Target discrimination by the echolocating bat Vampyrum spectrum

Five specimens of Vampyrum spectrum were trained to discriminate between solid targets differing in shape or size using echolocation alone. A pair of lucite targets, one a sphere, the other a prolate spheroid, were then designed so as to produce echoes of approximately equal overall amplitude at the distance of choice by the bats, but of different frequency composition. This discrimination was successfully performed by four of the animals and the two best performers were studied in detail by photographic analysis to ascertain whether frequency or amplitude cues were actually being utilized. By manipulating the degree of frequency dependence in the echoes, it was shown that one animal seemed to rely on the availability of frequency‐dependent cues for successful discrimination while the other did not. Examination of the structure of the pulses used on these flights indicated a consistent pattern of changes as the targets were approached. Some of these changes could be correlated with the kinds of cues the two bats seemed to be using in making the discriminations.