July 3, 2013 — Some blue whales off the coast of California change their behavior when exposed to the sort of underwater sounds used during U.S. military exercises. The whales may alter diving behavior or temporarily avoid important feeding areas, according to new research.
The Southern California Behavioral Response Study exposed tagged blue whales in the California Bight to simulated mid-frequency (3.5-4 kHz) 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,” including whether the whales were feeding deep, shallow or not at all.
The study, funded by the U.S. Navy Chief of Naval Operations Environmental Readiness Division and the U.S. Office of Naval Research, appears July 3 in the Proceedings of the Royal Society B.
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.a
The scientists found that some of the whales engaged in deep feeding stopped eating and either sped up or moved away from the source of the noise. Not all of the whales responded to the noise, and not all in the same way.
“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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The above story is reprinted from materials provided by Duke University.
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Journal Reference:
- J. A. Goldbogen, B. L. Southall, S. L. DeRuiter, J. Calambokidis, A. S. Friedlaender, E. L. Hazen, E. A. Falcone, G. S. Schorr, A. Douglas, D. J. Moretti, C. Kyburg, M. F. McKenna, P. L. Tyack. Blue whales respond to simulated mid-frequency military sonar. Proceedings of the Royal Society B: Biological Sciences, 2013; 280 (1765): 20130657 DOI: 10.1098/rspb.2013.0657
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Whales flee from military sonar leading to mass strandings, research shows
Studies are missing link in puzzle that has connected naval exercises to unusual mass strandings of whales and dolphins
- The Guardian, Tuesday 2 July 2013
Whales flee from the loud military sonar used by navies to hunt submarines, new research has proven for the first time. The studies provide a missing link in the puzzle that has connected naval exercises around the world to unusual mass strandings of whales and dolphins.
Beaked whales, the most common casualty of the strandings, were shown to be highly sensitive to sonar. But the research also revealed unexpectedly that blue whales, the largest animals on Earth and whose population has plummeted by 95% in the last century, also abandoned feeding and swam rapidly away from sonar noise.
The strong response observed in the beaked whales occurred at noise levels well below those allowed for US navy exercises. “This result has to be taken into consideration by regulators and those planning naval exercises,” said Stacy DeRuiter, at the University of St Andrews in Scotland, who led one of the teams.
“For whales and dolphins, listening is as important as seeing is for humans – they communicate, locate food, and navigate using sound,” said Sarah Dolman, at charity Whale and Dolphin Conservation. “Noise pollution threatens vulnerable populations, driving them away from areas important to their survival, and at worst injuring or even causing the deaths of some whales and dolphins.” Dolman said there were no accepted international standards regarding noise pollution and there was an urgent need to re-evaluate the environmental impacts of military activities.
The US Navy part-funded the new studies but said the findings only showed behavioural responses to sonar, not actual harm. Nonetheless, Kenneth Hess, a US Navy spokesman, said permit conditions for naval exercises were reviewed annually and added: “We will evaluate the effectiveness of our marine mammal protective measures in light of new research findings.”
Unusual mass strandings, where multiple species of whale and dolphin beach at several locations at once, have soared since the introduction of military sonar in the 1950s and can be fatal. The strandings occur every year and major recent events saw up to 15 animals beached in the Canary Islands, the Bahamas and Greece. In May, the naval activity was found to be the most probable cause of the deaths of at least 26 short-beaked common dolphins in Falmouth Bay, Cornwall in June 2008.
Beaked whales are the most common species affected by unusual mass strandings, perhaps because their shy nature makes them more easily scared by noises that they may interpret as killer whale sounds. Researchers used suction cups to attach digital devices to Cuvier’s beaked whales off the coast of Southern California to measure the noise they were exposed to and their response.
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