Estimation of auditory response thresholds in humpback whales using biologically meaningful sounds
- Adam S. Frankel, Joseph R. Mobley, Jr. and Louis M. Herman
(C) 1995 De Spil Publishers
Conventional methods for determining auditory detection thresholds in cetaceans have been limited to psychophysical or evoked potential techniques using captive odontocetes. Sound playback techniques offer a means to assay response thresholds in free-ranging cetaceans, including mysticetes. Thus far, the use of sound playback to determine response thresholds has been limited primarily to transmission of anthropogenic noise. In contrast, playback of conspecific vocalizations offers a mechanism to estimate thresholds of response to biologically meaningful sound.
Humpback whales were exposed to playbacks of three conspecific vocalizations (song, social sounds, and feeding call), synthetic sounds and a blank tape control. Whales were observed and tracked from shore. The strongest reaction to playback was a rapid approach response, which was initiated at ranges as great as 2.8 km from the sound source. Empirical transmission loss measurements were compared with the Marsh and Schulkin semi-empirical model. A logarithmic curve fitted to empirical data was used to estimate the received levels for animals at known ranges from the sound source. Whales responded at an estimated received broadband level as low as 102 dB re 1 mPa for the feeding call, and 106 dB re 1 mPa for synthetic sound. These estimates of response threshold are potentially biased upwards, because animals may detect a sound without any discernible response. However, this technique may be the only feasible method for behaviorally estimating auditory detection thresholds in free-ranging cetaceans, especially mysticetes.
Frankel, A. S., Mobley, J. R., & Herman, L. M. (1995). Estimation of auditory response thresholds in humpback whales using biologically meaningful sounds. In R. A. Kastelein, J. A. Thomas, & P. E. Nachtigall (Eds.), Sensory systems of aquatic animals., 55-70. Woerden, The Netherlands: De Spil Publishers. Back to Top Dolphin Programs | Whale Programs | Education Programs | Our Research | Resource Guide Copyright © 2002, The Dolphin Institute |
