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.