VICTORIA, Canada — The orca is a master predator. He glides like a torpedo, his 6-foot dorsal fin slicing through the surface of the sea. He hunts down a seal, rams it repeatedly with his tail and drowns it.
These wolves of the sea stand unrivaled at the top of the food web. But their rank in the ocean's hierarchy has given them another extraordinary--and perilous--distinction:
They appear to be the most contaminated animals on Earth.
The concentrations of industrial chemicals in orcas, or killer whales, off Washington state and Vancouver Island are the highest found in any living mammal, according to marine scientists. The poisons, subtle but insidious, have built up in their bodies to dangerously high levels.
Stars of Hollywood films and marine amusement parks, these black-and-white creatures are icons of the Pacific Northwest and British Columbia. On a typical summer day, hundreds of tourists and boaters set sail in hopes of spotting them.
Lately, though, there have been more whale-watching vessels than whales plying the picturesque waters between Seattle and Victoria.
The region's famed orca pods are shrinking. Government officials now say there is a strong chance that these descendants of Shamu, revered in native mythology as supernatural in their survival skills, could be named an endangered species.
The region's killer whales have been dying at a higher rate in the last five years, most disappearing without a trace. Nearly half of their calves die within months of their births.
Scientists wonder if the industrial poisons accumulating in their bodies are beginning to take a toll on their survival, impairing their ability to fight disease and to reproduce successfully.
Or perhaps the Pacific Northwest's whales, surrounded by nature lovers in yachts, kayaks and motorboats, are falling victim to the stresses of their own popularity. The decline in salmon--a diet staple for many orca pods--also may be harming them. Most likely, scientists say, the orcas are being harmed by a combination of the urban threats they face.
Because a generation of orcas spans 10 to 15 years, researchers warn that it is too early to tell whether the recent population decline is a temporary dip or a worrisome trend. In fact, this winter showed a promising development: three new calves, bringing the total population of the resident pods that frequent the San Juan Islands to 84.
But environmentalists worry that, if they wait for scientists to decipher the trends, it could be too late to save the whales.
Long-lived, elusive and intelligent, these animals have no predators. Nothing at sea is capable of killing a killer whale.
Except a human being.
Alarmingly High Contamination Levels
In the seaside town of Sidney, at the Canadian government's Institute of Ocean Sciences, Peter Ross opened a long-forgotten file one day in 1996.
He scanned the columns of data inside, and a number caught his eye.
250 parts per million.
At first, he didn't believe it. These were the worst concentrations of PCBs, or polychlorinated biphenyls, he had ever seen. And they came from live killer whales swimming in the scenic waters off Vancouver Island.
"My jaw dropped," Ross said. "I said, these animals are really hot."
Ross decided to investigate. He pulled the blubber biopsies of 30 more whales from a laboratory freezer and tested them for PCBs.
Ross, one of the world's foremost experts in marine mammal contamination, had reason to worry about the whales. While working in Europe a few years earlier, he had proved that PCBs weaken the immune systems of harbor seals. Animals with compromised immunity are more likely to become ill and die when exposed to disease or infections. European harbor seals experienced a massive die-off in 1988.
Ross realized, though, that the killer whales off British Columbia and Washington state made Europe's seals look pristine.
His research has shown that male killer whales contain as much as 15 times more contamination than the seals that suffered suppressed immunity.
At those concentrations, the whales "greatly exceeded many toxic thresholds for mammals," Ross said. Disruption of the whales' immune systems and reproduction is likely, since, he said, there is no reason to believe that PCBs' effects on whales are different from effects on seals.
Environmental agencies have known for years that the Seattle area's Puget Sound is tainted with PCBs. But no one had suspected that the poison was harming the killer whales because the San Juan Islands, where they mostly live, are miles away from any industrial dumps.
"The concentrations in the orcas are surprising, in part because they visit the Seattle area and other urban bays infrequently," said Scott Redman, science coordinator of the Puget Sound Water Quality Action Team, an arm of Washington state government. "Most of their fish come from less contaminated areas."
Indeed, the local PCB contamination is by no means extraordinary.