Asymmetric multi-frequency biosonar beam pattern of tongue-clicking bat, Rousettus aegyptiacus

The beam pattern of sonar signals emitted by echolocating animals, such as bats and toothed whales, directly influences the acoustic information available for guiding task-specific behaviors. The lingual echolocating bat, Rousettus aegyptiacus, emits broadband transient sonar clicks that resemble those of dolphins. The clicks are emitted in left-right pairs, with the maximum intensity slope of each signal pointing toward the target during navigation. However, detailed beam pattern characteristics of these lingual sonar clicks remain unknown. Using a loosely populated three-dimensional microphone array, we systematically characterize the multi-frequency beam structure of R. aegyptiacus in the entire azimuth-elevation domain. The bat’s head aim was recorded by an infrared high-speed motion-capture camera system. We show that the sonar beam of R. aegyptiacus tongue clicks is vertically elongated and exhibits an unusual multi-frequency structure that has not been described previously in the literature. Specif...