Reconstruction of flight and acoustic behavior of echolocating bats

A method for localizing sounds was applied to simultaneously reconstruct the emission pattern and flight path of echolocating bats. An infrared camera and an array of three microphones were used to record simultaneous audio signals and video images of groups of bats while foraging. The bats studied (Eptesicus, Myotis, Pipistrellus) use frequency sweeping ‘‘chirps’’ in the 25–45 kHz to 100–120 kHz band for echolocation. Cross correlation of the bats’ chirps was used to find delays in chirp arrival time between microphones in the array. These delays were then used to locate the chirps’ direction. A time-series of these coordinates was found, then calibrated to pixel points of the corresponding infared video recording to reconstruct the flight path and chirp pattern for each of the bats over 15-s intervals. By providing simultaneous emission and position information throughout time, this method addresses questions about dynamic adaptation of the emission patterns of bats to the acoustic environment. Simultaneous adaptation between bats flying in groups is particularly interesting. An accompanying abstract discusses the implications of these findings for the current paradigm of information processing in the FM bat’s auditory pathway.