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What Works in Conservation 2018

 | 
William J. Sutherland
, 
Lynn V. Dicks
, 
Nancy Ockendon
, 
et al.

1. Amphibian conservation

1.13 Species management

Texte intégral

1Strict protocols should be followed when carrying out these interventions to minimise potential spread of disease-causing agents such as chytrid fungi and Ranavirus.

1.13.1 Translocate amphibians

Likely to be beneficial

● Translocate amphibians (amphibians in general)

2Overall, three global reviews and one study in the USA found that 65% of amphibian translocations that could be assessed resulted in established breeding populations or substantial recruitment to the adult population. A further two translocations resulted in breeding and one in survival following release. One review found that translocations of over 1,000 animals were more successful, but that success was not related to the source of animals (wild or captive), life-stage, continent or reason for translocation. Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 19%).

3http://www.conservationevidence.com/​actions/​854

● Translocate amphibians (great crested newts)

4Four of six studies in the UK found that translocated great crested newts maintained or established breeding populations. One found that populations survived at least one year in 37% of cases, but one found that within three years breeding failed in 48% of ponds. A systematic review of 31 studies found no conclusive evidence that mitigation that included translocations resulted in self-sustaining populations. One review found that newts reproduced following 56% of translocations, in some cases along with other interventions. Assessment: likely to be beneficial (effectiveness 50%; certainty 50%; harms 10%).

5http://www.conservationevidence.com/​actions/​858

● Translocate amphibians (natterjack toads)

6Three studies in France and the UK found that translocated natterjack toad eggs, tadpoles, juveniles or adults established breeding populations at some sites, although head-started or captive-bred animals were also released at some sites. Re-establishing toads on dune or saltmarsh habitat was more successful than on heathland. One study in the UK found that repeated translocations of wild rather than captive-bred toads were more successful. Assessment: likely to be beneficial (effectiveness 60%; certainty 56%; harms 10%).

7http://www.conservationevidence.com/​actions/​859

● Translocate amphibians (salamanders including newts)

8Four studies in the UK and USA found that translocated eggs or adults established breeding populations of salamanders or smooth newts. One study in the USA found that one of two salamander species reproduced following translocation of eggs, tadpoles and metamorphs. One study in the USA found that translocated salamander eggs hatched and tadpoles had similar survival rates as in donor ponds. Assessment: likely to be beneficial (effectiveness 70%; certainty 55%; harms 0%).

9http://www.conservationevidence.com/​actions/​860

● Translocate amphibians (toads)

10Two of four studies in Denmark, Germany, the UK and USA found that translocating eggs and/or adults established common toad breeding populations. One found populations of garlic toads established at two of four sites and one that breeding populations of boreal toads were not established. One study in Denmark found that translocating green toad eggs to existing populations, along with habitat management, increased population numbers. Four studies in Germany, Italy, South Africa and the USA found that translocated adult toads reproduced, survived up to six or 23 years, or some metamorphs survived over winter. Assessment: likely to be beneficial (effectiveness 60%; certainty 56%; harms 10%).

11http://www.conservationevidence.com/​actions/​855

● Translocate amphibians (wood frogs)

12Two studies in the USA found that following translocation of wood frog eggs, breeding populations were established in 25–50% of created ponds. One study in the USA found that translocated eggs hatched and up to 57% survived as tadpoles in pond enclosures. Assessment: likely to be beneficial (effectiveness 40%; certainty 50%; harms 0%).

13http://www.conservationevidence.com/​actions/​856

Trade-off between benefit and harms

● Translocate amphibians (frogs)

14Eight of ten studies in New Zealand, Spain, Sweden, the UK and USA found that translocating frog eggs, juveniles or adults established breeding populations. Two found that breeding populations went extinct within five years or did not establish. Five studies in Canada, New Zealand and the USA found that translocations of eggs, juveniles or adults resulted in little or no breeding at some sites. Five studies in Italy, New Zealand and the USA found that translocated juveniles or adults survived the winter or up to eight years. One study in the USA found that survival was lower for Oregon spotted frogs translocated as adults compared to eggs. Two studies in the USA found that 60–100% of translocated frogs left the release site and 35–73% returned to their original pond within 32 days. Two studies in found that frogs either lost or gained weight after translocation. Assessment: trade-offs between benefits and harms (effectiveness 58%; certainty 65%; harms 20%).

