Echolocating bats adjust sonar call features and head/ear position as they track moving targets in the presence of clutter

Echolocating bats often encounter clutter as they pursue insect prey. To probe the adaptive behaviors bats employ to mitigate the effects of clutter, this study quantified echolocation call features and head movements of big brown bats (Eptesicus fuscus) as they tracked a moving prey target in the dark. Bats were trained to rest on a perch and track an approaching target for a food reward. Clutter was positioned at different distances and angular offsets from the bat and the path of a moving target. This study hypothesized that bats dynamically adjust call features and head direction to facilitate target localization in the presence of clutter. The results show that bats shortened call duration and interval and increased head movements when the target was close to clutter. The study also revealed that bats increase the production of sonar strobe groups in cluttered environments, which may sharpen sonar spatial resolution. Spectral analysis showed that maximum call power shifted to lower frequencies when clutter was close to the target. These data demonstrate the big brown bat's range of adaptive behaviors that support target tracking in cluttered environments.