The question on everyone's mind lately has been: Where have San Francisco's famous sea lions gone? The answer might lie about 500 miles north of the Golden Gate, where an estimated 2,000 sea lions have recently arrived off the central Oregon coast.

"We've seen these huge pods out on the ocean - 200, 300 yards across - altogether a couple thousand sea lions," said Steve Saubert, co-owner of Sea Lion Caves, a private preserve near the town of Florence. "They were just here all of a sudden."

About 500 of those sea lions have moved into the caves themselves, about 300 of them in the past week, said Jim McMillan, an assistant manager at the park. There would be even more, Saubert said, but the 2-acre floor space of the cave limits the landing area.

Saubert, 66, who has been tracking marine wildlife and seabirds on the Oregon coast for most of his life, said that California sea lions, Steller sea lions, pelicans and other marine birds have been attracted to the area by an influx of cold water - 51 degrees the other day - and food, including herring, anchovies, smelt and squid. He believes this summer's El Niño event along the California coast pushed the food north and the wildlife followed.

That would coincide with the severe lack of herring in San Francisco Bay and along the Northern California coast, a population that usually peaks in January and February. Experts believe that has everything to do with the disappearance of sea lions from the bay and most notably from San Francisco's Pier 39.

On Oct. 23, the Marine Mammal Center counted a high of 1,701 sea lions at Pier 39 in San Francisco. On Nov. 21, volunteers counted 927. After Thanksgiving, there were only 20, and last week, a half dozen.

Kim Suryan, a biologist with the Marine Mammal Institute in Newport, part of Oregon State University, said she's been tracking the arrival of California sea lions and Steller sea lions at Sea Lion Caves and a haul-out area at nearby Heceta Point since 2005.

"This year, there's definitely more animals, probably a couple more thousand, than we've seen in the past couple years," Suryan said. "It's the talk of the town around here. A lot of people have noticed all the sea lions."

Back in California, several other areas have had similar en masse departures.

At Monterey's Fisherman's Wharf, the number of sea lions declined from 500 to 100 in the past two weeks, according to charter fisherman Chris Arcoleo at the wharf. At the mouth of the Russian River, where 250 to 300 sea lions often congregate, Michaela Daniels, who works at the nearby Jenner Inn, said she didn't see a single sea lion on a hike there this week. "There's nothing for them to eat," she said.

At the Farallones

One location with no apparent change is the Farallon Islands offshore of San Francisco.

"Everything is pretty much normal," said Mary Jane Schramm of the Gulf of the Farallones National Marine Sanctuary. She said scientists who work at the Farallones are seeing plenty of sea lions, murres, gulls and other wildlife. They believe the sea lions there are feeding on shrimp, squid and sardines.

"Sea lions are opportunistic feeders," Schramm said. "We're in an El Niño phase wherein all bets are off and the rules are suspended. El Niños sometimes induce wildlife with narrow temperature tolerance to shift northward."

Hippo Lau, a San Francisco fisherman, said the combination of warm water and lack of herring has sent the sea lions north.

"The herring is why the sea lions have been in San Francisco in the first place," Lau said. "For 20 years every winter, the commercial herring netters would just take the eggs from the females, then dump the bodies and discard the males with them. The sea lions would just lounge around and gorge whenever it happened." That has stopped this winter, he said.

Without being told large numbers of sea lions had been located in Oregon, Lau theorized the sea lions would be "up farther north, looking for herring. Part of it is the warmer water."

Up in Oregon

Sea Lion Caves is 11 miles north of Florence on the central Oregon coast. It is a cavern where tide waters enter its floor. Marine mammals and shorebirds use it as a resting area and for protection from storms and rough seas. Outside the cave is Lost Beach, near Heceta Point (named after explorer Bruno Heceta), which is not accessible by vehicle and provides an overflow resting area for sea lions when the cave is full.

Saubert said sea lions started arriving in large numbers in late October and the procession of arrivals never stopped. He sighted 40 brown pelicans a week ago, he said, and that "is real unusual for January here." They too follow the food, he said.

The abundant sea lion population in this area has created a micro-ecosystem where wildlife flourishes, Saubert said.

"What I think is happening is the sea lions follow the food supply," Saubert said. "Now we have all these sea lions here. They eat fish and their waste goes to the bottom. That fertilizes the marine food chain. You get plankton and brine shrimp, and that brings in the small fish and the whales. The small fish bring in the seabirds and the bigger fish. So the sea lions have plenty to eat and the cycle starts over again." Upwelling, a trigger for the marine food chain set off by winds out of the northwest, is often significant here.

The missing sea lions of San Francisco, Monterey and the Sonoma coast did not end up in Humboldt or Del Norte counties on California's north coast, said Bob Farrell, a marine lieutenant for the Department of Fish and Game based in Eureka, adding credence to the theory that they continued moving north.

They're welcome

Wherever they land, they will most likely be welcomed. Sea lions are charismatic animals that often seem to behave like big dogs. Their expressions and behavior have turned them into a huge tourist attraction at San Francisco's Pier 39 and their disappearance alarmed many. The hope is that they will return when water temperatures return to normal, bringing the herring and other cold-water fish back, as well.

The organization Tagging of Pacific Pelagics, better known as TOPP Census ( www.topp.org), tags and tracks the ocean migration of several species, including sharks, albatross and sea turtles, but has not tagged a sea lion for study this winter season.

"The sea lions are not tagged and tracked," said Jim Oswald at the Marine Mammal Center. "All we can guess, their goal at the core, is to find food."