Kerwin J. Finley
LGL Ltd., Environmental Res. Associates, P.O. Box 280, King City, ON L0G 1K0, Canada
Charles R. Greene
Greeneridge Sci., Inc., Santa Barbara, CA 93110
Responses of belugas and narwhals to ice-breaking ships were studied during three spring seasons. The two species reacted differently. Belugas exhibited panic as ships approached at distances of 35--50 km; received noise levels ranged from 94--105 dB re: 1 (mu)Pa (20- to 1000-Hz band). Sound spectrographs revealed a tone at 105 Hz from an ore-carrier ship at 130 km. Presumed alarm calls indicated that belugas were aware of the ore carrier at 85 km (101 dB, 20- to 1000-Hz band level); they moved up to 80 km away from ice-breaking operations. In contrast, narwhals showed subtle ``freeze'' responses and dispersed slowly. Ship approaches caused narwhals to cease vocalizing temporarily whereas belugas emitted noisy alarm calls. Narwhals returned to disturbance areas faster than belugas and resumed normal activities when received noise levels from ice-breaking operations were as high as 120 dB. These responses occurred at unprecedented ranges, but no previous field studies had been conducted in areas with marine mammal populations unaccustomed to industrial noises. The disparity between field observations and theory, based on beluga audiograms, is examined. Results of Finley et al. [Can. Bull. Fish. Aqua. Sci. 224 (1990)] are augmented by additional acoustical analyses. [Work supported by Canadian Dept. of Indian Affairs & Northern Development.] [sup a)]Present address: 10232 Summerset Place, Sidney V8L 4X2, Canada.