Christopher W. Clark
Bioacoust. Res. Program, Cornell Lab. of Ornithol., 159 Sapsucker Woods Rd., Ithaca, NY 14850
William T. Ellison
Marine Acoustics, Inc.
One reason for concern over potential effects of man-made sounds on marine mammals stems from the fact that most baleen whales produce intense, low-frequency sounds. Complete descriptions of vocal repertoires are still lacking for many of the 11 species, and our understanding of how whales use sounds is poor. The application of passive array techniques has provided unique and exciting insights into the biological significance of whale sounds. Acoustic studies on bowhead whales migrating off Point Barrow, Alaska and recent work on pelagic species (including blue, finback, and minke whales) clearly demonstrate that whales are vocally active and produce a variety of signals. Whales counter-call, adopt distinctive call types when traveling in acoustic herds, sing complex songs using two simultaneous, nonharmonically related voices, and produce extremely long, patterned sequences of infrasonic calls. These results support the conclusion that sounds serve a variety of important communicative functions. There is also reason to believe that some whales actively use surface reverberation as a navigational cue. Thus the concern over the potential impact of man-made noise on the whales' acoustic behaviors is legitimate and this issue requires continued attention. [Work supported by ARPA, ONR, and the Department of Wildlife Management, Barrow, AK.]