Feeding Relationships between Hyla japonica and Rana nigromaculata in Rice Fields of Japan

Abstract

We examined feeding relationships between Hyla japonica and Rana nigromaculata in rice fields of central Japan, where they forage syntopically. Hyla japonica and recently metamorphosed Rana nigromaculata overlapped greatly in body size and took prey of similar size and type. However, H. japonica foraged in rice fields during its breeding season (May to July), whereas R. nigromaculata began metamorphosis later in July. Therefore, they seldom coexisted and seemed to partition food resources temporally. By the following spring, R. nigromaculata froglets grew larger than adult H. japonica and used different food resources, suggesting food resources were partitioned by body size. These patterns of food partitioning, which were consistent in two study sites where the dominant species differed, may account for coexistence of H. japonica and R. nigromaculta throughout their wide distributions.