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Previously:

• Dead Gray Whale Near Point St. George May Have Been Attacked by Orcas

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Scientists have identified the orcas involved in an attack on a gray whale off Del Norte County that was captured on video and may have resulted in the whale’s demise.

That group of transient killer whales had been harassing gray whales in Depoe Bay, Oregon, about five days before the Crescent City attack, said Josh McInnes, graduate researcher with the University of British Columbia’s Marine Mammal Research Unit. Six days after the Crescent City attack, those same orcas had traveled back north and killed a harbor seal near Newport, McInnes said.

“There were four whales that we were able to ID from photographs,” he told the Wild Rivers Outpost. T73, her second offspring T73C2, and there was another roaming whale we know as T37A1, who’s a female that seems to go between different orca groups. And then we had an animal we believe is an outer-coast transient known as OCT516.”

On Tuesday, McInnes and his partner Chelsea Mathieson found themselves in the cabin of Harry Adams’ charter boat, the Onyx, headed to the scene of the April 15 killer whale-gray whale attack.

McInnes and Mathieson are wending their way from British Columbia to Monterey via North Coast communities like Fort Bragg and Bodega Bay in the hopes of collaborating with boat owners like Adams to learn more about transient orca distribution.

“We want to better understand the gray whale-killer whale dynamic,” said McInnes who, along with Matthieson, has been cataloging transient orcas. “There’s not as much coverage out here. The Northern California coast is very remote compared to the Monterey and Central Coast.”

Though the whales didn't get the memo that he was in town on Tuesday, spring is the time of year to see them, McInnes said.

Unlike the more well-known southern resident killer whales, who feed on salmon off the Washington and Oregon coasts, transient orcas prey on marine mammals, McInnes said. Harbor seals account for much of their diet, he said, but they also feed on sea lions and other whales.

The 28-foot long subadult female gray whale that washed ashore near Point St. George between April 15 and April 18 had fresh tooth marks on its body consistent with a killer whale attack, according to Dawn Goley, director of Cal Poly Humboldt’s Marine Mammal Stranding Program.

However, the animal was fairly emaciated and Goley said she and her students, who performed an internal and external investigation, were unable to determine a “definitive cause of death.”

On Tuesday, McInnes speculated that the opportunity to hunt a malnourished whale might have been too good for the orcas to pass up. The orcas may have broke off the attack because they felt the shallow waters they had driven the animal into was too dangerous, McInnes said.

Another unusual thing about the attack in Crescent City, McInnes said, is those transient orcas don’t often feed on gray whales.

“They’re not gray whale specialists,” he said. “Most of our sightings of that group have been in Southeast Alaska. They’re going after seals there.”

They’ve also been sighted in Southern Vancouver Island and around Washington where there is also an abundance of seals and sea lions.

“This is neat; it shows their diet varies considerably,” McInnes said.

Adams told the Outpost that the orcas were working the smaller gray whale like a ferris wheel, flipping it on its back trying to drown it. The water was about 80 feet deep when the orcas began worrying the gray whales. The orcas drove the smaller gray whale into about 38 feet of water before abandoning the attack, Adams said.

“I was telling my friends, I’m gonna go find the orcas attacking the grays,” he said. “It took me 10 days, but I found them.”

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