The diet of Rana temporaria Linnaeus, 1758 in relation to prey availability near its altitudinal limit

The diet of Rana temporaria (Linnaeus, 1758) was studied in the Gran Paradiso National Park, at and above the local timberline, up to the upper limit of its altitudinal distribution. A total of 128 adult frogs (length range: 3.7-9.0 cm) were captured from 2010 to 2012. Stomach content from 46 individuals was obtained by stomach flushing, of which 66% of the stomachs were empty. The diet composition was compared with the composition of the ground-dwelling invertebrate community, sampled by pitfall trapping. The number of prey items in the stomachs was lower at higher altitude and during the breeding season, when most of the stomachs were empty. R. temporaria feeds on a large number of taxa (in order of abundance: Coleoptera, Diptera, Hymenoptera, Opiliones, Araneae, Lepidoptera, Plecoptera, Trichoptera, Orthoptera, Acarina and Chilopoda), including a single observation of cannibalism on a freshly metamorphosed frog. There is a strong similarity between prey composition and availability. Therefore, near its altitudinal limit, Rana temporaria shows a generalist and slightly selective predatory behavior.