15http://www.conservationevidence.com/​actions/​861

1.13.2 Captive breeding, rearing and releases

Likely to be beneficial

● Release captive-bred individuals (amphibians in general)

16One review found that 41% of release programmes of captive-bred or head-started amphibians showed evidence of breeding in the wild for multiple generations, 29% showed some evidence of breeding and 12% evidence of survival following release. Assessment: likely to be beneficial (effectiveness 55%; certainty 50%; harms 10%).

17http://www.conservationevidence.com/​actions/​871

● Release captive-bred individuals (frogs)

18Five of six studies in Europe, Hong Kong and the USA found that captive-bred frogs released as tadpoles, juveniles or adults established breeding populations and in some cases colonized new sites. Three studies in Australia and the USA found that a high proportion of frogs released as eggs survived to metamorphosis, some released tadpoles survived the first few months, but few released froglets survived. Four studies in Australia, Italy, the UK and USA found that captive-bred frogs reproduced at 31–100% of release sites, or that breeding was limited. Assessment: likely to be beneficial (effectiveness 60%; certainty 60%; harms 15%).

19http://www.conservationevidence.com/​actions/​870

Trade-off between benefit and harms

● Breed amphibians in captivity (frogs)

20Twenty-three of 33 studies across the world found that amphibians produced eggs in captivity. Seven found mixed results, with some species or populations reproducing successfully, but with other species difficult to maintain or raise to adults. Two found that frogs did not breed successfully or died in captivity. Seventeen of the studies found that captive-bred frogs were raised successfully to hatching, tadpoles, froglets or adults in captivity. Four studies in Canada, Fiji, Hong Kong and Italy found that 30–88% of eggs hatched, or survival to metamorphosis was 75%, as froglets was 17–51% or to adults was 50–90%. Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 68%; harms 30%).

21http://www.conservationevidence.com/​actions/​835

● Breed amphibians in captivity (harlequin toads)

22Four of five studies in Colombia, Ecuador, Germany and the USA found that harlequin toads reproduced in captivity. One found that eggs were only produced by simulating a dry and wet season and one found that breeding was difficult. One found that captive-bred harlequin toads were raised successfully to metamorphosis in captivity and two found that most toads died before or after hatching. Assessment: trade-offs between benefits and harms (effectiveness 44%; certainty 50%; harms 28%).

23http://www.conservationevidence.com/​actions/​836

● Breed amphibians in captivity (Mallorcan midwife toad)

24Two studies in the UK found that Mallorcan midwife toads produced eggs that were raised to metamorphs or toadlets in captivity. However, clutches dropped by males were not successfully maintained artificially. One study in the UK found that toads bred in captivity for nine or more generations had slower development, reduced genetic diversity and predator defence traits. Assessment: trade-offs between benefits and harms (effectiveness 69%; certainty 55%; harms 40%).

25http://www.conservationevidence.com/​actions/​837

● Breed amphibians in captivity (salamanders including newts)

26Four of six studies in Japan, Germany, the UK and USA found that eggs were produced successfully in captivity. Captive-bred salamanders were raised to yearlings, larvae or adults. One review found that four of five salamander species bred successfully in captivity. Four studies in Germany, Mexico and the USA found that egg production, larval development, body condition and survival were affected by water temperature, density or enclosure type. Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 50%; harms 25%).

27http://www.conservationevidence.com/​actions/​838

● Breed amphibians in captivity (toads)

28Ten studies in Germany, Italy, Spain, the UK and USA found that toads produced eggs in captivity. Eight found that toads were raised successfully to tadpoles, toadlets or adults in captivity. Two found that most died after hatching or metamorphosis. Two reviews found mixed results with four species of toad or 21% of captive populations of Puerto Rican crested toads breeding successfully. Four studies in Germany, Spain and the USA found that reproductive success was affected by tank location and humidity. Assessment: trade-offs between benefits and harms (effectiveness 65%; certainty 60%; harms 25%).

