Scientists tracking a rare western Pacific gray whale were shocked last winter when the endangered animal left the Asian coast, crossed the Bering Sea and swam south along Alaska, British Columbia and the Pacific Northwest coasts.

Researchers are back in Russia to see whether the feat will be repeated by other Pacific gray whales.

A science team coordinated by the International Whaling Commission has attached satellite tags to five more of the highly endangered whales, according to an announcement by Oregon State University, which is taking part in the study. Researchers hope to tag 10 more whales before field work concludes.

Only about 130 western Pacific gray whales remain and little is known of their winter habits. They spend summers near Russia's Sahkalin Island. They face threats from offshore petroleum development, according to environmental groups.

Researchers last October were limited by foul weather to placing a cigar-size satellite tag on just one whale on the last day of field work. The 13-year-old male was dubbed "Flex." It spent more than two months feeding near Sakhalin Island before moving across the Sea of Okhotsk to the west coast of the Kamchatka Peninsula.

On Jan. 3, to the surprise of researchers, it began swimming steadily east across the Bering Sea. Eighty miles north of Alaska's Pribilof Islands, the whale turned south, and swam between Aleutian Islands into the Gulf of Alaska. It continued southeast to shallow coastal waters off Washington and Oregon. Its last confirmed location was Feb. 4 off Siletz Bay, Ore., where researchers believe the satellite tag fell off. The whale had traveled 5,335 miles over 124 days.

Bruce Mate, director of the Marine Mammal Institute at Oregon State University, told The Associated Press in January that little was known about the winter habits of western Pacific gray whales. One hypothesis was that they swam south down the Asian coast to the southeast China Sea. Tracking one to North America waters was "surprising everybody," he said in January.

Marine researchers later determined that Flex had crossed the Pacific at least once before. Researchers sent a photo of Flex to Cascadia Research Collective, a scientific and education organization based in Olympia, Wash., which matched the photo to a whale photographed in 2008 off Canada's Vancouver Island.

Mate is again part of the research team and is leading the tagging portion. He didn't immediately return an email from the AP on Wednesday.

The effort also includes scientists from the A.N. Severtsov Institute of Ecology and Evolution of the Russian Academy of Sciences and the U.S. National Marine Fisheries Service.

Like last year, the public will be able to track tagged whales through weekly updates posted in English at http://mmi.oregonstate.edu/Sakhalin2011 and in Russian at http://kit.sevin-expedition.ru/news/news-69.html . A tag on one whale was not completely attached, according to the Oregon State website, and may have fallen off.

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