Male sperm whale behaviour during exposures to distant seismic survey pulses

Abstract

The behaviour of adult, male sperm whales in polar waters (69$ 20% N, 15$ 40% E) during exposure to pulses from ar emote (>2 0k m) seismic survey vessel and artificial codas is described and discussed. Five hours of recordings with al arge aperture array contained both air gun pulses and sperm whale clicks. The seismic survey pulses received were smeared-out in time and high-pass filtered due to multipath propagation in shallow water. The pulses received had a 10 dB spectrum content in the frequency range of 210‐260 Hz and am aximum 10 dB duration of 1400 ms. Estimated maximum sound pressure received at the whales were 146 dB re 1 Pa (p-p) (124 dB re 1 Pa 2 si ne nergy terms). The exposure to the seismic survey pulses did not elicit observable avoidance and the whales stayed in the area for at least 13 days of exposure. Nor did the whales fall silent or change their normal vocal patterns during feeding dives. It appears that foraging male sperm whales in this habitat and at these received levels are not more susceptible to air gun pulses than are cetaceans in general. During emissions of artificial codas, sound levels at the whales being unknown, the sperm whales did not cease clicking as reported from previous investigations, but two whales seemed to direct their high power, narrow-beam sonar towards the coda transmitter.