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.
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."
This kind of basic observation of how whales spend their time underwater has only become possible in the past few years, with the development of new tags, says Ari Friedlaender, a marine ecologist at Duke University in Durham, North Carolina, who studies whales. "This is a really strong piece of work, to show that you can describe what these whales are doing in a very basic way" and then apply it to conservation, he says. "Right whales aren't going to change their foraging behavior. Even if they do, it's not for the right reasons. So we need to be the ones that are responsible for our actions. ... We can do things differently to make sure we don't hurt these animals."
North Atlantic right whales are already getting a lot of help. Since 1999, ships plowing through right whale habitat have had to slow down during the time of year when the whales are around. In the southeastern United States, planes spot the whales and warn ships; near Boston, buoys listen for right whale calls. These measures are helping the whales. "We're gaining ground, which is much better than where we thought were 10, 15 years ago," says Moira Brown, a whale biologist at the New England Aquarium in Boston, who was not involved with the study.
"This kind of paper is suggesting a little bit more fine-tuning, that we can do an even better of job of figuring out where the whales are," Brown says. It might be possible for the buoys that listen to whales to also carry instruments that measure plankton, giving managers a better idea of where the whales are likely to be. "And the whales are doing their part, you know," she adds. "They're having calves."