Texture discrimination by echolocation in the big brown bat.

Abstract

Echolocating bats emit high-frequency vocalizations and listen to the returning echoes to sense their environment. Echolocation transforms the physical environment into acoustic energy which bats use for navigation and prey capture. This study examined the capabilities of the big brown bat, Eptesicus fuscus, to identify and discriminate textured objects. The bat was trained to discriminate a smooth object from a textured object, both spherical, ∼ 15 mm diameter, and tethered to the ceiling in a large flight room. The bat was free to fly and investigate the objects before making its decision (signaled by tapping one of the objects in flight − correct=smooth). The bat’s discrimination performance was measured with a series of textured objects. Quantification of texture was made through acoustic recordings of the objects. High-speed video recordings allowed a reconstruction of the bat’s three-dimensional flight path, full bandwidth ultrasound-sensitive microphones allowed recordings of the bat’s sonar emissions, and an array of microphones positioned around the flight room allowed a reconstruction of the bat’s sonar beam pattern. The relationship between the bat’s performance and the acoustic recordings of the stimuli was examined. How the bat’s motor behaviors contribute to its discrimination performance was investigated. [Work supported by NSF(REU), NIMH(R01MH056366.]