Abstract
We surveyed stomach contents of Rana japonica on the forest floor of a hill in Northern Yokohama, Japan. The frogs preyed mainly on macro soil animals and insects throughout the active season. A difference in prey items was found between adult and juvenile frogs; i.e., adult frogs preyed on Orthoptera and Lepidoptera larvae, but juvenile frogs ate ants and spiders. As for food resources in the research site, the adult frogs showed selective preference for Lepidoptera larvae and less preference for Diptera larvae, ants and Ispoda, whereas the juvenile frogs showed preference for spiders and less preference for Diptera larvae, collembolans, and mites. These results indicate that the factors for choosing prey items were not only gape size of the frogs and the body size of prey items but also selectivity and evasiveness of the prey
