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What Works in Conservation 2018

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

9. Management of captive animals

9.1. Ex-situ conservation–breeding amphibians

Texte intégral

9.1.1 Refining techniques using less threatened species

Unknown effectiveness (limited evidence)

● Identify and breed a similar species to refine husbandry techniques prior to working with target species

1Two small, replicated interlinked studies in Brazil found that working with a less threatened surrogate species of frog first to establish husbandry interventions promoted successful breeding of a critically endangered species of frog. Assessment: unknown effectiveness (effectiveness 68%; certainty 30%; harms 15%).

2https://www.conservationevidence.com/​actions/​1862

9.1.2 Changing environmental conditions/microclimate

Unknown effectiveness (limited evidence)

● Vary enclosure temperature to simulate seasonal changes in the wild

3One small, replicated study in Italy found that one of six females bred following a drop in temperature from 20-24 to 17°C, and filling of an egg laying pond. One replicated, before-and-after study in 2006-2012 in Australia found that providing a pre-breeding cooling period, alongside allowing females to gain weight before the breeding period, along with separating sexes during the non-breeding period, providing mate choice for females and playing recorded mating calls, increased breeding success. Assessment: unknown effectiveness (effectiveness 50%; certainty 35%; harms 0%).

4https://www.conservationevidence.com/​actions/​1864

● Vary quality or quantity (UV% or gradients) of enclosure lighting to simulate seasonal changes in the wild

5One replicated study in the UK found that there was no difference in clutch size between frogs given an ultraviolet (UV) boost compared with those that only received background levels. However, frogs given the UV boost had a significantly greater fungal load than frogs that were not UV-boosted. Assessment: unknown effectiveness (effectiveness 0%; certainty 33%; harms 20%).

6https://www.conservationevidence.com/​actions/​1865

● Provide artificial aquifers for species which breed in upwelling springs

7One small study in the USA found that salamanders bred in an aquarium fitted with an artificial aquifer. Assessment: unknown effectiveness (effectiveness 50%; certainty 15%; harms 0%).

8https://www.conservationevidence.com/​actions/​1871

● Vary artificial rainfall to simulate seasonal changes in the wild

9Two replicated, before-and-after studies in Germany and Austria found that simulating a wet and dry season, as well as being moved to an enclosure with more egg laying sites and flowing water in Austria, stimulated breeding and egg deposition. In Germany, no toadlets survived past 142 days old. Assessment: unknown effectiveness (effectiveness 78%; certainty 33%; harms 0%).

10https://www.conservationevidence.com/​actions/​1872

No evidence found (no assessment)

11We have captured no evidence for the following interventions:

  • Vary enclosure humidity to simulate seasonal changes in the wild using humidifiers, foggers/misters or artificial rain
  • Vary duration of enclosure lighting to simulate seasonal changes in the wild
  • Simulate rainfall using sound recordings of rain and/or thunderstorms
  • Allow temperate amphibians to hibernate
  • Allow amphibians from highly seasonal environments to have a period of dormancy
  • Vary water flow/speed of artificial streams in enclosures for torrent breeding species

9.1.3 Changing enclosure design for spawning or egg laying sites

Unknown effectiveness (limited evidence)

● Provide multiple egg laying sites within an enclosure

12One replicated study in Australia found that frogs only bred once moved into an indoor enclosure which had various types of organic substrate, allowed temporary flooding, and enabled sex ratios to be manipulated along with playing recorded mating calls. One small, replicated, before-and-after study in Fiji found that adding rotting logs and hollow bamboo pipes to an enclosure, as well as a variety of substrates, promoted egg laying in frogs. Assessment: unknown effectiveness (effectiveness 50%; certainty 25%; harms 0%).

13https://www.conservationevidence.com/​actions/​1873

● Provide natural substrate for species which do not breed in water (e.g. burrowing/tunnel breeders)

14Two replicated studies in Australia and Fiji found that adding a variety of substrates to an enclosure, as well as rotting logs and hollow bamboo pipes in one case, promoted egg laying of frogs. The Australian study also temporarily flooded enclosures, manipulated sex ratios and played recorded mating calls. Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).

15https://www.conservationevidence.com/​actions/​1874

Provide particular plants as breeding areas or egg laying sites

16One small, controlled study in the USA found that salamanders bred in an aquarium heavily planted with java moss and swamp-weed. Assessment: unknown effectiveness (effectiveness 75%; certainty 20%; harms 0%).

17https://www.conservationevidence.com/​actions/​1875

9.1.4 Manipulate social conditions

Unknown effectiveness (limited evidence)

● Manipulate sex ratio within the enclosure

18One replicated study in Australia found that frogs only bred once sex ratios were manipulated, along with playing recorded mating calls and moving frogs into an indoor enclosure which allowed temporary flooding, and had various types of organic substrate. Assessment: unknown effectiveness (effectiveness 35%; certainty 15%; harms 0%).

19https://www.conservationevidence.com/​actions/​1879

● Separate sexes in non-breeding periods

20One replicated, before-and-after study in Australia found that clutch size of frogs increased when sexes were separated in the non-breeding periods, alongside providing female mate choice, playing recorded mating calls and allowing females to increase in weight before breeding. Assessment: unknown effectiveness (effectiveness 65%; certainty 30%; harms 0%).

