematic species, compared to in unfenced areas. The third study found that hispid cotton rat abundance was not higher with predator fencing. A replicated, controlled study in Spain found that translocated European rabbit abundance was higher in fenced areas that excluded both terrestrial carnivores and raptors than in areas only accessible to raptors.

131Reproductive success (1 study): A replicated, controlled study in USA found that predator exclosures increased the number of white-tailed deer fawns relative to the number of adult females.

132Survival (7 studies): Four of six studies (including four replicated, controlled studies) in Spain, Australia and the USA, found that fencing to exclude predators did not increase survival of translocated European rabbits, hispid cotton rats, southern flying squirrels or western barred bandicoots. The other two studies found that persistence of populations of eastern barred bandicoots and long-haired rats was greater inside than outside fences. A controlled, before-and-after study in the USA found that electric fencing reduced coyote incursions into sites frequented by black-footed ferrets.

133BEHAVIOUR (0 STUDIES)

134Assessment: likely to be beneficial (effectiveness 50 %; certainty 50 %; harms 0 %).

https://www.conservationevidence.com/​actions/​2497

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