title: Dose-response relationships for the onset of avoidance of sonar by free-ranging killer whales.
abstract: Eight experimentally controlled exposures to 1-2 kHz or 6-7 kHz sonar signals were conducted with four killer whale groups. The source level and proximity of the source were increased during each exposure in order to reveal response thresholds. Detailed inspection of movements during each exposure session revealed sustained changes in speed and travel direction judged to be avoidance responses during six of eight sessions. Following methods developed for Phase-I clinical trials in human medicine, response thresholds ranging from 94 to 164 dB re 1 μPa received sound pressure level (SPL) were fitted to Bayesian dose-response functions. Thresholds did not consistently differ by sonar frequency or whether a group had previously been exposed, with a mean SPL response threshold of 142 ± 15 dB (mean ± s.d.). High levels of between- and within-individual variability were identified, indicating that thresholds depended upon other undefined contextual variables. The dose-response functions indicate that some killer whales started to avoid sonar at received SPL below thresholds assumed by the U.S. Navy. The predicted extent of habitat over which avoidance reactions occur depends upon whether whales responded to proximity or received SPL of the sonar or both, but was large enough to raise concerns about biological consequences to the whales.
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Patrick J O
authors.initials: PJ
authors.lastname: Miller
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Ricardo N
authors.initials: RN
authors.lastname: Antunes
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Paul J
authors.initials: PJ
authors.lastname: Wensveen
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Filipa I P
authors.initials: FI
authors.lastname: Samarra
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Ana Catarina
authors.initials: AC
authors.lastname: Alves
authors.affiliation: Sea Mammal Research Unit, Scottish Oceans Institute, University of St Andrews, St Andrews, Fife KY16 8LB, Scotland.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Tyack
authors.affiliation: Maritime Systems Division, Norwegian Defence Research Establishment (FFI), NO-3191 Horten, Norway.
authors.forename: Petter H
authors.initials: PH
authors.lastname: Kvadsheim
authors.affiliation: Maritime Systems Division, Norwegian Defence Research Establishment (FFI), NO-3191 Horten, Norway.
authors.forename: Lars
authors.initials: L
authors.lastname: Kleivane
authors.affiliation: Acoustics and Sonar, Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 96864 The Hague, 2509 JG, The Netherlands.
authors.forename: Frans-Peter A
authors.initials: FP
authors.lastname: Lam
authors.affiliation: Acoustics and Sonar, Netherlands Organisation for Applied Scientific Research (TNO), P.O. Box 96864 The Hague, 2509 JG, The Netherlands.
authors.forename: Michael A
authors.initials: MA
authors.lastname: Ainslie
authors.affiliation: Centre for Research into Ecological and Environmental Modelling, University of St Andrews, Fife KY16 9QQ, Scotland.
authors.forename: Len
authors.initials: L
authors.lastname: Thomas
mesh_terms: D000161:Acoustic Stimulation; D000818:Animals; D001307:Auditory Perception; D001309:Auditory Threshold; D001362:Avoidance Learning; D001499:Bayes Theorem; D001522:Behavior, Animal; D003198:Computer Simulation; D017753:Ecosystem; D009038:Motion; D009792:Oceans and Seas; D011312:Pressure; D013016:Sound; D013550:Swimming; D013997:Time Factors; D014465:Ultrasonics / Q000379:methods*; D050685:Whale, Killer / Q000502:physiology / Q000523:psychology*