The effects of two calcium supplementation regimens on growth and health traits of juvenile mountain chicken frogs (Leptodactylus fallax)

Abstract

The mountain chicken frog (Leptodactylus fallax) is among the 42 % of amphibians threatened with extinction and is dependent upon ex situ populations to recover in the wild. Amphibian captive husbandry is not fully understood and empirical data are required to optimise protocols for each species in captivity. Calcium metabolism and homeostasis are areas of importance in captive husbandry research and have been identified as a challenge in maintaining ex situ populations of L. fallax. We trialled two frequencies (twice and seven times weekly) of calcium supplementation via dusting of feeder insects in two groups of L. fallax juveniles and measured growth and health effects through morphometrics, radiography, ultrasonography and blood and faecal analysis over 167 days, followed by a further 230 days of monitoring on an intermediate diet informed by the initial dataset. We showed that supplementation treatment did not affect growth or health status as measured through blood analysis, radiography and ultrasonography. More frequent supplementation resulted in significantly more radiopaque endolymphatic sacs and broader skulls. Frogs fed more calcium excreted twice as much calcium in their faeces. The intermediate diet resulted in previously lower supplementation frogs approximating the higher supplementation frogs in morphometrics and calcium stores. Comparison with radiographic data from wild frogs showed that both treatments may still have had narrower skulls than wild animals, but mismatching age class may limit this comparison. Our data may be used to inform dietary supplementation of captive L. fallax as well as other amphibians.

Activity budgets, responses to disturbance and novel behaviours in captive mountain chicken frogs Leptodactylus fallax

“…Furnishings consisted of leaf litter, 2 x large artificial palm leaves, 2 x clay-lined nest boxes with tubes for entrance. Detailed husbandry information is given by Michaels et al (2021). Animals were fed three times a week, but food insects were almost always present in dens between feedings, as frogs do not capture all items immediately.…”

“…Observations occurred between the hours of 1700 and 0830 the next day. Lights (full spectrum specialist lighting arrays -see Michaels et al, 2021 for details) within the dens were on until 1800 after which they remained switched off until 0745 the following morning.…”

“…Although successful captive breeding has led to an increase in this captive population size (Jameson et al, https://doi.org/10.33256/33.2.4354 2019), managing mountain chickens in captivity has proven problematic, mainly due to the highly specific conditions required by this species in captivity (Tapley et al, 2015;Donaldson, 2019;Jameson et al, 2019). The physiological requirements of captive mountain chickens are becoming better understood (Fitzgerald et al, 2007;Dierenfeld et al, 2008;King et al, 2011;Jaffe et al, 2015;Tapley et al, 2015;Jayson et al, 2018;2018b;Croci et al, 2019;Donaldson, 2019;Jameson et al, 2019;Ashpole et al, 2021;Michaels et al, 2021;White et al, 2021). Although very basic information on habitat use and activity patterns is known from wild populations (Schwartz & Henderson, 1991;Daltry, 2002; see Jameson et al, 2019), detailed information on activity budgets and patterns is lacking for both wild and captive mountain chickens.…”

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“…Until the threat of emerging infectious disease can be ameliorated, a bio-secure, captive metapopulation has been established in European zoos, alongside a non-biosecure population from the same gene pool, with the aims of producing viable stock for future translocation purposes, as well as for research and public engagement initiatives (e.g. Tapley et al, 2015;Jayson et al, 2018a,b;Michaels et al, 2021). Captive breeding success and translocation planning requires further life history data to inform refinement and to tackle current limitations (Jameson et al, 2019) and for this reason, it is important to document new information when unique observations are made.…”