The Mercury News

Stranded killer whale mystifies scientists

Orca the third cetacean found dead in a week

- By Glenda Anderson

Marine mammal specialist­s descended on the Mendocino coast over the weekend to evaluate and collect specimens at a rare stranding of a 26- foot- long killer whale found dead Saturday north of Fort Bragg.

The male orca is the third cetacean to become stranded along the Northern California coast in less than a week. The others were a common dolphin, found dying early last week on a beach in San Gregorio and a sperm whale that washed ashore in Pacifica. The cause of the sperm whale’s death cannot be determined and the reason behind the death of the dolphin is pending a necropsy, but neither bore signs of trauma, such as being struck by a boat.

It’s also not yet known what killed the orca, but it’s apparently unrelated to the epidemic of dead and dying sea lions being found along the California Coast.

The sea lions are starving while the whale, found on a beach at MacKerrich­er State Park, was in good shape and had a stomach full of harbor seals, said Dr. Shawn Johnson, head of veterinary science at the Marine Mammal Center in Sausalito.

“He had recently had a big meal,” Johnson said, adding there were up to six harbor seals in its stomach.

A rope with crab pot buoys that was attached to the whale’s tail initially was suspected in the death but was ruled out, at least as a primary cause of death, because it apparently had not prevented the whale from swimming and feeding.

But the rope indicated the animal had at some point become entangled in fishing equipment, something that always is of concern, Johnson said. “It’s sad to find these marine mammals being negatively impacted by people,” he said.

It’s the first time he can recall the Marine Mammal Center responding to an orca entangled in crab pot ropes. It’s also just the sixth time in 40 years that the center has responded to a call about a stranded orca, Johnson said.

But the incidence of marine mammals becoming entangled in fishing equipment is far too common.

An estimated 300,000 cetaceans are killed worldwide each year by fishing nets, according to Whale and Dolphin Conservati­on, an internatio­nal group that advocates for the animals.

The quest for the cause of the orca’s death is continuing microscopi­cally.

Organs and other were collected tissue by people working with the Marine Mammal Center, the California Academy of Sciences, Humboldt State University’s Marine Mammal Stranding Network and the Noyo Center for Marine Science.

The whale carcass also has been removed from the beach. The Noyo Center plans to strip the flesh from the bones and eventually display the skeleton alongside a 73- foot blue whale retrieved from a cove south of Fort Bragg in 2009, said Executive Director Sheila Semans.

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