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
|
