Fourth whale found dead along California coast

A 40-foot dead whale has been found along the Northern California coast, bringing to four the number that have been discovered in the past month.

The gray whale carcass was discovered on Monday near Half Moon Bay, about 30 miles south of San Francisco, KNTV reported.

On May 4, a 42-foot female humpback whale was found. A 48-foot sperm whale was found on April 14, both in the same general vicinity.

An orca, or killer, whale carcass was also found near Fort Bragg, 200 miles north in Mendocino, on April 18.

Scientists haven't been able to determine a cause of death for any of the animals.

Because all four are different species and because this is the time of year when whales are migrating along the California shore, they are probably not linked, said Jim Covel, director of guest experience at the Monterey Bay Aquarium in Monterey, Calif.

Gray whales have been migrating up from their birthing grounds in Mexico since late February.

"They haven't been eating much for the last several months, and a certain number of them just run out of gas," he said.

The sperm and humpback whales typically travel about 70 miles off shore, so they wouldn't have been in the same region along the coast when they died, making a problem in the area unlikely, he said.

All the whales are headed to summer feeding grounds in Alaska.

Because some whale populations are rebounding after enduring decades of depredation by hunters, there are now higher numbers passing along California each year. That could account for more frequent encounters with living, and dead, whales.

"Certainly the number of humpback whales is increasing at a pretty healthy rate, so we may be seeing more mortalities," Covel said.

Boat strikes are also a problem for whales up and down the coast, but usually they're relatively easy to spot, leaving tell-tale signs on the animal.

The danger has been lessening in the past few years as the national marine sanctuaries work with commercial shipping to move shipping lanes and slow traffic down, he said.

"When these large commercial vessels are moving at a pretty good clip, by the time the whales detect there's a ship there it's too late, they can't get out of the way," he said.

Slowing the ships down gives the whales time to react.

All of the carcasses were inspected by the network of whale-stranding experts that exists up and down the coast. Scientists come out to inspect and take tissue and sometime bone samples to try to determine the cause of death and for research purposes.

Once that's done, the carcasses are buried as quickly as possible because of the smell.

"Usually by the time they take it to the beach they've been dead a few days," Covel said. "By then, they've ripened quite a bit."