California Study Finds Military Sonar Forcing Whales to Get DCS

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A Cuvier's beaked whale diving

Military sonar is so loud that whales are getting bent to avoid the noise. A study of beaked whales off California reveals that the whales, when faced with sonar, are diving far longer and to greater depths and being forced to take longer surface intervals disrupting their food gathering.

Researchers at the Marine ecology Telemetry Research Centre in Seabeck, Washington state, attached satellite tags to 16 Cuvier's beaked whales in a military testing zone about 150 miles southwest of Los Angeles.

One of the whales dived for a record-breaking two hours and 17 minutes, to a depth of two miles. The study confirmed that in the presence of sonar the whiles dived for longer and were forced to take longer surface interval breaks from diving. Without sonar active in the area, they would dive eight times a day, but only two or three times when the area was being sonar surveyed. 

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Pilot whales are one of the many species of whales recently found beached with nitrogen bubbles embedded in their fat

The military broadcast sonar waves louder than the noise made at rock concerts but just above the range of human hearing to locate submarines. Sonar from helicopters was found to be particularly disruptive.

The report in Royal Society Open Science said the whales were risking decompression sickness making such long dives to great depths.

It has long been theorised that sonar plays a role in the increasing number of whales being found stranded on beaches and autopsies have found their fat riddled with nitrogen bubbles. This study confirms that sonar is forcing whales to make longer dives.

In the 1990s a mass stranding of Cuvier's beaked whales was linked to a NATO exercise in the Mediterranean near Greece. Since then the US Navy has checked whether any beaked whales are in the area before such military exercises take place. However, European forces don't and such exercises regularly take place in areas such as the approaches to the English Channel and off northwest Scotland - both habitats of various beaked whales species and both areas where cetacean strandings are common.


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