Blue whales are disturbed by military sonar

Blue whales are disturbed by military sonar

Military sonar has been found to disrupt the feeding behaviour of endangered blue whales.

Scientists found the giant sea mammals would cut short dives for food after a sonar 'ping' Photo: National News

By Richard Gray, Science Correspondent

6:00PM BST 03 Jul 2013

Researchers studied the responses of the biggest living animal on the planet to simulated mid-frequency military sonar, which is used by military submarines and ships to detect other vessels.

Using tracking tags on 17 blue whales, which feed on large swarms of krill in the ocean, the scientists found the giant sea mammals would cut short dives for food after a sonar “ping”.

The animals also tended to avoid areas where the sonar had been used for some time afterwards. The sonar was played at levels below the current regulatory thresholds.

The scientists claim this could mean the animals, which must eat large amounts of krill due to their body size, would miss out on vital time needed to forage for food.

They found that the whales stopped feeding for more than an hour after the sonar, resulting in a loss of around a metric ton of krill for the animals.

The researchers claim their findings contradict claims that military sonar has no impact on blue whales and other related species of baleen, or filter feeding, whales.

The findings are published in the journal Proceedings of the Royal Society B.

A second study by the same researchers, published in the journalBiology Letters, also showed that military sonar caused another species of whale, the Cuvier’s beaked whale, to stop feeding and swim away from the sound.

Dr Brandon Southall, from the Long Marine Laboratory at the University of California who led the project, said: “The two studies provide the first direct measurements of individual responses - for Cuvier's beaked whales and for any baleen whale species - to these kinds of mid-frequency sonar signals.

“These findings help us to understand risks to these animals from human sound and inform timely conservation and management decisions.”

The scientists argue that the impact of “active” military sonar on blue whales must be considered in environmental assessments before military naval exercises.

They said they hoped the US Navy, which funded the work, would use the findings to search for ways of reducing the impact of sonar on whale species.

Dr Stacy DeRuiter, from the University of St Andrews who also took part in the studies, said: "While there have been suspicions that military exercises are linked to whale strandings we don't really understand the chain of events that lead to that.

"The number of strandings also do not match the number of military exercises and sonar events, so the Navy is keen to understand this more."

http://www.telegraph.co.uk/earth/wildlife/10158068/Blue-whales-are-disturbed-by-military-sonar.html?fb