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

Abstract

It is vital to provide appropriate nutrition to maintain healthy populations in conservation breeding programs. Knowledge of the wild diet of a species can be used to inform captive diet formulation. The nutritional content of the wild diet of the critically endangered mountain chicken frog (Leptodactylus fallax) is unknown, like that of most amphibians. In this study, we analyzed the nutritional content of food items that comprise 91% of the wild diet of L. fallax, by dry weight of food items, and all food items offered to captive L. fallax at ZSL London Zoo and Jersey Zoo. We subsequently compared the nutritional content of the wild diet and captive diet at ZSL London Zoo consumed by L. fallax. To the authors' knowledge, this is the first study to directly compare the nutritional content of the wild and captive diets of an anuran amphibian. The captive diet at ZSL London Zoo, without dusting of nutritional supplements, was higher in gross energy and crude fat and lower in ash, calcium and calcium:phosphorus ratio than the wild diet. Most of the food items in the captive diets had a high omega-6:omega-3 fatty acid ratio and in the wild diet had a low omega-6:omega-3 fatty acid ratio. We recommend a combination of modifications to the captive diets to better reflect the nutritional content of the wild diet. Nutritional analysis of captive and wild diets is recommended for other species in conservation breeding programs to improve captive husbandry and ultimately fitness.

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

“…On day 200, at approximately 1 year old, the animals were combined in a single enclosure with the same conditions as the parents (Enclosure Type 1, Table 1) although not co-housed with them. Animals were fed a varied diet following Jayson et al (2018a). All feeds for adults and pre-experimental juveniles were supplemented with a 1:1 by weight mix of Vetark Nutrobal® (VETARK Professional, Winchester, UK) and powdered calcium carbonate (product code P0302, Cambridge Commodities, Cambridge, UK), which was dusted onto prey items (Michaels et al, 2014b).…”

“…It has been the focus of well-rounded research and conservation activity in-and ex-situ (Adams et al, 2014;Tapley et al, 2014). Outputs include description and quantification of population trends (Hudson et al, 2016a), disease dynamics and mitigation (Hudson et al, 2016b;Hudson et al, 2019), translocation attempts in the field (Adams et al, 2014), local cultural associations (Nicholson et al, 2020), life history and reproductive data (Gibson et al, 2004), the development of field methods, captive husbandry protocols (Nicholson et al, 2017;Jameson et al, 2019) and the empirical quantification of some of the requirements of this species in captivity from captive populations (Tapley et al, 2015b;Jayson et al, 2018a;. Importantly, these data streams have been derived from co-ordinated approaches between captive and field components, in line with the One Plan Approach of the IUCN Conservation Planning Specialist Group; however, there is much work to be done to optimise captive husbandry protocols.…”

“…The provision of adequate nutrition is a current challenge in amphibian husbandry (Dugas et al, 2013;Gagliardo et al, 2008;Antwis & Browne, 2009;King et al, 2011;Verschooren et al, 2011;Ogilvy et al, 2012;Michaels et al, 2014b;. The physiological requirements of most amphibians for a suite of different nutrients are unknown (Jayson et al, 2018a) and only a narrow range of prey items are available to feed captive https://doi.org/10. 33256/31.1.1826 amphibians (Michaels et al, 2014b).…”

“…Calcium metabolism is a case in point as it relies on the appropriate replication of sunlight (specifically UVB radiation and heat) and the provision of dietary calcium, phosphorus and vitamin D3 sources in appropriate amounts and combinations (Antwis & Browne, 2009;Baines et al, 2016). This is further complicated by the tendency for commercially raised invertebrate species to be calcium-deficient in both absolute terms and relative to phosphorus content (Barker et al, 1998;Finke et al, 2002;Jayson et al, 2018a). In L. fallax, comparison of wild and captive diets (Jayson et al, 2018a) and empirical refinement of UVB provision (Tapley et al, 2015b) have demonstrated that supplementation of diets with calcium along with appropriate provision of UVB lighting is important to meet the needs of the species in captivity.…”

“…This is further complicated by the tendency for commercially raised invertebrate species to be calcium-deficient in both absolute terms and relative to phosphorus content (Barker et al, 1998;Finke et al, 2002;Jayson et al, 2018a). In L. fallax, comparison of wild and captive diets (Jayson et al, 2018a) and empirical refinement of UVB provision (Tapley et al, 2015b) have demonstrated that supplementation of diets with calcium along with appropriate provision of UVB lighting is important to meet the needs of the species in captivity. However, empirical data regarding the optimal amount of supplementation are lacking, and the complexity of factors influencing calcium metabolism precludes simple replication of wild diets (see Michaels et al, 2014b;.…”