Right Whale Roadkill

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Right whales are said to have been the "right whale" for whalers to hunt because they're slow movers and they're close to the coast. Unfortunately, they've turned out to be right for something else too: getting hit by ships. A new study finds that in Cape Cod Bay, right whales hang out just below the water's surface—invisible to any watchers on ships—in patches of food. The new information could help scientists and managers figure out better ways of keeping whales from getting run over.

Right whales are said to have been the "right whale" for whalers to hunt because they're slow movers and they're close to the coast. Unfortunately, they've turned out to be right for something else too: getting hit by ships. A new study finds that in Cape Cod Bay, right whales hang out just below the water's surface—invisible to any watchers on ships—in patches of food. The new information could help scientists and managers figure out better ways of keeping whales from getting run over.

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The waters around Boston are thick with whales—and ships. Endangered North Atlantic right whales visit Cape Cod Bay, the body of water encircled by Cape Cod's curled arm, every spring. The whales are there to suck down copepods, crustaceans about the size of a sesame seed. In the past 30 years, five right whales are known to have been killed by ships in and around Cape Cod Bay. Five deaths in 3 decades may not sound so bad, says Susan Parks, a biologist at Pennsylvania State University, University Park, "but if you have three or 400 individuals and a relatively low population growth, ... people have done studies that have shown the loss of a single reproductive female could tip the scales for this population."

To find out just what whales were doing that made them so vulnerable to ships, Parks and her colleagues tagged whales in Cape Cod Bay in April of 2009 and 2010. They stalked their targets in a small boat, with Parks balancing a nearly 17-meter-long carbon-fiber pole with an electronic tag on the end. "You just wait behind them until they come up to breathe," she says. When the whale's broad back appeared, she smacked down the suction-cupped tag.

The idea was for the tag to stay on for a day and a night, but the whales didn't cooperate. They jackknife while feeding, which makes some of the suction cups pop off. "And then right whales are really social, so every afternoon pretty much every tagged whale we thought was going to get a tag into the night would join other right whales and they'd roll around and touch each other and the tag would pop off," Parks says. "It was really frustrating."

But she did get data from 13 tagged whales in the daytime. And while one boat followed the tagged whale, another toured the area, towing an instrument that uses sound waves to measure copepods in the water and occasionally sampling to identify the copepod species and see where they were.

Parks found that the whales spent the majority of their time with their backs between 0.5 and 2.5 meters below the surface. They kept their mouths at the same depth as the thickest patches of copepods. That suggests the whales are very good at finding their food—and at putting themselves in the worst position for ship strikes. A black whale approximately 2 meters below the surface is easy to hit but invisible from the bridge of a large ship. "Just knowing right whales are in the area was one thing," Parks says. "Knowing that they're in the area and you're not going to be able to see them during the day was something we wanted to point out to people."

Article continues: http://news.sciencemag.org/sciencenow/2011/08/right-whale-roadkill.html?rss=1