Subscribe free to our newsletters via your
. Earth Science News .

Subscribe free to our newsletters via your

WHOI-Led Report Links Sonar To Whale Strandings

Scientists know so little about beaked whales like this adult because they prefer deep waters far offshore, where they can dive on one breath of air to depths of over a mile for up to an hour and a half, according to WHOI's Tyack. (Photo by Todd Pusser, taken under NMS permit 14241)
by Staff Writers
Woods Hole MA (SPX) Mar 18, 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.

The knowledge most critical to protecting these whales from risk of sonar involves measuring the threshold between safe and risky exposure levels, but until now it has not been known how beaked whales respond to sonar, much less the levels that pose a problem. "We know so little about beaked whales because they prefer deep waters far offshore, where they can dive on one breath of air to depths of over a mile for up to an hour and a half," said Peter Tyack, a senior scientist at Woods Hole Oceanographic Institution (WHOI).

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.

Tyack and his colleagues used two complementary methods to investigate behavioral responses of beaked whales to sonar: "an opportunistic approach that monitored whale responses to multi-day naval exercises involving tactical mid-frequency sonars, and an experimental approach using playbacks of simulated sonar and control sounds to whales tagged with a device that records sound, movement, and orientation," the researchers report in the current issue of the journal PLOS (Public Library of Science) ONE

That research team developed experiments to slowly increase the level of sonar at a tagged whale, to stop exposure as soon as the whale started responding, to measure that exposure, and to define the response. The experimental approach used tags to measure acoustic exposure and behavioral reactions of beaked whales to one controlled exposure each of simulated military sonar, killer whale calls, and band-limited noise.

"These experiments were very difficult to develop, and it was a major breakthrough simply to be able to develop a study that could safely study these responses," Tyack said. "All three times that tagged beaked whales were exposed experimentally to playback of sounds when they were foraging at depth, they stopped foraging prematurely and made unusually long and slow ascents to the surface, moving away from the sound.

Beaked whales use their own biosonar to find prey when they are foraging; this means that one can monitor cessation of foraging by listening for when they stop clicking. Once the researchers found that beaked whales responded to sonar by ceasing clicking, they were able to monitor reactions of beaked whales during actual sonar exercises on the range.

The research was conducted on a naval testing range where an array of underwater microphones, or hydrophones, covered the seafloor, allowing whale sounds to be monitored over 600 square miles.

"During actual sonar exercises, beaked whales were primarily detected near the periphery of the range, on average 16 km away from the sonar transmissions. Once the exercise stopped, beaked whales gradually filled in the center of the range over 2-3 days," they report.

A satellite tagged whale moved outside the range during an exercise, returning over 2-3 days post-exercise. "The combined results indicate similar disruption of foraging behavior and avoidance by beaked whales in the two different contexts, at exposures well below those used by regulators to define disturbance," the scientists report.

"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."

Share This Article With Planet Earth DiggDigg RedditReddit
YahooMyWebYahooMyWeb GoogleGoogle FacebookFacebook

Related Links
Woods Hole Oceanographic Institution (WHOI)
Follow the Whaling Debate

Memory Foam Mattress Review
Newsletters :: SpaceDaily :: SpaceWar :: TerraDaily :: Energy Daily
XML Feeds :: Space News :: Earth News :: War News :: Solar Energy News

30 whales stranded on Australian coast
Sydney (AFP) March 17, 2011
A pod of around 30 pilot whales became stranded on Bruny Island, south of the Tasmanian state capital Hobart, on Thursday, wildlife authorities said. Department of Parks and Wildlife spokeswoman Liz Wren told the Hobart Mercury newspaper that 12 of the whales were still alive with people on the beach trying to move them back into the water. "Preliminary reports indicate around 30 whales ... read more

Haiti's desperate tent dwellers pin hopes on election

UN atomic watchdog under fire over role in Japan crisis

Japan choppers, trucks douse stricken atomic plant

Mounting Japan crisis sparks exodus of foreigners

US boosts radiation monitors, allays fears in west

US checks Japan travelers, finds no harmful radiation

NY Times unveils plan to charge readers on the Web

US admiral 'optimistic' on Japan nuclear risk

Scotland plans largest tidal energy farm

'Open for business' Hawaii dismisses nuclear fears

Ethiopian dams on Nile stir river rivalry

Shallow-Water Shrimp Tolerates Deep-Sea Conditions

Wheels Up for Extensive Survey of Arctic Ice

Arctic-Wide Measurements Verify Rapid Ozone Depletion In Recent Days

Pace of polar ice melt 'accelerating rapidly': study

Soot Packs A Punch On Tibetan Plateau's Climate

Plasticity Of Plants Helps Them Adapt To Climate Change

Brazil clamps down on foreign land buyers

Natural Sequence Farming

Dairy Farmer Finds Unusual Forage Grass

Cuts could cripple US tsunami warning: Official

Tsunami alert system to be tested in Caribbean

Veteran rescuers stunned by Japan damage

Japan disaster dead, missing toll tops 16,600: police

UN says Abidjian attack may be crimes against humanity

Cameroon suspends Twitter for 'security reasons'

Over 500 flee restive Casamance flee to Gambia: UN

First protests in Guinea since Conde takes power

Study: More immigrant families are intact

Study: Neanderthals had control of fire

Age Affects All Primates

Brain Has 3 Layers Of Working Memory

The content herein, unless otherwise known to be public domain, are Copyright 1995-2010 - SpaceDaily. AFP and UPI Wire Stories are copyright Agence France-Presse and United Press International. ESA Portal Reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement,agreement or approval of any opinions, statements or information provided by SpaceDaily on any Web page published or hosted by SpaceDaily. Privacy Statement