Relying on a Single Anuran Species: Feeding Ecology of a Snake Community on Kinkasan Island, Miyagi Prefecture, Japan

Abstract

Feeding habits of snakes on Kinkasan Island, where potential food resources for snakes is limited, was investigated based on field surveys of six years. In total 280 snakes, which consisted of five species (Elaphe quadrivirgata, E. climacophora, Euprepiophis conspicillatus, Rhabdophis tigrinus, and Gloydius blomhoffii), were collected. A total of 168 prey items were recovered from the stomach contents of these snakes. The diet of R. tigrinus and G. blomhoffii exclusively consisted of a frog, Rana tagoi, which is the only amphibian species inhabiting Kinkasan Island. Diet of El. quadrivirgata was also predominantly comprised of Ra. tagoi (97.7%). Only endothermic animals were found in the stomach contents of El. climacophora and Eu. conspicillatus. Direct observations of feeding behavior and a broad range of body temperature of El. quadrivirgata indicated that during the breeding season of Ra. tagoi, this snake forages for frogs hiding in crevices of rocks immersed in cold running water of mountain streams. Our study demonstrated that, given the limited prey fauna on Kinkasan Island, two dietary generalists, El. quadrivirgata and G. blomhoffii, and one amphibian specialist, R. tigrinus, largely rely on the single frog species as major diet. High exploitation of Ra. tagoi by El. quadrivirgata would be attained by its unique foraging tactics that are characterized by a shuttling movement between hot basking rocks and cold streams for foraging.