Bohn KM, Boughman JW, Wilkinson G.S. & Moss CF (2004) Infant isolation call frequency matches hearing sensitivity in greater spear-nosed bats. J. Comparative Physiology A. 190: 185-192.
We investigated the relationship between auditory sensitivity and the vocal repertoire of greater spear-nosed bats (Phyllostomus hastatus). P. hastatus commonly emit three types of vocalizations. Adults emit group_specific foraging calls that range from 6 to 11 kHz and low amplitude echolocation calls that sweep from 80 to 40 kHz, while infants emit individually distinct calls that contain harmonics from 15 to 100 kHz. To determine if hearing in P. hastatus is differentially sensitive or selective to frequencies in these calls, we determined absolute thresholds and masked thresholds using an operant conditioning procedure. Both absolute and masked thresholds were lowest at 15 kHz, which corresponds with the peak energy of isolation calls. Auditory and masked thresholds were higher at sound frequencies used for group-specific foraging calls and echolocation calls. Isolation calls meet the requirements of individual signatures and facilitate parent-offspring recognition. Many bat species produce isolation calls with peak energy between 10 and 25 kHz, which corresponds to the frequency region of highest sensitivity in those species for which audiogram data are available. These findings suggest that selection for accurate offspring recognition exerts a strong influence on the sensory system of P. hastatus and likely on other species of group-living bats.