Acoustic responses of Baleen whales to low-frequency, man-made sounds

Abstract

In the last 5 years, two projects were undertaken to evaluate impacts of man-made sounds on whales. Baleen whales were identified as ‘‘at risk’’ because of their use of low-frequency sound for communication, their endangered status, and studies showing responses to continuous noises at exposure levels >120 dB, re: 1 μPa. To evaluate the potential impact of operational ATOC (195-dB source intensity), humpback whales off Kauai were studied during the breeding season. To evaluate the potential impact of U.S. Navy SURTASS LFA sonar, playback experiments were conducted on four species at exposures of 120–155 dB. LFA research was designed to obtain responses during feeding (blue and fin whales, southern California, September–October), migration (gray whales, central California, January) and breeding (humpbacks, Hawaii, March). For the ATOC source, humpbacks showed statistically significant but subtle responses over small time and spatial scales. There were no changes in singing, or larger-scale changes in distribution or relative numbers. For LFA experiments off southern California, whales did not change vocal rates or leave the testing area, and there were no immediately observable responses, even at exposure levels up to 150 dB. Tyack (this session) will discuss results from the gray and humpback whale LFA experiments.