Cochlear resonance in the mustached bat: Behavioral adaptations

Abstract Mustached bats. Pteronotus p. parnellii . use complex, multiharmonic biosonar signals with prominent approx. 60 kHz (CF) components. The sense of hearing is especially acute to sounds near 60 kHz and the cochlea shows a number of specializations in the 60 kHz region. Foremost is a remarkable degree of cochlear resonance. In this study it is shown that: 1) any sounds near the resonance frequency elicit a pronounced resonance that continues after the stimulus terminates; 2) Doppler-shifted echoes of the bat's own cries may cause resonance; 3) continuous resonance can be produced by stimulating the ear with broadband noise but such resonance does not interfere with the bat's ability to Doppler-shift compensate during simulated flight; 4) significant changes in the resonance frequency of the cochlea occur during and after flight; 5) the changes in resonance can be dependent or independent of body temperature changes; and 6) mustached bats continuously adjust the CF component of their pulses to keep the second harmonic echoes in a constant frequency band near the resonance frequency. Thus, mustached bats not only compensate for Doppler-shifts imposed by their movements relative to that of a target, but they cochlear resonance compensate to deal with small changes in the micromechanical properties of the cochlea.