Defenders Magazine

California's Sea Otters

Sink or Swim?

By Michael Tennesen

© James D. Watt/www.seapics.com

At the end of an old pier in San Simeon Cove, a crescent-shaped bay on the central California Coast, Brian Hatfield scans the waters with his spotting scope. Noticing motion in the kelp beds south of the pier, Hatfield, a biologist with the U.S. Geological Survey, zeroes in on the action.

There he sees a sleek, brown female otter diving over and over in the water, searching for sea urchins, shellfish and other food. Nearby, her young pup watches, clumsily trying to imitate mom’s dives.

Hatfield notes the otters on survey maps that he carries with him. These entries are part of an official, semi-annual count of southern sea otters along the California coast that he coordinates. With the help of about a dozen other land-based observers and several plane-based survey crews, Hatfield is attempting to get an accurate picture of the population of this threatened species.

Hatfield and the other observers will eventually count 2,825 otters on this survey—a 13 percent increase over the spring 2003 tally, and the second annual rise in southern sea otter numbers. After nearly a decade with no growth in the sea otter population, Hatfield says the recent counts make him optimistic. “But the increase seems to be due primarily to increases in areas traditionally inhabited by males,” adds Hatfield. “We’d feel better if we saw more females.”

Jim Curland, a California-based representative of Defenders of Wildlife, puts it more succinctly. Noting that sea otters still suffer from habitat loss, entanglement in fishing gear and many fatal diseases, he says “we’re not out of the woods yet.”

Sea otters are among the largest members of the weasel family, but among the smallest of the marine mammals. Although their larger sea-going counterparts rely mostly on fat to stay warm, sea otters rely on a thick coat of fur. They spend large amounts of time in the water preening it, fluffing it up and even blowing air into it, to help insulate themselves from the cold water.

These charismatic animals are found only in the north Pacific Ocean, where they live along rocky shorelines and sheltered coves. They once ranged from as far south as Baja California to as far north as Alaska and Russia. Scientists estimate that several hundred thousand sea otters thrived before commercial fur hunters began harvesting them in the mid-1700s. By 1911, when the fur trade was halted, only a few hundred animals were thought to have survived.

The southern, or California sea otter (one of three subspecies), was believed to have disappeared in the early 1900s, but a small remnant population was subsequently discovered living off the Big Sur coast. That group was the nucleus of a population that has expanded in fits and starts off the California coast during the past several decades.

Sea otters have voracious appetites, consuming the equivalent of 25 to 30 percent of their body weight each day, according to Jim Estes, another biologist with the U.S. Geological Survey. For an adult male, that can translate into as much as 20 pounds of seafood per day. But this feasting has benefits for the coastal areas where otters live. Sea otters eat sea urchins, which, if allowed to multiply unchecked, would destroy kelp forests. These forests of seaweed provide vital food and shelter for fish and other aquatic creatures, and help protect the coastline from erosion. When otters decline, kelp forests suffer, and with them, a host of other species loses out. Because sea otters play such a pivotal role in the lives of so many other creatures, scientists refer to them as a “keystone species.”

Although otters are now protected from hunting and recent surveys have shown their numbers slowly edging up in the last two years, threats to the animals still exist. One such challenge is fishing nets, in which the curious and hungry otters get snared. Gill nets—single-walled nets made of nylon or mono-filament that hang like curtains in the water—alone were killing 80 to 100 sea otters per year off the central California coast in the 1970s and early 1980s. Since then, thanks in part to pressure from Defenders and other conservation groups, California officials have placed restrictions on gill netting in otter habitat, and entanglement deaths have declined.

Pollution is also a problem, as was graphically illustrated in the aftermath of the oil spill from the Exxon Valdez in Alaska in 1989. Not wishing to see a repeat of this environmental tragedy off the coast of California, Defenders and other conservation groups have been trying to get the federal government to retire permanently some of the offshore oil and gas drilling leases in the state.

Although not a direct threat to California’s sea otters, orcas (or killer whales) are prime suspects in the recent declines in another subspecies, the northern sea otters, in southwestern Alaska. Estes speculates that killer whales were forced to find other prey when whaling boats decimated whale populations in the Pacific after World War II. He believes that killer whales first turned toward harbor seals, then Steller sea lions, and now northern sea otters in a domino effect initiated by over-whaling. “The population in southwest Alaska is looking very grim,” Estes says. “We could be looking at extinction in the next decade.”

Perhaps the biggest perils to California’s sea otters at present are diseases. According to Curland, “Annually, disease counts for up to 40 percent of sea otter mortality. That’s one of the highest rates of disease among all wild populations.”

When sick animals wash up on shore, they are brought to the Monterey Bay Aquarium and examined by staff veterinarian Dr. Michael Murray. “The sea otter is a tough animal,” says Murray. “They have to be in pretty dire straits before they are going to beach and let us approach them.” In recent years, Murray has found otters suffering from intestinal worms, bacterial infections and even fungal infections.

Otters may be more susceptible to these health problems because their immune systems are weakened by toxins. Monterey Bay, at the center of the California sea otter range, receives large amounts of pesticides and other toxins that wash off of nearby farms and urban areas. The contaminants are ingested by shellfish, which filter the water for their food. When sea otters eat these shellfish, they are often getting a magnified dose of the toxins. Pollutants may also lead to large blooms of algae in near-shore waters. Some of these algae produce domoic acid, which can be toxic to sea otters.

Another recent and surprising source of health problems for otters is domestic cats. In the past year, dozens of sea otters have washed up on California’s shores afflicted with parasites from cat and opossum feces. Wastewater containing the parasites is believed to wash down from the land into the ocean, where it is consumed by shellfish, which are in turn eaten by the otters.

Murray is alarmed by the prevalence of terrestrial diseases in marine species such as the otter—not only for the otters’ sake, but also for humans. “We share that near-shore environment,” says Murray. “What we’re doing to sea otters we could be doing to people.”

The Pacific waters contain many perils for the sea otter, but at least in California, this charming creature is showing its resilience. Says Hatfield, “The southern sea otter still has a lot of problems and we can't let down our guard, but the population appears to be increasing, and that’s encouraging.”

Michael Tennesen is a California-based journalist who writes frequently on environmental issues.