Behavioral responses of acuminate horseshoe bats (Rhinolophus acuminatus) to sexually dimorphic echolocation calls
Sexual dimorphism in echolocation calls of bats is an unusual phenomenon because foraging and exploring the environment are believed to be the main forces shaping call frequency. However, recent studies also show that bats can acquire and express social information through echolocation calls. To date, thirteen bat species were reported to possess sexual dimorphism in call frequency, with either males or females emitting higher frequency, yet usually with overlapping frequency ranges. Potential reasons include population genetic structure, niche differentiation and mate choice.
In my Master thesis, I study a little-known species, the acuminate horseshoe bat Rhinolophus acuminatus, which is locally common in southeast Asia. Females have call frequencies that are 1-10 kHz higher than those of males without overlapping range. Since sexual dimorphism in echolocation call frequency is obvious in this species, I hypothesized that sexual selection plays a role in communication and social interactions in this bat. I predicted that males and females can discriminate between sexes, showing distinct differences in behavior and echolocation in response to playbacks of different sexes.
I recorded the natural echolocation behavior of a population of R. acuminatus in the natural roost in southern Thailand (Prince of Songkhla University, Hat-Yai). I conducted playback experiments, recording and filming their calls and behaviors in response to playbacks of natural calls and artificially frequency-shifted calls. Currently, I analyze the relationship between call frequency, sex and body size, and quantify the behaviors in the videos to investigate whether the bats react distinctively to different call frequencies and sexes.