Seasonal diets of two rhinolophid bats, Rhinolophus nippon and Rhinolophus cornutus, in the Southern Japanese Alps
Knowledge of diets is important for understanding species ecology and the mechanism of coexistence of multiple closely related species. Two rhinolophid bats, the greater Japanese horseshoe bat (Rhinolophus nippon) and the little Japanese horseshoe bat (Rhinolophus cornutus), occur in Japan, but little is known about their diets and interspecific interactions regarding food resources. In this study, we examined the fecal contents of these two species in the Southern Japanese Alps by microscopic analysis over multiple seasons. R. cornutus, which have more skillful flight, consumed nonvolant insects (caterpillars and spiders), whereas R. nippon did not; this indicates that R. cornutus can glean prey better than R. nippon. The larger-bodied R. nippon more frequently consumed hard-bodied beetles, whereas the smaller-bodied R. cornutus more frequently consumed soft-bodied dipterans and neuropterans. Body size differences influenced flight ability and bite force, which resulted in food resource partitioning and enabled multispecies coexistence of these closely related bats. A R. nippon nursery colony consumed a wider variety of insects, such as beetles, moths, and dipterans, during the pregnancy and lactation periods; however, after lactation, they showed a beetle-dependent diet, and before hibernation they again consumed various food resources. A R. cornutus non-nursery colony frequently consumed dipterans and moths in spring; dipterans, moths, and neuropterans in autumn; and moths and neuropterans in winter. These seasonal changes in diet seemed to be related to food supply or reproductive status.