Does Vessel Noise Affect the Use of Sound by Foraging Orcinus orca (Killer Whales)?
Investigations on the behavioral responses of cetaceans to a variety of anthropogenic sounds are numerous, with a large proportion of these studies focused on responses to vessels (Nowacek et al. 2007; Richardson et al. 1995). Behavioral responses that affect activities associated with survival and reproduction are of particular concern because they have clearer repercussions on life functions. Furthermore, populations that are repeatedly exposed to vessels such as those that frequent urban ports and/or those targeted for vessel-based whale-watching activities also get particular attention given the consistency of the exposure (Clark et al. 2009; Jensen et al. 2009). Behavioral responses of killer whales to vessels include a decrease in foraging activity, an increase in dive duration and swim speed, and an increase in some surface-active behaviors (Lusseau et al. 2009; Noren et al. 2009; Williams et al. 2009). However, it remains unclear whether the physical presence and/or the sound emitted from motorized vessels is associated with the observed behavioral effects because information about received sound levels and other sound exposure variables were not reported in previous investigations.
We thank Anna-Maria Seibert, Christine Froschl, and Teresa Mongillo for field support. Val Veirs, Scott Veirs, and the students of Beamreach.org provided valuable support and assistance with hydrophone calibration, sound propagation, and localization error assessments.
Financial support was provided by the Northwest Fisheries Science Center, National Marine Fisheries Service (NMFS), National Oceanic and Atmospheric Administration (NOAA), Seattle, WA; the NOAA NMFS Ocean Acoustics Program, Silver Spring, MD; and the National Research Council Postdoctoral Associateship Program, Washington, DC.
We thank the conference organizers and sponsors for travel support to attend the Conference on the Effects of Noise on Aquatic Life in Cork, Ireland.
Data were collected under Scientific Research Permit No. 781-1824-00 from the US NMFS Office of Protected Resources, Silver Spring, MD, and Species at Risk Act/Marine Mammal Licence MML 2007-08/SARA-68 and MML 2008-05/SARA-85, Department of Fisheries and Oceans, Ottawa, ON, Canada.
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