Thanks to our trustee Prof. Roger Downie, from The University of Glasgow for this months Croaking Science article.
January’s ‘Croaking science’ summarised Dawson et al.’s (2016) report on amphibian species held in zoos worldwide. They found only 6.2% of globally threatened amphibian species held in zoos in 2014, compared with 15.9% of birds, 23% of mammals and 38% of reptiles, despite the fact that overall, amphibians are the most threatened of these groups. Even the 6.2% figure may be optimistic, since the research did not assess the viability and sustainability of the populations held. The Amphibian Conservation Action Plan (ACAP) developed by IUCN’s Amphibian Specialist Group (Gascon et al. 2007) regarded ex situ captive breeding programmes for threatened species as a crucial part of the Plan, and the Amphibian Ark (AArk) was founded to co-ordinate and promote this activity (Pavajeau et al. 2008). However, given the modest number of threatened species with established ex situ breeding programmes almost a decade into the ACAP, we need to take a realistic look at the capacity of zoos to meet the need…and to examine the alternatives.
Most adult amphibians are small animals, compared, say, with charismatic mammals such as big cats, so their space needs are modest and therefore relatively cheap. However, in other ways, amphibians are problematic for zoos. Most species are nocturnal, so are inactive when visitors come by, not good for attracting people to visit the zoo, and therefore explaining the popularity in zoos of the colourful and day-active poison arrow frogs, irrespective of their conservation status. Another problem is their reproductive potential; many amphibian species produce hundreds or thousands of eggs at a time, so once a zoo has succeeded in encouraging a pair to breed, it may soon be faced with the need to house hundreds of young, first as tadpoles, later as juveniles and adults. Then there is food; most adult amphibians eat only live food, mainly insects, but for most threatened species, it is not known whether they have any special dietary needs, and it may take some time to discover that though individuals survive and grow on a diet of easily provided insects such as crickets, they do not thrive reproductively. Research shows that micronutrients such as carotenoids can be crucial to the development of reproductive success (Ogilvy et al. 2012) but this work has been done on few species so far. And then there is behaviour: there is a common misconception that amphibian behaviour is essentially instinctual, fixed and inflexible, with little learning involved. However, research has shown that at least some amphibians show complex learning, including the marking out and defence of territories and the ability to navigate home after complex journeys through forest (Pasukonis et al. 2015). This widespread misconception has led to the view that the behavioural needs of amphibians in captivity need little consideration, as distinct from birds and mammals where zookeepers have long accepted the need for what is known as behavioural and environmental enrichment if animals are to be kept in good psychological health. Enrichment involves the design of enclosures where animals are encouraged to lead the active and complex lives that they would have in nature. As Michaels et al.(2014) found, there has been remarkably little investigation so far of enrichment provision for amphibians; they reviewed a few reports of different ways to provide food, that encouraged active foraging, and limited research on the impact of different enclosure furnishings, but little else. Enrichment is regarded as important in birds and mammals both on welfare grounds and in the context of ex situ conservation which aims to release captive bred animals to the wild. This aim can only succeed if the animals are capable of surviving and reproducing in the wild and this requires the acquisition of learned survival skills. There is no reason to expect the successful captive breeding/release of amphibians to lack these requirements.
All in all, we lack knowledge of both the physiological and behavioural needs of many of the most threatened amphibian species. Zoos can be places where these needs can be researched, but more emphasis is needed on such investigations. Are there alternatives to ex situ conservation in the battle to avoid further amphibian extinctions? Look out for further ‘Croaking Science’ articles.
Dawson,J. et al.(2016) Assessing the global zoo response to the amphibian crisis through 20-year trends in captive collections. Conservation Biology (already published on-line)
Gascon, C. et al.(2007) Amphibian conservation action plan. IUCN/SSC amphibian specialist group. Gland, Switzerland
Michaels, C. et al.(2014) The importance of enrichment for advancing amphibian welfare and conservation goals; a review of a neglected topic. Amphibian and Reptile Conservation 8, 7-23
Ogilvy,V. et al.(2012) A brighter future frogs? The influence of carotenoids on the health, development and reproductive success of the red eye tree frog. Animal Conservation 15, 480-488
Pasukonis, A. et al.(2015) Poison frogs rely on experience to find the way home in the rainforest. Biology Letters 10, 20140642
Pavajeau, l. et al.(2008) Amphibian Ark and the Year of the Frog campaign. International Zoo Yearbook 42, 24-29