Foraging among acoustic clutter and competition: Vocal behavior of paired big brown bats

Abstract

In their natural environment, big brown bats forage for small insects in open spaces, as well as in the presence of acoustic clutter. While searching and hunting for prey, these bats experience sonar interference not only from densely cluttered environments, but also through calls from other conspecifics foraging close-by. Previous work has shown that when two bats fly in a relatively open environment, one of them may go silent for extended periods of time (Chiu et al. 2008), which may serve to minimize such sonar interference between conspecifics. Additionally, big brown bats have been shown to adjust frequency characteristics of their vocalizations to avoid acoustic interference from conspecifics (Chiu et al., 2009). It remains an open question, however, in what way environmental clutter and the presence of conspecifics influence the bat’s call behavior. By recording multichannel audio and video data of bats engaged in insect capture in an open and a cluttered space, we quantified the bats’ vocal behavior. Bats were flown individually and in pairs in an open and cluttered room, and the results of this study shed light on the strategies animals employ to negotiate a complex and dynamic environment.