Gerstein, Laura

1 publication

Gerstein, Edmund R.; Gerstein, Laura; Forsythe, Steven E.; Blue, Joseph E. (detail)
1999The underwater audiogram of the West Indian manatee (Trichechus manatus).
Jour. Acoustical Soc. Amer. 105(6): 3575-3587. 2 tabs. 7 figs. June 1999.
—Behavioral experiments on two captive adult Florida manatees produced a U-shaped audiogram with auditory thresholds at 0.4 and 46 kHz and maximum sensitivity between 6 and 20 kHz. Detection thresholds of possible vibrotactile origin were measured at 0.015-0.2 kHz. Sensitivity falls 20 dB per octave below 0.8 kHz and approximately 40 dB per octave above 26 kHz. The audiogram demonstrates a wider range of hearing and greater sensitivity than was suggested by evoked-potential and anatomical studies. Inadequate sensitivity at low frequencies may contribute to manatees' inability to avoid collisions with motorboats. Use of high-frequency directional acoustic beacons on boats is suggested as a remedy.