ABSTRACT
Echolocating bats have evolved a remarkable biological sonar system which they use to orient in the environment and capture insect prey. The bat produces ultrasonic vocalizations and listens to echoes that reflect off targets in the path of the sound beam. From the features of echoes, the bat gathers information about a target’s size, range, and velocity of movement. This chapter reviezos research over the last thirty years on target ranging in bats, and details a series of recent behavioral experiments with the FM-bat, Eptesicus fuscus that examine the bat’s perception along the range axis. Psychophysical data demonstrate that bats estimate target distance from the time delay betzueen sonar emissions and returning echoes, and that FM-bats can discriminate changes in echo delay of less than 0.5 ms, corresponding to changes in distance of less than a millimeter. When the bat encounters multiple echoes from closely-spaced reflecting surfaces, the bat uses the echo delay from the nearest surface to estimate the absolute target distance and uses the composite echo spectrum to determine the range profile of the complex target. The range profile of a target is initially encoded in the spectral interference pattern of overlapping echoes; hozoever, it is ultimately represented along the same perceptual dimension the bat uses for estimating the absolute distance to a target.
