Hearing in American leaf-nosed bats. I: Phyllostomus hastatus

We determined the audiogram of Phyllostomus hastatus (the greater spear-nosed bat), a large, omnivorous American leaf-nosed bat native to Central and South America. A conditioned suppression/avoidance procedure with a fruit juice reward was used for testing. At an intensity of 60 dB sound pressure level (SPL re 20 microN/m(2)), the hearing range of P. hastatus extends from 1.8 to 105 kHz, with a best sensitivity of 1 dB SPL at 20 kHz. Both its high-frequency and low-frequency hearing are not unusual for a small mammal. Despite its use of low-intensity echolocation calls there was no evidence for unusual sensitivity to either the frequencies used for echolocation or to the main frequencies of its communication calls, suggesting no selective "tuning" of the audiogram. Its behavioral pure-tone thresholds are lower than the multi-unit thresholds in the inferior colliculus.