(Reuters) - A 40-foot (12-meter) gray whale washed ashore in Northern California this week, bringing to at least four the number of strandings during the marine mammal's migration season, wildlife experts said on Wednesday.
Researchers with the California Academy of Sciences were unable to perform a necropsy on Wednesday morning as the adult female rolled in the deeper surf along the shore in Half Moon Bay, south of San Francisco, said spokeswoman Haley Bowling.
The gray whale, which likely washed ashore on Monday, was probably too far decomposed for scientists to collect tissue samples, though they will study its bones to see if it was struck by a ship, Bowling said.
The cetaceans, one of just two whale species to have been removed from a U.S. endangered species list, give birth in Mexico's Baja California in the winter and migrate to feeding areas in Alaska in the summer, traveling along the U.S. West Coast in the spring, said Laura Sherr, a spokeswoman for the nonprofit Marine Mammal Center.
"This is the time of year when we see an increase in the strandings, because they are in the area," Sherr said.
The gray whale is among at least four whales that have washed ashore in areas popular with beach-goers, Sherr said.
A Sperm whale and a Humpback whale have washed ashore in Pacifica since April, and an orca came ashore in April in MacKerricher State Park near Fort Bragg, Sherr said.
The cause of death for the Sperm whale was not yet conclusive, though it appeared emaciated. The Humpback had damaged vertebrae, meaning it was likely struck by a ship. Preliminary findings suggested the orca, or killer whale, became entangled in fishing lines.
(Reporting by Eric M. Johnson in Seattle; Editing by Cynthia Johnston and Sandra Maler)