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Large group of killer whales found off the coast of California: here’s why

Whale watchers on a boat off the coast of San Francisco saw an unusual sight last month: 24 orcas west of the Farallon Islands were frolicking together in what naturalists say appears to be a gathering of several different families.

Orcas often spend time along the central California coast at this time of year, especially in Monterey Bay, but they don’t usually show up in such large groups near the Faraglioni. The reason they’re here isn’t so pretty to contemplate: They’re hunting sea lions and gray whale calves that migrate up the coast with their mothers, and the method is “pretty brutal,” said Nancy Black, a marine biologist at the whale. observation team Monterey Bay Whale Watch and the California Killer Whale Project, which tracks individual killer whales.

“They come to this area because they have an advantage when they hunt gray whales,” said Black, who has studied orcas for 35 years. “Grey whales and calves have to cross Monterey Canyon. That’s the danger zone.”

Black is talking about transient or Bigg’s killer whales, a subset of the killer whale species that has a marine mammal diet that includes sea lions, young elephant seals, harbor seals, porpoises, dolphins, and the occasional blue whale, while the Southern resident killer whale, an endangered orca ecotype, eats salmon.

Transient killer whales range from Alaska to southern California and can be seen in central California year-round. But during calving season for gray whales, they head to Monterey Bay in large numbers because the canyon’s deepest waters are so close to shore, giving them the element of surprise.

“Mother-calf gray whales hug the shoreline. They travel along the kelp bed and that is their protection,” Black said.

Gray whales only get into trouble if they stray too far from shore. If spotted by killer whales, adult female killer whales are often in charge of the hunt. First, they separate the mother from the calf, then they lunge at the calf to injure it, throw themselves on top of it and grab its fins with their teeth to drag it down and finally drown it.

The slaughter usually lasts two hours, but Black once witnessed an attack that lasted 15 minutes from start to finish involving some “incredible” female orcas.

The orcas seen near the Farallones were located several miles beyond the islands near the edge of the continental shelf.

An unusually large group of several orca families was spotted near the Farallon Islands off the coast of San Francisco last month.  Orcas may come to the islands to feed on sea lions and seals, and spend time in Monterey Bay in the spring to hunt for baby gray whales.

An unusually large group of several orca families was spotted near the Farallon Islands off the coast of San Francisco last month. Orcas may come to the islands to feed on sea lions and seals, and spend time in Monterey Bay in the spring to hunt for baby gray whales.

Courtesy of Michael Pierson/Ocean Society

“We meet orcas maybe two or three times a year,” said Michael Pierson, a naturalist with the Oceanic Society, a nonprofit organization that offers whale-watching trips to the Farallon Islands from April through November. However, they typically see four to six whales instead of the 24 they saw in early May.

In addition to gray whales, orcas are likely to arrive at the Farallones at this time of year because this is when pregnant sea lions also arrive to give birth on the rocky archipelago. Last year, Pierson was leading an expedition when the older female orcas showed the younger ones how to round up the sea lions before devouring them.

Pierson realized it was a hunting lesson because the orcas continued to hold the sea lions in a tight group and wait to eat them until they approached islands where the pinnipeds might have had a chance to escape.

Suddenly, “You saw the females dive in and come out with chunks,” Pierson said. “The lesson is over. It’s lunch time.”

Female killer whales have been known to teach their daughters, granddaughters and even great-granddaughters how to hunt, Black said. Unlike other types of whales, they live past their reproductive years and continue to play an important role.

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