


"We know the problem is not one of reduced reproduction. It's one of elevated mortality," said Tim Tinker, a wildlife biologist at the USGS Western Ecological Research Center at the UC Santa Cruz Long Marine Lab.

Lab tests show the otters are primarily dying from disease carried by bacteria, viruses and parasites. Those organisms are found in sewage as well as urban and farm runoff that contaminates creeks and coastal waters, researchers have found.

And although the animals don't seem to be suffering from lack of food due to fluctuating ocean conditions, researchers say their nutrition is limited when they can't get their fill of their preferred prey - crabs, urchins, clams, abalone and mussels.

Pollution and overfishing reduce the food supply, as does heavy feeding in popular spots by the otters themselves. When the otters aren't able to get the proper food, they are less likely to successfully fight disease, scientists say.

The largest density of otters stretches from the Monterey Peninsula to Big Sur south to Morro Bay (San Luis Obispo County). The buoyant, whiskered mammals were once found from Baja California to the Oregon coast.

Fur traders, beginning in the mid-1700s, speared and shot them for their pelts. By the 1900s, the otters were thought to be extinct. It wasn't until the 1920s that a remnant colony was discovered along Big Sur when the state was excavating for a road.

The otters' numbers have been slowly rising ever since. But in recent years, the recovery has leveled off.

Researchers pay most attention to the average population numbers over a three-year period. Each season, they average the count with the two preceding years in order to minimize any year-to-year anomalies. For example, windy weather this year could have played a part in the lower count.

Still, the three-year average ending this spring shows the first drop in otter numbers since 1999.

The average ending in 2009 was 2,813 otters, compared with 2,826 the year before, a drop of 0.5 percent.

The decrease may seem small, but scientists are concerned that the population isn't healthy and growing.

Because there is much unoccupied potential habitat in which the otters could expand, scientists are perplexed as to why the otter numbers remain small. In Washington, a population that was reintroduced as recently as the late 1960s and early 1970s has grown by 10 percent to 20 percent a year.

In an odd finding, the big groups of males typically counted at the far ends of the range at the Santa Barbara Channel and near Pigeon Point south of Half Moon Bay in the last five years weren't seen in the survey between May 4 and June 11.

To researchers, it means that the otters aren't expanding along the coast as hoped. Those groups at the range's periphery are the ones that expand into new territory, Tinker said.

But the observation doesn't alarm scientists, he said, because the expansion is dynamic, with the males moving from the periphery to the center and back.

"It's not a smooth continuum. We tend to see expansion in spurts," Tinker said.

This year, scientists who conducted the census with binoculars and spotting scopes were from USGS, the California Department of Fish and Game, the U.S. Fish and Wildlife Service, and Monterey Bay Aquarium. Volunteers also helped with the count.

Allison Ford, director of the nonprofit Otter Project in Marina (Santa Cruz County), issued a statement Tuesday warning that the otters' survival is at risk from biological and chemical pollutants, a shortage of nutritious food, boat strikes, fishing gear entanglement and violence from humans.

"We used to think that a big oil spill was the only problem we had to overcome to save the otters," Ford said.

"That's still important, but in the meantime, we're constricting their range, putting them in contact with deadly chemicals, and booby-trapping the waters. It's obvious that something more needs to be done."

About sea otters




Behavior: Use tools for feeding; spend hours grooming to keep fur waterproof by coating it with skin oil. Males and females usually stay in separate groups.
