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Oceans: Study assesses sonar impacts to blue whales

Biologists find nuanced response to simulated noise pollution

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Some blue whales abandon feeding areas when exposed to sonar-like noise pollution, scientists found after tagging some of the cetaceans in the California Bight. Photo courtesy NOAA.

By Summit Voice

FRISCO — Biologists are a little closer to understanding how the use of sonar during naval training exercises affects blue whales, with a new study showing that some tagged whales feeding in deep water stopped eating and sped up or moved away from sonar-like noise

The study, funded by the U.S. Navy, showed that the response to noise pollution is nuanced, depending in part on the what the whales are doing at the time. To assess the impacts, the researchers tagged whales and simulated mid-frequency sonar sounds significantly less intense than the military uses.

“Whales clearly respond in some conditions by modifying diving behavior and temporarily avoiding areas where sounds were produced,” said lead author Jeremy Goldbogen of Cascadia Research. “But overall the responses are complex and depend on a number of interacting factors,” he said.

The scientists tagged the whales with non-invasive suction cups, which recorded acoustic data and high-resolution movements as the animals were exposed to the controlled sounds.

“The tag technology we use offers a unique glimpse into the underwater behavior of whales that otherwise would not be possible,” said Ari Friedlaender, a research scientist at the Duke Marine Laboratory.

“Blue whales are the largest animals that have ever lived. Populations globally remain at a fraction of their former numbers prior to whaling, and they appear regularly off the southern California coast, where they feed,” said John Calambokidis, one of the project’s lead investigators of Cascadia Research.

That area of the ocean is also the site of military training and testing exercises that involve loud mid-frequency sonar signals. Such sonar exercises have been associated with several unusual strandings of other marine mammal species (typically beaked whales) in the past. Until this study, almost no information was available about whether and how blue whales respond to sonar.

“These are the first direct measurements of individual responses for any baleen whale species to these kinds of mid-frequency sonar signals,” said Brandon Southall, SOCAL-BRS chief scientist from SEA, Inc., and an adjunct researcher at both Duke and the University of California Santa Cruz. “These findings help us understand risks to these animals from human sound and inform timely conservation and management decisions.”

A related paper published July 3 by the same research team in Biology Letters has shown clear and even stronger responses of Cuvier’€™s beaked whales to simulated mid-frequency sonar exposures. Beaked whales showed a variety of responses to both real, military sonar in the distance and nearby simulated sonar. What the beaked whales were doing at the time appeared to be a key factor affecting their reactions.

 

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