Thousands of California sea lions started showing up in December at Sea Lion Caves, a popular tourist draw because of the Stellar sea lions living in the caves.
The California sea lions appear to have made the trip because of an abundance of anchovies at the Oregon site, 11 miles north of the town of Florence.
Scientists say there is no way to say how many of the newcomers came from Pier 39, where the numbers fell from a peak of 1,701 in October to just 20 by the end of November. But it is likely some did, since they easily swim 100 miles a day searching for food between Mexico and Alaska.
Some of the California newcomers came into the cave, but most seem to prefer a nearby rocky beach.
Kim Raum-Suryan, a biologist at the Hatfield Marine Science Center in Newport, noticed the number of California sea lions at Heceta Head had doubled to some 5,000 in December and, like other scientists, figures the simple answer is food.
"My gut feeling is it has something to do with the (ocean warming) El Nino conditions off California, which is driving prey and sea lions up north," she said.
There are fewer herrings in San Francisco Bay, and a general decline in sea lion food off California last summer triggered a die-off of young sea lions making the transition from mother's milk to fish.
Meanwhile, anchovies have been plentiful in Oregon waters - so plentiful that brown pelicans that normally winter in California are also hanging around, said Bob Emmett, a fisheries biologist for NOAA Fisheries Service in Newport.