29http://www.conservationevidence.com/​actions/​848

● Head-start amphibians for release

30Twenty-two studies head-started amphibians from eggs and monitored them after release. A global review and six of 10 studies in Europe and the USA found that released head-started tadpoles, metamorphs or juveniles established breeding populations or increased existing populations. Two found mixed results with breeding populations established in 71% of studies reviewed or at 50% of sites. Two found that head-started metamorphs or adults did not establish a breeding population or prevent a population decline. An additional 10 studies in Australia, Canada, Europe and the USA measured aspects of survival or breeding success of released headstarted amphibians and found mixed results. Three studies in the USA only provided results for head-starting in captivity. Two of those found that eggs could be reared to tadpoles, but only one successfully reared adults. Assessment: trade-offs between benefits and harms (effectiveness 60%; certainty 60%; harms 25%).

31http://www.conservationevidence.com/​actions/​881

● Release captive-bred individuals (Mallorcan midwife toad)

32Three studies in Mallorca found that captive-bred midwife toads released as tadpoles, toadlets or adults established breeding populations at 38–100% of sites. One study in the UK found that predator defences were maintained, but genetic diversity was reduced in a captive-bred population. Assessment: trade-offs between benefits and harms (effectiveness 68%; certainty 58%; harms 20%).

33http://www.conservationevidence.com/​actions/​873

● Release captive-bred individuals (toads)

34Two of three studies in Denmark, Sweden and the USA found that captive-bred toads released as tadpoles, juveniles or metamorphs established populations. The other found that populations were not established. Two studies in Puerto Rico found that survival of released captive-bred Puerto Rican crested toads was low. Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 50%; harms 20%).

35http://www.conservationevidence.com/​actions/​875

● Use artificial fertilization in captive breeding

36Three replicated studies, including two randomized studies, in Australia and the USA found that the success of artificial fertilization depended on the type and number of doses of hormones used to stimulate egg production. One replicated study in Australia found that 55% of eggs were fertilized artificially, but soon died. Assessment: trade-offs between benefits and harms (effectiveness 40%; certainty 40%; harms 20%).

37http://www.conservationevidence.com/​actions/​834

● Use hormone treatment to induce sperm and egg release

38One review and nine of 10 replicated studies, including two randomized, controlled studies, in Austria, Australia, China, Latvia, Russia and the USA found that hormone treatment of male amphibians stimulated or increased sperm production, or resulted in successful breeding. One found that hormone treatment of males and females did not result in breeding. One review and nine of 14 replicated studies, including six randomized and/or controlled studies, in Australia, Canada, China, Ecuador, Latvia and the USA found that hormone treatment of female amphibians had mixed results, with 30–71% of females producing viable eggs following treatment, or with egg production depending on the combination, amount or number of doses of hormones. Three found that hormone treatment stimulated egg production or successful breeding. Two found that treatment did not stimulate or increase egg production. Assessment: trade-offs between benefits and harms (effectiveness 50%; certainty 65%; harms 30%).

39http://www.conservationevidence.com/​actions/​883

Unknown effectiveness (limited evidence)

● Release captive-bred individuals (salamanders including newts)

40One study in Germany found that captive-bred great crested newts and smooth newts released as larvae, juveniles and adults established stable breeding populations. Assessment: unknown effectiveness — limited evidence (effectiveness 70%; certainty 30%; harms 0%).

41http://www.conservationevidence.com/​actions/​874

Unlikely to be beneficial

● Freeze sperm or eggs for future use

42Ten replicated studies, including three controlled studies, in Austria, Australia, Russia, the UK and USA found that following freezing, viability of amphibian sperm, and in one case eggs, depended on species, cryoprotectant used, storage temperature or method and freezing or thawing rate. One found that sperm could be frozen for up to 58 weeks. Assessment: unlikely to be beneficial (effectiveness 35%; certainty 50%; harms 10%).

43http://www.conservationevidence.com/​actions/​876

Likely to be ineffective or harmful

● Release captive-bred individuals (green and golden bell frogs)

44Three studies in Australia found that captive-bred green and golden bell frogs released mainly as tadpoles did not established breeding populations, or only established breeding populations in 25% of release programmes. One study in Australia found that some frogs released as tadpoles survived at least 13 months. Assessment: likely to be ineffective or harmful (effectiveness 20%; certainty 50%; harms 20%).

45http://www.conservationevidence.com/​actions/​872

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