Accurate sound localization behavior in a gleaning bat, Antrozous pallidus

Acute auditory processing in bats is typically associated with echolocation. A subset of bats, called gleaners, listens to prey-generated noise to hunt surface-dwelling prey. Gleaners depend less on echolocation to hunt and, therefore, accurate localization of prey-generated noise is necessary for foraging success. Here we studied azimuth sound localization behavior in the pallid bat, a gleaning bat in which spatial encoding has been studied extensively. We tested pallid bats on a relatively difficult open loop task (single sound, duration ≤ 200 ms). The bats were trained to face the midline when stimulus was presented, and this was confirmed with video analysis. Bats localized broadband noise (5-30 kHz) from 1 out of 11 speakers spaced evenly across the horizontal plane of the frontal sound field. Approach to the correct speaker was rewarded. Pallid bats show accurate localization near the midline with mean errors between 3-6°. Remarkably, the accuracy does not decline significantly at peripheral locations with bats averaging  <~7° error upto 72° off midline. Manipulation of stimulus bandwidth shows that higher frequencies (20-30 kHz) are necessary for accurate localization. Comparative studies of gleaning bats will reveal convergent adaptations across auditory systems for non-echolocation-based behaviors in bats.