Listening through the ears of echolocating Myotis daubentonii bats hunting in groups

Abstract

Echolocation allows bats to orient and catch insects in the dark. One intriguing question is how bats are able to recognize their own echoes when hunting in groups. Bats can adjust their call frequency, but this strategy may not be efficient for species like Myotis daubentonii emitting broadband frequency modulated signals. However, the actual masking may be reduced for bats like M. daubentonii emitting short directional signals with low duty cycle. We used a 12-microphone array and infrared camera to record flight and vocal behavior of groups of Daubenton’s bat hunting over a river in the field. We used flight path reconstructions to analyze the acoustic world from the bat’s perspective. For the focal bat, we reconstructed (1) its own emissions, (2) the pulses from conspecifics nearby, (3) its own insect echoes, and (4) insect echoes from pulses of the other bat. The data showed that when two bats fly together echoes were only rarely overlapped by the other sounds. We here provide a framework for obtaining detailed information of flight and echolocation behavior in complex natural surroundings, emphasizing the importance of adapting a “bat’s viewpoint” when studying natural echolocation.