Foraging niche partitioning of three Myotis bat species and marine fish consumption by Myotis pilosus in a subtropical East Asian region
Most bats are insectivorous, but some species have evolved the ability to prey on fish. Although piscivory has been confirmed in the Ricketts big-footed myotis (Myotis pilosus), the extent of piscivory of other cohabiting Myotis species is uncertain. This study aims to explore the dietary niches and fish consumption of three Myotis species in a subtropical East Asian region, and specifically the fish diet of M. pilosus. Our findings reveal, for the first time, that M. pilosus consumes marine fishes, in contrast to previous research conducted in inland regions that suggested year-round consumption of cyprinids in freshwater habitats. We also observed seasonal variation in the diets of M. pilosus. It predominately hunted wide-banded hardyhead silverside, sailfin flying fish, and shorthead anchovy during the wet season, while mainly preying upon mullets during the dry months. In more inland areas, M. pilosus was found to primarily feed on invasive freshwater poeciliids. Furthermore, M. pilosus consumed more fish during the dry season, while there was a greater consumption of insects during the wet months. Most notably among our findings is the consumption of fish by two individuals of Horsfields myotis (M. horsfieldii), indicating that the species is potentially piscivorous. We revealed that both M. horsfieldii and M. pilosus consumed water striders, suggesting that foraging of aquatic insects could be driving the evolution of fishing behavior. Our findings have also shed light on the flexibility of foraging behavior in piscivorous bats.