A behavioral audiogram for the fishing bat, Noctilio leporinus

Abstract

Behavioral audiograms were obtained from the fishing bat Noctilio leporinus which uses both constant frequency (CF) and frequency modulated (FM) pulses for echolocation. Three individuals were tested in a two choice operant conditioning procedure using tone bursts at various frequencies between 500 Hz and 120 kHz. Although there was some individual variation, the maximum auditory sensitivity (−1 to +5 dB SPL re 2.0 × 10−5 N/m2) was always within the range of the fundamental frequencies of the sonar pulse (32 to 58 kHz). Below this range, sensitivity declined at 30–40 dB/octave. Sensitivity below 10 kHz was very poor. There was a sharp reduction in sensitivity just above the CF component (56–58 kHz) of the sonar pulse and a plateau in the auditory sensitivity at frequencies corresponding to the second harmonic. N. leporinus thus lacks the sharply tuned auditory sensitivity characteristic of several other CF bats. However, its audiogram is in good agreement with the spectra of both its orientation pulses and communication sounds. [Supported by NSF grant BNS 79-05606.]