Scientists Seek Reasons For Orca Decline

Salmon runs have declined in most areas, and died out completely in others, and that has forced the whales to look elsewhere for food. What she suspects is they are finding it in the wrong place, on the bottom of the sea. If there aren't enough salmon to go around, the whales are probably eating a lot more bottom fish, which tend to have even higher concentrations of PCBs, she says. It also requires "a greater expenditure of energy" to dive to the depths where the bottom fish are found, thus pumping up the demand for food. And a mature orca can require 300 pounds of food per day.

It appears that the whales aren't finding enough salmon so they are being forced to dive for less satisfying food, and they are getting loaded with toxic chemicals.

"They're getting hit with a triple whammy," she says.

Dead Whale Offers Clues

Much of the evidence for that comes from an autopsy on a dead orca found in March of 2000. It had quite a story to tell.

"He was a 22-year-old male, and his body was ravaged with bacterial infection that he should have been able to fight off," she says. "It just completely got into every organ of his body and killed him."

Scientists think toxic chemicals did so much damage to the whale's immune system that it simply couldn't fight back what probably started out as a common cold.

Unfortunately, that's the only dead orca that has been found, she adds, leaving the scientists in the uncomfortable position of relying on "a sample size of one." It might seem like a dead whale should be a pretty easy thing to find, but the fact is "they don't just float up," Hawks-Johnson says.

The orcas of the Pacific Northwest are so closely monitored that if a missing whale turned up in the wrong pod, it would be immediately identified. The whales that are missing from the southern Puget Sound pods have never turned up anywhere, according to professional whale watchers, so they are presumed dead.

The new study launched by the University of Washington will seek to fill in some of the many gaps in what we know about the behavior of killer whales. Scientists will track the whales with a six-foot-long radio-controlled catamaran that is equipped with a fish finder that should tell if the whales are indeed getting most of their food from the bottom of the sea.

That will be useful along the coast of Washington, but the whales go somewhere else during the winter, and no one is certain where.

"Perhaps the most serious problem is what is happening offshore in the winter," says David Bain, an animal behaviorist who has studied orcas for 20 years. He dreams of building a robotic vessel that could follow the whales throughout the year.

In the meantime, scientists will rely on a tiny but well endowed catamaran to peer below the surface and eavesdrop on some magnificent animals that are in a great deal of trouble.

Lee Dye’s column appears weekly on A former science writer for the Los Angeles Times, he now lives in Juneau, Alaska.

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