SCIENCEClint Eastwood may once have been mayor of Carmel, a town just south of here, but it's the whiskered mug of a different outlaw that stares out from postcard racks, brochures and storefronts along coastal Route 1. Whether posing in a blanket of kelp or taking a meal from sea urchin beds, the California sea otter has found celebrityhood.
Amazingly, just a century ago Russian fur traders were converging on California's shores to hunt the sea otter to near extinction. By 1912, nearly 200,000 of these animals had been slaughtered.
Today, tourists clamber after the California sea otter with video cameras and binoculars, and the state of California proudly takes a census of its otter population each year. The latest count is about 1,800.
Wildlife scientists, however, are skeptical about writing a happy conclusion to the saga of the California sea otter. It's no secret that the state's shellfishing industry is openly hostile to the slowly increasing numbers of these voracious creatures, which daily consume one-quarter of their body weight in abalones, clams, mussels, sea urchins, crabs, snails and octopuses. Hundreds of sea otters also have drowned in commercial fishing nets in the last decade.
Further, a major oil spill could severely reduce or wipe out California's otter population virtually overnight. Some experts say the question is no longer if a major oil spill - one similar in size to Alaska's 1988 Exxon Valdez accident - could happen along the California coast, but when.
"Sea otters are one of the most sensitive species that could be affected by a spill along the California coast," says Dr. Katherine Ralls, a research zoologist with the Smithsonian Institution's National Zoological Park. "Their status as threatened under the Endangered Species Act is an acknowledgement of the risk of a major spill."
In Alaska's Prince William Sound, scientists are monitoring the recovery of sea otter populations affected by the Valdez spill. Not all Alaskan otter communities were affected, and although an estimated 5,000 otters died, their overall population in Alaska was never in jeopardy. Alaska's otter population - around 200,000 - is much larger and spread over hundreds more miles than California's.
"Many people assume Alaska and California sea otters are identical," says Dr. Donald Wilson, a mammalogist at the Smithsonian's National Museum of Natural History in Washington, D.C. "Some argue that should California's sea otters die out, more could be brought in from Alaska to the California coast."
It was recently established, however, that Alaska and California sea otters are in fact, two different sub-species. Thus, should California's sea otter die out, it would mean the end of their sub-species. They could never be replaced.
Recent events, such as the crisis in the Persian Gulf, where the United States gets approximately 12 percent of its oil, have stimulated interest in petroleum deposits off the California coast, says Dr. Glenn VanBlaricom, an otter expert for the U.S. Fish and Wildlife Service in Santa Cruz, Calif. "While tanker traffic poses the greatest risk to the California's coast, an increase in offshore platform drilling would also add significantly to the chances of a large spill."
Years before the Exxon Valdez shrouded Prince William Sound in black crude, the U.S. Minerals Management Service sponsored studies to assess the impact of such a disaster on California's sea otter population. One such study, conducted by the National Zoo's Ralls and Dr. Donald Siniff, an ecologist at the University of Minnesota, revealed that, even under normal conditions, the life of these seemingly carefree marine mammals is precarious.
Ralls, Siniff and others tracked 40 otters in Alaska and 45 in California via small radio receivers implanted beneath the otter's skin. Survival rates, movement patterns and eating, foraging and reproductive habits were recorded.
"Although the sea otters we observed had a high rate of reproduction, we were surprised to learn so many otter pups in California do not survive to weaning," Rill says. In California, eight of 19 pups born to otters under observation did not survive weaning.
Recently, the number of otters drowned in fishing nets has been greatly reduced by new laws making it illegal to set nets near shore in waters less than 180 to 240 feet deep. These depth limits were based on data gathered by Ralls and Siniff that showed otters swim in deeper waters than previously supposed.
Sharks, gunshots, disease, parasites, pollution and storms also contribute to high otter mortality rates, yet an otter's odds for survival may differ according to its age and sex, Ralls says. "The survival of adult females seems quite high while adult males don't survive as well."
"Over the last decade, the population of California sea otters has been growing at a rate of 5 percent a year, which is low compared to the growth rates of sea otter populations elsewhere, which is 17 to 20 percent per year," Ralls explains. Any subtle change in coastal conditions might easily over-stress California's sea otter population, sending it into decline, she adds.
Ralls and Siniff also learned that sea otter movements could hamper management during a crisis.
"In general, we found that otters tend to stay within one-half mile to one mile of the shore line for an extended period and then suddenly move long distances," Ralls says. "Monitoring revealed that otters of all age and sex groups make a surprising number of long-distance movements at all times of the year."
Keeping otters out of oil-contaminated areas, then, would be difficult without putting them in pens. In addition, some researchers observed that otters transported to a new location may return home.
Dr. Thomas Williams, a veterinarian at the Monteray Bay Aquarium who worked to save otters during the Valdez disaster, notes that the Alaskan otters "not only became coated with oil, but their lives were destroyed by ingesting it."
In the 1930s, scientists were ecstatic when a small population of California sea otters was discovered living near Bixby Creek, Calif. Until then, they had been considered extinct. Somehow the steep cliffs and rocky waters of California's coast had protected a few of these animals from overzealous hunters. Today, scientists and others hope the otter's celebrity status will make people more aware of the pressures sea otters are currently facing in California and lead to efforts to assure they remain a permanent attraction of the California coast.