Coexistence of two sympatric and morphologically similar bat species Rhinolophus affinis and Rhinolophus pearsoni

Ecologists have long focused on the coexistence of sympatric species. Here, we investigated two horseshoe bat species, Rhinolophus affinis and Rhinolophus pearsoni inhabited in the same cave, for their foraging strategies, niche differentiation, prey selection, and their coexistence status. These two species of horseshoe bats were different in the dominant frequency of their echolocation calls, but similar in their morphology. We found evidence for prey selectivity although there was a high degree of overlap in prey categories and sizes. R. affinis and R. pearsoni foraged on 16 and 7 categories insects, respectively, with Pyralidae, Geometridae, Melolonthidae dominating their diets. The degree of trophic niche overlap was 0.69. Pairwise comparisons suggested that there was no obvious differentiation in prey categories and size. However, high prey availability in the environment (Simpson diversity index = 0.79 and Margalef richness index = 4.12) contributed to their coexistence by dampening the interspecific competition. Since there are one or more mechanisms facilitating species coexistence in a community, our results suggest that the spatial niche differentiation in foraging microhabitats and in foraging habitats at landscape scale may promote the coexistence of the two bat species. However, additional field data are needed to confirm this speculation.