The harbor seals in Hood Canal, a 60-mile-long fjord to the west of Puget Sound, seemed anxious. Some were quivering along the banks. A few squirmed out of the water and wiggled toward high ground, passing close to people onshore—surprising behavior that suggested something spooky in the waters below. Brian McLaughlin had never seen them behave that way. “I’m reluctant to anthropomorphize,” says the fish biologist for the Washington State Department of Fish and Wildlife, “but they looked really nervous.”
For good reason. Over several weeks, about half the harbor seal population in the canal—700 salmon-fattened mammals—had become lunch. During the winter of 2003, 11 killer whales—orcas—did something marine mammal scientists say is without precedent. A newly formed pack of them swam into this harbor haven and ate all seals, all the time for two months straight.
One of the killer whales, a supersize male dubbed T-14, was a well-known local. He had been captured in Puget Sound in 1976 as part of an operation to supply orcas to aquariums. After a public outcry, he had been released, but not before a temporary transmitter was attached to his dorsal fin, which created a pair of identifying scars. The others with T-14 were interlopers from the north. Scientists knew all 10 of them—a male and three female-led family groups of four, three, and two—from the waters off northern British Columbia and southeastern Alaska. They had not been seen before with T-14.
The eight-ton predators had become a gang, an aquatic Hells Angels that hunted cooperatively, skulking among the five main sites in the canal where seals haul themselves out of the water to rest. Every day, scientists calculated, each of the 11 killer whales may have eaten one or two seals.
Then at noon one Monday in March, the orcas simply swam under the floating bridge at the north end of Hood Canal and disappeared into Puget Sound. Now scientists are hoping they’ll come back. “Why these animals stayed together so long in Hood Canal is a mystery,” said John K. B. Ford, one of the world’s leading researchers on orca behavior and a marine mammal scientist at the Canadian government’s Pacific Biological Station on Vancouver Island. “Their stay is an unusual opportunity to look at predation and how it might affect populations of the marine mammals they eat.”
Killer whales—icons of the Pacific Northwest’s environmental movement—are behaving badly. The beasts that inspired Free Willy, the children’s movie about a lovable orca held by an evil marine-park owner, seem to have developed untoward dining habits in the last half century. Long known as highly skilled group hunters, cooperatively stalking fish and marine mammals from Alaska to Antarctica, from Argentina to Iceland, they appear to have nearly wiped out regional populations of ocean mammals in both the Northern and Southern hemispheres.
• In the Aleutian Islands off Alaska, killer whales may have decimated entire colonies of sea otters.
• In coastal Alaska, orcas are a prime suspect in the otherwise unexplained disappearance of 80 percent of Steller sea lions over the past three decades.
• In the Northern Pacific and the southern Bering Sea, killer whales have been linked to collapsing populations of fur seals and harbor seals.
• In Antarctica, they are the plausible cause of sharp declines of southern sea lions and southern elephant seals.
• Also in Antarctica, orcas may be a factor in a purported dramatic reduction of minke whales.
In short, some orcas appear to have stepped up their appetite for certain marine animals. The likely cause, some researchers believe, is whaling. According to a new theory of predation—published late last year in the Proceedings of the National Academy of Sciences (PNAS)—humans sharply reduced the orcas’ main source of food in the 1950s with the postwar explosion of industrial whaling. “When that happened, some killer whales, which had been preying on big whales, had to do other things to make a living,” says James Estes, a research scientist in Santa Cruz, California, for the U.S. Geological Survey and coauthor of the PNAS article. “When the number of prey was insufficient to satisfy them—they do eat a lot—they moved on to something else, and they did it in a sequential way.”
First the orcas turned to large mammals—elephant seals in the Southern Hemisphere, Steller sea lions in the Northern. When those populations thinned out, the theory goes, they moved on to smaller prey, such as harbor seals and sea otters. Thus far, the orcas’ strategy seems to be working, at least from their point of view. While populations of sea lions, seals, and sea otters have disappeared, orcas are doing rather well. Although there are no official counts, the number of killer whales is believed to be relatively stable, at 30,000 to 80,000 worldwide.
Not everyone accepts this theory. Several prominent marine mammal scientists, not to mention animal protection activists, strongly disagree with the notion that orcas have become species-destroying marauders. They say the evidence is thin and argue that the theory could be used as an excuse to avoid reducing coastal pollution, which threatens all marine mammals, including orcas. “It is the Greenpeace nightmare,” Trevor Branch, a doctoral candidate at the University of Washington’s School of Aquatic Fishery Sciences, wrote in a presentation he gave last year to marine mammal scientists in Santa Cruz. “Antarctic minke whales are the banner-waving symbol of the antiwhaling movement, but so is Free Willy. What do you do when one is decimating the other?”