21https://www.conservationevidence.com/​actions/​1880

● Play recordings of breeding calls to simulate breeding season in the wild

22One replicated study in Australia found that frogs only bred when recorded mating calls were played, as well as manipulating the sex ratio after frogs were moved into an indoor enclosure that allowed temporary flooding and had various types of organic substrates. One replicated, before-and-after study in Australia found that clutch size of frogs increased when playing recorded mating calls, along with the sexes being separated in the nonbreeding periods, providing female mate choice, and allowing females to increase in weight before breeding. Assessment: unknown effectiveness (effectiveness 35%; certainty 28%; harms 0%).

23https://www.conservationevidence.com/​actions/​1881

● Allow female mate choice

24One replicated study in Australia found that frogs only bred after females carrying eggs were introduced to males, sex ratios were manipulated, recorded mating calls were played, and after being moved to an indoor enclosure which allowed temporary flooding and had various types of organic substrates.

25One replicated, before-and-after study in Australia found that clutch size of frogs increased when female mate choice was provided, alongside playing recorded mating calls, sexes being separated in the non-breeding periods, and allowing females to increase in weight before breeding. Assessment: unknown effectiveness (effectiveness 50%; certainty 20%; harms 0%).

26https://www.conservationevidence.com/​actions/​1882

No evidence found (no assessment)

27We have captured no evidence for the following interventions:

  • Provide visual barriers for territorial species
  • Manipulate adult density within the enclosure.

9.1.5 Changing the diet of adults

Unknown effectiveness (limited evidence)

● Supplement diets with carotenoids (including for colouration)

28One study in the USA found that adding carotenoids to fruit flies fed to frogs reduced the number of clutches, but increased the number of tadpoles and successful metamorphs. Assessment: unknown effectiveness (effectiveness 70%; certainty 28%; harms 0%).

29https://www.conservationevidence.com/​actions/​1887

● Increase caloric intake of females in preparation for breeding

30One replicated, before-and-after study in Australia found that clutch size of frogs increased when females increased in weight before breeding, as well as having mate choice, recorded mating calls, and sexes being separated during the non-breeding periods. Assessment: unknown effectiveness (effectiveness 60%; certainty 23%; harms 0%).

31https://www.conservationevidence.com/​actions/​1888

No evidence found (no assessment)

32We have captured no evidence for the following interventions:

  • Vary food provision to reflect seasonal availability in the wild
  • Formulate adult diet to reflect nutritional composition of wild foods
  • Supplement diets with vitamins/calcium fed to prey (e.g. prey gut loading)
  • Supplement diets with vitamins/calcium applied to food (e.g. dusting prey).

9.1.6 Manipulate rearing conditions for young

Trade-off between benefit and harms

● Manipulate temperature of enclosure to improve development or survival to adulthood

33One replicated study in Spain found that salamander larvae had higher survival rates when reared at lower temperatures. One replicated study in Germany found that the growth rate and development stage reached by harlequin toad tadpoles was faster at a higher constant temperature rather than a lower and varied water temperature. One replicated study in Australia found that frog tadpoles took longer to reach metamorphosis when reared at lower temperatures. One replicated, controlled study in Iran found that developing eggs reared within a temperature range of 12-25°C had higher survival rates, higher growth rates and lower abnormalities than those raised outside of that range. Assessment: trade-offs between benefits and harms (effectiveness 80%; certainty 58%; harms 20%).

34https://www.conservationevidence.com/​actions/​1893

Unknown effectiveness (limited evidence)

● Formulate larval diets to improve development or survival to adulthood

35One randomized, replicated, controlled study in the USA found that tadpoles had higher body mass and reached a more advanced developmental stage when fed a control diet (rabbit chow and fish food) or freshwater algae, compared to those fed pine or oak pollen. One randomized, replicated study in Portugal found that tadpoles reared on a diet containing 46% protein had higher growth rates, survival and body weights at metamorphosis compared to diets containing less protein. Assessment: unknown effectiveness (effectiveness 65%; certainty 35%; harms 0%).

36https://www.conservationevidence.com/​actions/​1889

● Manipulate larval density within the enclosure

37One randomized study in the USA found that decreasing larval density of salamanders increased larvae survival and body mass. Assessment: unknown effectiveness (effectiveness 88%; certainty 28%; harms 0%).

38https://www.conservationevidence.com/​actions/​1894

No evidence found (no assessment)

39We have captured no evidence for the following interventions:

  • Leave infertile eggs at spawn site as food for egg-eating larvae
  • Manipulate humidity to improve development or survival to adulthood
  • Manipulate quality and quantity of enclosure lighting to improve development or survival to adulthood
  • Allow adults to attend their eggs.

9.1.7 Artificial reproduction

No evidence found (no assessment)

40We have captured no evidence for the following interventions:

41• Use artificial cloning from frozen or fresh tissue

42For summarised evidence for

  • Use hormone treatment to induce sperm and egg release
  • Use artificial fertilization in captive breeding

43See Smith, R. K. and Sutherland, W. J. (2014) Amphibian Conservation: Global Evidence for the Effects of Interventions. Exeter, Pelagic Publishing.

44Key messages and summaries are available here:

45https://www.conservationevidence.com/​actions/​834

46https://www.conservationevidence.com/​actions/​883

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