Gray whales’ Pacific crossing leads to questions of origin

This Sept. 13, 2010 photo provided by the Oregon State University Marine Mammal Institute shows a western Pacific gray whale near Sakhalin Island in Russia. Research by U.S. and Russian scientists who tracked rare western Pacific gray whales across the Bering Sea and all the way to Mexico have led them to question whether they are a separate species or simply California gray whales expanding their feeding grounds. (Craig Hayslip/OSU Marine Mammal Institute via AP) This Sept. 13, 2010 photo provided by the Oregon State University Marine Mammal Institute shows a western Pacific gray whale near Sakhalin Island in Russia. Research by U.S. and Russian scientists who tracked rare western Pacific gray whales across the Bering Sea and all the way to Mexico have led them to question whether they are a separate species or simply California gray whales expanding their feeding grounds. (Craig Hayslip/OSU Marine Mammal Institute via AP)

By Associated Press April 16, 2015 4 min read

ANCHORAGE, Alaska (AP) – A study of the migration of rare western Pacific gray whales has led U.S. and Russian scientists to question whether they’re a separate population or simply California gray whales that have expanded their feeding grounds.

Researchers for decades have considered the two subpopulations to be distinct, with different territories and genetics.

California gray whales occupy mostly waters closer to North America, while the much smaller western Pacific gray whale population was thought to roam the eastern Asia coast.

Recently, scientists over two migratory seasons tagged western Pacific gray whales off Russia’s Sakhalin Island, hoping to discover exactly where they spend winters.

The scientists were expecting western whales to migrate to breeding and calving grounds somewhere in the south China Sea, said Bruce Mate, director of the Marine Mammal Institute at Oregon State University and lead author of a research paper published this week in the journal Biology Letters.