An uncommonly large grouping of orcas for Northern California — roughly two dozen killer whales — were spotted by a whale-watching tour off the coast of San Francisco last month, likely gathered together to celebrate a successful hunt for sea lions or seals.
"I screamed 'orca!'" recalled Michael Pierson, an Oceanic Society naturalist leading the tour, after noticing "those distinct dorsal finds poking out of the water."
"It was really, really special," Pearson said in an interview Wednesday.
The big group of whales was seen on May 7 near the Farallon Islands, about 28 miles (45 kilometers) west of San Francisco. Killer whales are more commonly found around the deep ocean canyon beneath Monterey Bay — about 75 miles south of the city — and can be spotted anywhere from the coastline to just 5 miles offshore, according to Nancy Black, a marine biologist and owner of Monterey Bay Whale Watch.
It's easier for whale-watching tours to see them in Monterey Bay because the canyon is so close to the beach, while the Farallon Islands require a miles-long boat ride from San Francisco, and the water still may not be deep enough there, Black said.
"They're the whale that most people want to see when they go whale-watching," she said, "you just don't know when they're going to be around."
Black, who is also the director of the nonprofit California Killer Whale Project, said she's seen larger groupings of orcas than last month's two dozen but added that any sighting is special. As she spoke, she watched five swim together in Monterey Bay.
The Oceanic Society regularly does tours to the Farallon Islands — which include collecting data for scientists and conservationists — and spring is migration season. Pierson and the boat's captain, Jared Davis, decided to try a different route on May 7 to head out over deeper water.
When spotted during Farallon Islands tours, the orcas are usually in a family group of three to six whales. They typically range from Baja California up the West Coast and Canada to Alaska.
Last month, however, the tour stumbled across several family groups congregating together, for a total of 20 to 24. They were likely near the islands because it's where pregnant sea lions and seals give birth this time of year — and the mammal-eating whales had probably just feasted.
"We don't know exactly why this particular group was so big," he said.
While the adult males, with their distinctive 6 feet-tall (2-meter) dorsal fins, were "definitely a showstopper," Pierson said the mothers and their calves were also a big hit.
"You could hear the coos and awws from everyone on board," he said.
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