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High thresholds for avoidance of sonar by free-ranging long-finned pilot whales (Globicephala melas)

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Author: Antunes, R. · Kvadsheim, P.H. · Lam, F.P.A. · Tyack, P.L. · Thomas, L. · Wensveen, P.J. · Miller, P.J.O.
Type:article
Date:2014
Source:Marine Pollution Bulletin, 1, 83, 165-180
Identifier: 507081
doi: doi:10.1016/j.marpolbul.2014.03.056
Keywords: Marine · Dose-response · Marine mammals · Noise · Pilot-whales · Sonar · Environmental impact · Avoidance response · Behavioral response · Dose response · Sonar · Whales · Animal behavior · Controlled study · Killer whales · Long finned pilot whale · Navy · Prediction · Threshold · Defence Research · Defence, Safety and Security · Physics & Electronics · AS - Acoustics & Sonar · TS - Technical Sciences

Abstract

The potential effects of exposing marine mammals to military sonar is a current concern. Dose-response relationships are useful for predicting potential environmental impacts of specific operations. To reveal behavioral response thresholds of exposure to sonar, we conducted 18 exposure/control approaches to 6 long-finned pilot whales. Source level and proximity of sonar transmitting one of two frequency bands (1-2kHz and 6-7kHz) were increased during exposure sessions. The 2-dimensional movement tracks were analyzed using a changepoint method to identify the avoidance response thresholds which were used to estimate dose-response relationships. No support for an effect of sonar frequency or previous exposures on the probability of response was found. Estimated response thresholds at which 50% of population show avoidance (SPLmax=170dB re 1μPa, SELcum=173dB re 1μPa2s) were higher than previously found for other cetaceans. The US Navy currently uses a generic dose-response relationship to predict the responses of cetaceans to naval active sonar, which has been found to underestimate behavioural impacts on killer whales and beaked whales. The navy curve appears to match more closely our results with long-finned pilot whales, though it might underestimate the probability of avoidance for pilot-whales at long distances from sonar sources. © 2014 Elsevier Ltd.