HEARING IN THE FM-BAT PHYLLOSTOMUS DISCOLOR - A BEHAVIORAL AUDIOGRAM

Absolute auditory thresholds of six adult lesser spear-nosed bats Phyl lostomus discolor (Chiroptera, Phyllostomidae) were determined in a tw o-alternative forced-choice procedure. Behavioral responses to pure to ne stimuli could be elicited throughout the tested frequency range of 5-142 kHz. The shape of the average audiogram is characterized by two sensitivity peaks and a pronounced increase of thresholds around 55 kH z, and towards the limits of the tested frequency range. The spectral extent of both sensitivity peaks shows a close relation to the bandwid th of two types of species-specific vocalizations. The first low thres hold area (> 10 and < 55 kHz) of the audiogram seems perfectly adapted to the directive call used for intra-specific communication, whereas the second sensitivity peak, centered around 85 kHz, covers most of th e bandwidth of the species' echolocation calls.