Chemicals Tainting Orcas' Dinnerby Robert McClure
The Columbian, April 5, 2006
More PBDEs seen; adults often share fish with young
The mother orca snags a big chinook salmon, bolts for the surface and chomps it in two. She leaves half for her baby.
It's a newly discovered behavior of Pacific Northwest killer whales, one that may help explain how young orcas survive when salmon runs are lean, marine scientists meeting in Seattle revealed Tuesday. In effect, the parents appear to be allowing themselves to starve at about the same rate as their children -- although father orcas give up far fewer fish than do the mothers. And this sharing may explain why orcas stay with their families for life.
However, scientists said, the salmon that nurture those baby orcas increasingly appear to be delivering a dose of chemicals that skew orcas' immune and reproductive systems -- chemicals the Washington Legislature recently refused to ban.
These fire-resistant chemicals, known as PBDEs or polybrominated diphenyl ethers, are still at much lower levels in the animals than the previous generation of fire-resistant chemicals, PCBs, or polychlorinated biphenyls. But the concentration of the new chemicals will surpass those of the old ones in 15 to 20 years, said Peter Ross of the Canadian Department of Fisheries and Oceans.
The two sets of long-lived chemicals in combination pack a one-two punch, Ross said in an interview Tuesday.
"If you get that in a fetus, you may not see proper brain development," he said. "You could get adults that are quite diminished in a number of ways."
The revelations came at a science conference sponsored by the National Marine Fisheries Service, which last year declared the orcas in need of protection under the Endangered Species Act and is now searching for ways to protect them.
Ross also has been studying harbor seals, which like orcas are mammals but which carry lighter burdens of both sets of the chemicals PBDEs and PCBs. In seals, Ross has measured decreased levels of the thyroid hormone that regulates a vast array of bodily functions.
People with depressed thyroid hormone may feel kind of blah -- fatigued, unable to function right. Orcas, seals and laboratory animals exposed to PCBs and PBDEs show the same deficits in the thyroid hormone.
"It doesn't matter if you're a killer whale or a human or a mouse or a guinea pig -- you've all got thyroid hormones," Ross told the scientists. "You've all got the same kind of immune system."
The seals closest to Seattle, in south Puget Sound, are the ones showing the highest concentrations in the Northwest of the fire-resistant chemicals, Ross said.
Two forms of PBDEs have been banned in Europe. The sole U.S. maker of PBDEs, Chemtura, has voluntarily stopped making them. A third form is still in use. In the legislative session that ended last month, a bill to phase it out was defeated after industry lobbying.
The chemicals have been used in a wide array of consumer products, including carpets, computers and cars.
The industry argues that the remaining chemical is not mobile in the environment, isn't very toxic and can't be taken up well by mammals.
"We know those statements to be false," Ross told the scientists.
In an interview, Ross said studies in Europe and the Midwest suggest that PBDEs are not as stable in the environment as PCBs, and the form that is still in production may be able to break down to the forms already pulled from the market.
Efforts to reach Chemtura on Tuesday were not successful.
The new research on the sharing of food by orcas came from Canadian researcher John Ford, who said the food sharing occurred in about 75 percent of the feedings witnessed by Department of Fisheries and Oceans researchers.
Mother orcas in those feedings were most likely to share fish, doing it about 90 percent of the time. Male orcas did so about 20 percent of the time. But juvenile orcas, adults without children and adolescents also shared.
"There's rampant sharing at all levels," Ford said.
Overall, a slew of evidence presented Tuesday suggests that orcas particularly target chinook salmon, even when there are many more sockeye and chum available. And Ford showed how when chinook abundance wanes, deaths of the orcas rise.
However, the sharing of fish provides an interesting twist, Ford said. While researchers would expect more young orcas to die when the fatty and nutritious chinook vanish, the deaths are distributed evenly between the older and younger orcas, he said. So, he said, scientists are thinking that the adults are sharing with the children, even at the expense of their own health.
"They're routinely sharing prey that they could easily swallow whole without batting an eye," Ford said.
"I think it plays a big role in their society. The reason they stay together for life, which is so unusual, may be related to sharing," he said. "Because they are such a tightly closed social unit, they need to work collectively and collaboratively."
Peter Ross of Canada's Department of Fisheries and Oceans and Rob Duff of the Washington Department of Health will give a talk tonight, "Toxics In The Mammals Of Puget Sound: Orcas, Seals, and Humans." Sponsored by a number of government agencies and private foundations, the talk is from 7 to 8:30 p.m. at Town Hall, 1119 Eighth Ave. Admission is $15 at the door.
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