What's Killing the Sea Otters

By Dan Cray

Los Angeles They're cute, furry, and when they're not chasing each other around kelp forests, they're floating on their backs like miniature teddy bears. Hunted nearly to extinction for their luxuriant fur--the thickest of any mammal's--the sea otters of California were making a comeback until they started mysteriously dying off. State wildlife officials recovered a record 281 dead otters last year, and this year looks to be even worse. Five or six wash up on California's beaches and rocks each week. In August alone, 28 dead otters were cast ashore, including an alarming number of full-grown females. "When we start losing breeding females," says veterinarian Mike Murray at the Monterey Bay Aquarium, "that's not a healthy population."

What's killing the sea otters? Sometimes the cause is clear: a shark bite, a bullet, an outboard motor. But about one-quarter of last year's fatalities have been traced to a pair of protozoan parasites, Toxoplasma gondii and Sarcocystis neurona, that are known to breed in cats and opossums. Could sea otters be dying because California cat owners are flushing used litter down the toilet?

State legislators were sufficiently convinced of the threat to pass a bill--signed into law last week by Governor Arnold Schwarzenegger--that raises the maximum fine for harming a sea otter to $25,000 and requires that all cat litter sold in California carry a warning label advising cat owners not to dump their pet's droppings into toilets or storm drains.

But cat litter is only a small part of the problem. Thorny-headed worms dropped into the ocean by seabirds are known to be killing otters, as are toxic algae blooms triggered by urea, a key ingredient in fertilizer. And sea otters, because they feed on shellfish that tend to accumulate whatever floats their way, are particularly susceptible to PCBS and other man-made pollutants.

Sea otters are not the only species harmed by ocean pollution, of course, but they are easier than most to study. They sit at the top of a food chain that may extend less than half a mile from shore. "The sea otter is the canary in the coal mine for the coastal ecosystem," says Monterey's Murray.

Right now, Murray contends, that mine is looking pretty dark. While the state's otter population is holding steady at nearly 2,700, projections show that number should already have reached at least 13,000. The next step, say scientists, is to pinpoint--then shut down--the sources of runoff that are pouring toxins into the otters' playgrounds.

In this effort, the charismatic sea otter may be its own best friend. Marine mammal experts aren't always as sentimental about the sharp-toothed creatures as the public is--one expert referred to otters eating shellfish on their tummies as "buzz saws in a fur coat"--but no one doubts the value of the "aww" factor. "When you've been bitten by one, you don't think they're so cute," says Michelle Staedler, the Monterey Aquarium's sea otter research coordinator, "but then you look, and they're a big ball of fluff." [This article contains a complex diagram. Please see hardcopy or pdf.] Hunted Nearly To Extinction Russia's Peter the Great declared a monopoly on sable in 1697 and sent hunters to find sea routes to America.When Vitus Bering's expedition was shipwrecked in 1741, his crew killed sea otters instead. They returned with 900 luxuriant pelts, setting off the Great Hunt. When the otters were depleted, Russia sold Alaska to the U.S. SEA OTTER FUR Built for warmth 1 million hairs per sq. in. Guard Hair Underfur Trapped Air HUMAN SCALP 150,000 hairs total Before 1741, there were as many as 300,000 sea otters on the Pacific Coast. By 1900 only a few colonies remained

Historic range

Remnant colonies Now New Threats Emerge Industrial chemicals, algae blooms and other toxins linked to coastal pollution are among the sea otter s new enemies. The threat from feline-borne toxoplasmosis, a common danger to pregnant women, helped trigger California's new law

1 Cat eats rodent or bird infected with Toxoplasma gondii parasite

2 Parasite develops in cat's gut and its eggs are released in scat

3 Eggs travel through runoff or are flushed into sewers

4 Eggs end up in the ocean and are ingested by mussels, clams and oysters

5 Otter eats shellfish; eggs infect the otter's brain and organs and kill it

Sources: Sea Otter Alliance; David Jessup, California Department of Fish and Game