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Endangered Species Research

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ESR 21:143-160 (2013)  -  DOI:

Seismic operations have variable effects on dive-cycle behavior of bowhead whales in the Beaufort Sea

Frances C. Robertson1,2,*, William R. Koski2, Tannis A. Thomas2, W. John Richardson2, Bernd Würsig3, Andrew W. Trites

1Department of Zoology and Marine Mammal Research Unit, Fisheries Centre, University of British Columbia, Vancouver, British Columbia V6T 1Z4, Canada
2LGL Limited, environmental research associates, King City, Ontario L7B 1A6, Canada
3Department of Marine Biology, Texas A&M University at Galveston, Texas 77553, USA

ABSTRACT: The surfacing, respiration and diving (SRD) behavior of bowhead whales Balaena mysticetus changes upon exposure to seismic operations. However, it is unknown whether these changes differ by season, reproductive status (calves, mothers, and non-calves), and whale activity (traveling, foraging, or socializing). Such SRD behavioral responses to seismic operations might influence the detectability of whales during aerial surveys. We addressed these questions by applying non-parametric univariate tests and linear mixed models to behavioral data collected by aerial observation of bowheads in the Beaufort Sea from 1980 to 2000. Durations of surfacings decreased upon exposure to seismic operations, especially for traveling or socializing non-calf whales. The mixed models also indicated that dive durations were affected by the presence of seismic operations, but the effects depended on other variables such as season and whale activity. Overall, our results suggest that changes in the behavior exhibited by bowhead whales exposed to seismic operations are context-dependent (i.e. responses to seismic operations depend on both the circumstance and activity of the whale). The level of perceived threat may also be important based on similarities with behavioral changes observed in other air-breathing aquatic foragers facing dangers. We conclude that seismic-induced changes in bowhead SRD behaviors may affect the availability of bowhead whales for visual detection in some circumstances. This in turn means that estimates of abundance and distribution of bowhead whales near seismic surveys should be context-sensitive and incorporate correction factors that account for sound exposure, season, reproductive status, and whale activity.

KEY WORDS: Bowhead whale · Behavior · Disturbance · Seismic operations · Beaufort Sea · Aerial surveys · Sightability

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Cite this article as: Robertson FC, Koski WR, Thomas TA, Richardson WJ, Würsig B, Trites AW (2013) Seismic operations have variable effects on dive-cycle behavior of bowhead whales in the Beaufort Sea. Endang Species Res 21:143-160.

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