Muñoz-Saravia, A., G. Callapa & G. P. J. Janssens

Prey selection and dietary nutrient composition of an endangered amphibian, the Titicaca water frog (Telmatobius culeus). pp. 171-183 plus Supplementary material.

Abstract. It is important to understand the foraging strategies of an endangered species, in this way to evaluate the possible consequences of ecological changes. This study describes the availability of food resources for the Endangered Titicaca water frog Telmatobius culeus in one locality in Titicaca Lake and shows how potential prey abundance can be affected by season or depth of water. Insights about the diet composition and prey selection are provided together with nutritional information of its potential prey items. Substrate traps were installed during different seasons and different depths to collect potential prey items, gut content analysis was carried out in 44 frogs and nutritional properties of potential prey items was obtained. Thirteen species of potential prey items were recorded. For some of the species such as Hyalella spp., Heleobia sp. and Biomphalaria sp., the data indicated a seasonal and spatial variation of the prey items. Amphipod Hyalella spp. and snails Heleobia sp. and Biomphalaria sp. were the main prey items consumed by frogs. Diet did not differ between males and females. The diet of small frogs was dominated by Hyalella spp., in contrast to the diet of large frogs which consumed a greater diversity of prey types. Telmatobius culeus selected Heleobia sp. from all the available prey items from its environment. Calcium:phosphorus ratios, that when inverse can contribute to metabolic bone disease, were high in Hyalella spp. but this prey item was relatively low in crude protein and gross energy compared with other species besides Heleobia sp. and Biomphalaria sp. This study provides ecological information about Telmato­bius culeus that can be useful for in-situ and ex-situ conservation efforts: (1) the identification of prey items will allow monitoring and eventually managing the ecosystem, (2) it indicates which prey items need to be cultured in captivity, and (3) how captive diets should be adapted to optimally mimic the natural diet of Telmatobius culeus.

Key words. Amphibia, Anura, Telmatobiidae, foraging strategies, prey availability, habitat, season, gut content.