Meeting ultraviolet B radiation requirements of amphibians in captivity: A case study with mountain chicken frogs (Leptodactylus fallax) and general recommendations for pre-release health screening

Abstract

Conservation breeding programmes are a tool used to prevent amphibian extinctions. The husbandry requirements of amphibians are complex. Ongoing research is needed to ensure optimal management of those captive-bred animals destined, in particular, for reintroduction. The UV-B and vitamin D3 requirements of amphibians are largely unknown. Metabolic bone disease has been reported in a number of species. These include the Critically Endangered mountain chicken frog (Leptodactylus fallax) reared in captivity on diets supplemented with a high-calcium multivitamin and mineral supplement containing vitamin D3 but without UV-B provision. Captive-bred L. fallax being reared for reintroduction to Montserrat were provided with UV-B radiation from metamorphosis and were fed on insects supplemented with vitamins and minerals. Overlapping heat, light and UV-B gradients were provided, mimicking what we believe best represents the natural situation and thereby facilitated self-regulation of UV-B exposure. A subset of 10 frogs was periodically radiographed to assess skeletal health. Radiographic bone density and anatomical integrity appeared unremarkable when compared with a wild caught L. fallax. In addition to other routine health-screening, we recommend that radiography be performed to a structured schedule on a subset of all captive-bred and reared amphibians to assess skeletal health and to gauge the appropriateness of captive husbandry. We demonstrate here that, through the appropriate provision of a combination of both UV-B radiation and dietary supplementation, L. fallax can be bred and reared in captivity with healthy skeletal development.

Comparison of the nutritional content of the captive and wild diets of the critically endangered mountain chicken frog (Leptodactylus fallax) to improve its captive husbandry

“…The authors expected that the calcium content and calcium:phosphorus ratio would be low in the CDC as low calcium content has also been identified in previous analyses of captive feeder crickets and locusts (Barker et al, ; Finke, , ; Michaels, Antwis & Preziosi, ; Oonincx & Dierenfeld, ; Oonincx & van der Poel, ). King, Muhlbauer and James () found that low dietary calcium, combined with a lack of UV‐B lighting, was associated with the development of metabolic bone disease in captive L. fallax , although this is now rare since Tapley, Rendle et al () recommended routine dietary calcium supplementation and UV‐B provision. Methods to improve the calcium:phosphorus ratio of captive diet food items include supplementation of calcium by gut‐loading and dusting (Anderson, ; Michaels, Antwis et al, ).…”

Development of a body condition score for the mountain chicken frog (Leptodactylus fallax)

“…The BCS may therefore be advantageous over body condition indices based on mass and length as these two measures may be influenced by factors other than energy reserves such as age, sex, developmental stage, hydration status, gut fill, structural deformities, and reproductive status (MacCracken & Stebbings, ). However, scores assigned using the BCS would likely still be affected by major structural deformities of the key anatomical landmarks, for example, caused by trauma or metabolic bone disease, although the latter is no longer a common problem in the captive population as mountain chicken frogs are routinely fed a variety of invertebrates supplemented with a high‐calcium multivitamin and mineral supplement containing vitamin D 3 and provided with appropriate levels of UV‐B radiation (Tapley et al, ).…”

The tonic immobility test: Do wild and captive golden mantella frogs (Mantella aurantiaca) have the same response?

“…Persistent exposure to continuous stressors can have many deleterious consequences for captive animals putting at risk the long-term health of captive animals [23,36,41,42,43,44]. Environmental factors, such as providing the correct UV light standards, could be involved in maintaining the healthy state of frogs kept in captivity [32,45,46] The lack of UV light provision for the Mitsinjo colony could, also, be involved at the low body condition.…”

“…Some of the key behaviours affected by corticosterone in amphibians are defensive behaviours such as tonic immobility [18]. However, if frogs from Mitsinjo were already experiencing chronic levels of stress due to a poor diet and environment, it is possible that their acute stress responses could be blunted [46], such as TI responses.…”