Naval Sonar Exercises Linked to Whale Strandings

http://www.sciencedaily.com/releases/2011/03/110316153133.htm

ScienceDaily (Mar. 16, 2011) — Scientists have long been aware of a link between naval sonar exercises and unusual mass strandings of beaked whales. Evidence of such a link triggered a series of lawsuits in which environmental groups sued the U.S. Navy to limit sonar exercises to reduce risk to whales. In 2008, this conflict rose to the level of the US Supreme Court which had to balance potential threat to whales from sonar against the military risk posed by naval forces inadequately trained to use sonar to detect enemy submarines. The court ruled that the Navy could continue training, but that it was essential for the Navy to develop better methods to protect the whales.

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Now, an international team of researchers reports in a paper led by Tyack the first data on how beaked whales respond to naval sonar exercises. Their results suggest that sonar indeed affects the behavior and movement of whales.

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"This suggests that beaked whales are particularly sensitive to sound. Their behavior tended to be disrupted at exposure levels around 140 decibels (dB), so they may require a lower threshold than many current regulations that anticipate disruption of behavior around 160 dB, " said Tyack. "But the observations on the naval range suggest that while sonar can disrupt the behavior of the whales, appropriate monitoring and management can reduce the risk of stranding."

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