California's female otter population dwindles

MONTEREY, Calif. — Born 11 or 12 years ago, the sea otter known as Pink-White is a senior citizen in Monterey Bay. She spends her days near Lovers Point, diving for crabs, napping and grooming her luxurious fur.

Her muzzle has turned gray, yet she is healthy and fertile, and about to give birth to another pup, one of perhaps as many as nine she has mothered in her lifetime. She is a living landmark, adored by tourists and locals, her movements and eating habits tracked by biologists almost since she was born.

Floating in the kelp off Cannery Row seems a sublime life for a sea otter. But the waters of Monterey Bay are treacherous, even deadly, particularly for older females such as Pink-White, named for the colors of the identification tags attached to her flipper-like hind feet.

For reasons that have eluded scientists for several decades, California's sea otters have been struggling while most otter populations elsewhere have thrived. Now, however, scientists studying Pink-White and her kind believe they may be closing in on one of the most baffling mysteries involving endangered species in the United States.

The latest clue is in the deaths among females, especially those in the reproductive prime of their lives. Females more than 4 years old have a low survival rate in the heart of their range, between Santa Cruz and Big Sur, while males are doing fine, their populations growing.

Scientists say female otters, which spend much of their energy raising pups, seem highly susceptible to stress, unable to cope with altered conditions in the ocean off California's midsection, including infectious diseases spread by cat feces, as well as chemical pollutants and insufficient food.

For the past decade, dead otters have washed ashore at the rate of three or four a week. Recently they have been dying in alarming numbers. In one month last year, nearly 50 otter carcasses were found.

All this comes despite extensive efforts by scientists to comprehend why.

On an overcast Monday morning in late September, four wildlife biologists from the U.S. Geological Survey motored past the Monterey Bay Aquarium in a 20-foot Boston Whaler.

They were on the lookout for 14 otters, 11 of them females, fitted a year earlier with devices that record how often and how deep they dive, as well as their fluctuating body temperatures. The data are used to calculate how much energy the animals expend finding food.

The scientists' work has yielded details about the lives and deaths of California's sea otters. It is a labor-intensive effort, requiring hundreds of people, thousands of man-hours and millions of dollars.

A receiver on the boat beeped almost immediately, indicating that Pink-White was nearby.

To recapture the tagged otters, scientists must outnumber them. On this day, 10 researchers were in two dive crews and a transport boat, while five spotters were onshore. At the aquarium, a veterinarian and several assistants stood by with a fully equipped operating room, waiting to open up the otters' bellies and retrieve the data devices.

Biologists Dan Monson and Heather Coletti, from the Geological Survey's Alaska Science Center in Anchorage, buckled weight belts onto their diving suits and climbed overboard, moving 500 feet toward Pink-White with ultra-quiet, propeller-driven scooters, attached to 3-foot-wide nets.

Three hours after they had motored out, the divers finally caught quick-moving Pink-White. Entangled, the 46-pound creature frantically rolled and bit at the net. This was Pink-White's third time captured. The scientists know to avoid her teeth, which can rip open clams and chew through crab shells.

Once ashore, she was rolled from the aquarium's freight elevator into its animal health laboratory, where a technician held her down with a thick mat while veterinarian Michael Murray injected her with a tranquilizer. In minutes, she was out.

They measured her and took a blood sample to check for disease and contaminants. Initial blood work found nothing unusual, but more detailed results wouldn't be known for months. On the operating table, Murray made an incision and retrieved the data-collection device, a 3-inch cylinder. He left the radio transmitter — the size of a bar of soap — so she could still be located upon her return to the sea. Then he carefully stitched her back up.

Pink-White got one more injection, this one to wake her up, and was released back into the bay.

In eight hours that day, the team captured and released five otters.

Sea otters were abundant in California in the 1800s, numbering about 16,000. By 1900, they were thought to be extinct, but about 50 managed to survive in a remote cove off Big Sur. In 1977, they were declared a federally protected endangered species. Today, about 2,800 California otters exist — all descendants of those 50 survivors.

Scientists say if California's otters were thriving like their cousins elsewhere, in Washington, British Columbia and southeast Alaska, their numbers should have rebounded by now to their original 16,000. Populations elsewhere have grown by 17 percent to 20 percent per year. But in California, the growth rate was just 5 percent until the mid-1990s. Then their numbers began to decline.

In only one other area, Alaska's Aleutian Islands, are otters faring poorly. The culprit there appears to be killer whales, whose usual prey of sea lions and seals have mysteriously vanished.

In California, all scientists know for certain is that the problem "has something to do with a change in their environment," said Jim Estes, a Geological Survey scientist in Santa Cruz. A leading authority on sea otters, Estes began researching the California population 35 years ago.

Perhaps California's 25-fold increase in human population has made modern life "incompatible" with otters, Estes said. "I think it's a whole bunch of stuff nibbling away at the population," he said: disease, pollution, conflicts with fishermen and boaters.

For the last two years, California's otter population has increased, raising optimism among scientists. But Tinker found that only males were increasing in number. Females continue to struggle. This phenomenon may be worse than no increase at all because the stronger males tend to crowd out the females and pups that sustain the population.

California's otters seem to be waging a classic battle of the sexes over food, and the males are winning, Tinker said.

"Males travel much farther than females and thus have access to better food resources, which likely improves their survival," said Katherine Ralls, a senior scientist with the Department of Conservation Biology at the Smithsonian's National Zoological Park. Males are expanding their range southward toward Santa Barbara, where food is more abundant, while the females stay largely around Monterey, where they are "trapped" in an area with low survival rates, Tinker said.

Wildlife biologists, the Monterey Bay Aquarium and conservation groups have formed a federal recovery team to try to restore the health of California's otters, even though they acknowledge that they don't completely understand the threats.

"We don't have a smoking gun out there. I wish we did because then we could take action more affirmatively," said Michael Sutton, director of the aquarium's new Center for the Future of the Oceans.

Some conservationists insist that enough is already known to justify some action.

Jim Curland of the Defenders of Wildlife said steps that can be taken now include controlling urban and farm runoff that carries chemicals and bacteria into the ocean and educating people to stop flushing cat litter and chemicals down toilets and into storm drains.

"If we chip away at the things we can control," Curland said, "maybe we can make a difference."