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Beaked whale controlled exposure study

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Initial Cruise Report From First Controlled Exposure Studies of Beaked WhalesIan Boyd, Diane Claridge, Christopher Clark, Brandon Southall, Peter Tyack. Behavioral Response Study-2007, Cruise Report, Phase 1    A summary of the project, and the preliminary cruise report are available: [WEBSITE]During August and September, 2007, the first controlled exposure experiments aimed at learning more about the ways that beaked and pilot whales respond to exposure to mid-frequency active sonar took place in the Bahamas. For the past decade or more, much emphasis has been placed on discovering what sound levels cause TTS (temporary threshold shifts, or short-term hearing impairment), with the thought that these levels could serve as a benchmark of exposure levels that we should be concerned about; however, it appears that in some cases, beaked whales that ended up stranding were exposed to much lower sound levels. Hence, the need to learn more about how they change their dive patterns and other behaviors in response to moderate sound exposure. D-tags, which have been successfully used in studies of sperm whales for several years, provide an opportunity to safely measure received sound levels and dive patterns simultaneously. The tags are applied with a long pole when the whales are at the surface, remain attached via suction cups, and fall off within 10 or 15 hours. The researchers noted that, in the absence of a clear sense of when and why some beaked whales are affected to such a strong degree that they beach and die, the result has been a highly precautionary and sometimes arbitrary approaches to management of sound, leading to debates between interested parties that have at times been difficult and ultimately unproductive. In planning for these experiments, the researchers worked with a wide range of parties, including environmental NGOs; while some NGOs had strong reservations about controlled exposure studies, the researchers note that “a constructive spirit of dialogue contributed to the success of the study.” Goals of this study: to establish protocols for tagging and careful controlled exposures, to discern exposure parameters that cause a behavioral response (change in behavior), and to compare any responses to sonar signals and orca sounds, to begin to explore whether they respond to sonar as a possible predator. Ten animals were successfully tagged; 6 Blainsvilles beaked whales and 4 pilot whales. Seven provided control/baseline measurements, and 3 tagged animals were exposed to playbacks of MFA and/or orca sounds (1 beaked, 2 pilot). The researchers provide rather detailed descriptions of the responses of the one beaked whale that was tagged during controlled exposure; of course, with only one sample, and few controls, all results are very tentative.

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