Feeding in anuran communities on islands in the Danube floodplain

Abstract

Feeding habits and food choice of anurans found on two islands in the lower Danube floodplain were studied for two years. The five most abundant anuran species included in this study were Bombina bombina, Hyla arborea, Pelobates fuscus, Rana esculenta and R. ridibunda. In B. bombina the niche breadths of young and adults were of similar magnitude and the degree of overlap between these size classes was high. In Rana esculenta complex young individuals had a much broader trophic niche than adults. A low degree of overlap existed between young and adults, suggesting that the various size classes exploit different segments of the prey resource. Overall, species with a larger size range consumed a higher prey diversity. Prey occurrence was sampled throughout the study on a regular basis. The analysis of selectivity in feeding using Ivlev's index showed that the prey taxa that appeared to be preferred were generally rare in the environment. Detrended Correspondence Analysis revealed that the composition of anuran diets were highly overlapping but differed from the composition of the resource base. The trophic resource was highly partitioned in space and time and thus allowed the coexistence of large populations with similar diets.