Meet the Outer Coast Killer Whales, big game hunters of the deep


There is a mysterious killer whale which prowls deeper waters and specializes in big game hunting, suggests research conducted by a Canadian scientist. West Coast residents are familiar with the iconic and endangered Resident Killer Whales, chinook salmon eaters in the Salish Sea, and the larger Bigg’s Killer Whales, or transient killer whales, which roam the shallower waters of the coast and inlets of British Columbia in search of seals. and other marine mammals.

But growing evidence points to a population of killer whales, known as the Outer Coast Killer Whales, which is a distinct subgroup of transient whales, and which frequents the ocean depths along the continental shelf off the coasts of central California and Oregon, says lead author Josh McInnes. , a scientist in the Marine Mammal Research Unit at the University of British Columbia.

Once believed to be part of the largest population on the West Coast, these Outer Coast Killer Whales have a distinct vocal dialect and culture from their transient cousins, and they specialize in big game hunting, like gray calves and huge elephant seals or sea lions as well as other small cetaceans on the high seas and around the Monterey submarine canyon, McInnes says. “It’s very, very complex and exciting, and we’re just starting to scratch the surface,” he says.

Groups of migrating killer whales move along the Pacific coast, following the prey hunted by their particular populations, from seals to gray whales. Courtesy of Dr Brandon Southall, NMFS / OPR

Identification and catalog 150 members of the Outer Coast population involved combing through over 100,000 images and survey data taken over 13 years by Marine Life Studies, a nonprofit, the National Oceanic and Atmospheric Administration, the Transient Killer Whale Victoria-based Research Project and various whales – watch operations. More individuals are likely to be identified over time as the research continues, McInnes says.

While most of the outer coast killer whales appear to remain in the ocean south of Canada’s border with the United States, 26 members of the group have been sighted in B.C. waters, mixing with groups. coastal passage, McInnes says. The reverse is also true, with sightings of passing whales from British Columbia mingling with inshore group killer whales in the ocean south of the border.

“It’s really exciting because this kind of shows how complex these animals are and we still don’t know enough about their socialization and this bond between (them),” says McInnes.

Outer coastal killer whales may be traveling north to take advantage of the large seal populations in northern waters, he adds, where different whale populations can share their knowledge of other feeding grounds and techniques. of hunting. “We may also see an opportunity for meeting and socializing by spreading genetics between regions,” he says.

The whales of the outer coast specialized in hunting gray whales which migrate north with their mother through California waters in the spring to arctic foraging areas, and again in the fall when they return south to breed in Mexico.

“We think they’re great whale hunters,” McInnes says. “It’s a fascinating event that happens every spring. Orcas congregate in the Monterey Ocean Canyon, especially in April and May, to ambush gray whales.

The hunts, although gruesome, are very dramatic as the orcs take turns hunting gray whales to exhaust the calves, which cannot keep up. Killer whales work to separate the offspring from the adults and repeatedly ram the calves to incapacitate them.

On the beach at Morro Bay in California, the carcass of a gray calf bears the scars indicative of an orca attack.
On the beach at Morro Bay in California, the carcass of a gray calf bears the scars indicative of an orca attack. docentjoyce, CC BY 2.0 / Flickr

If successful, orcas will often feed on a calf for up to two days. Leftovers are not wasted, McInnes says, noting that many marine organisms extract nutrients when the carcass sinks to the ocean floor. He says that when gray whales are absent, the outer coast killer whales primarily feed on California sea lions which can weigh up to 900 pounds and are able to defend themselves.

The groups rely on techniques similar to gray whaling, but they also throw sea lions into the air trying to tire them out and drown them. Orcas also feed on other smaller cetaceans, such as dolphins, porpoises and minke whales, as well as seals.

More research is needed to determine whether the whales of the outer coast are genetically different in any way from the orcas passing further north, and what other dividing lines beyond geography exist between the two. groups.

An orca, or killer whale, makes a breach off the California coast.
An orca, or killer whale, makes a breach off the California coast. Courtesy of Dr Brandon Southall, NMFS / OPR

There is even new evidence to suggest that there may be an additional subtype of orcas that inhabit the depths of the ocean, hundreds of miles offshore, McInnes says, although little is known about it. these “oceanic” killer whales – only 48 have been identified so far. This group of killer whales does not appear to be associated with other passing groups and is most commonly seen up to 200 miles offshore.

Oceanic whales often have a specific type of ocean barnacle on their dorsal fin, and bite marks and scars indicative of a small parasitic shark with razor sharp teeth called the shark cookie cutter, which frequents deep ocean waters far from shore.

These killer whales may form their own population or be part of a community of passing killer whales, McInnes explains, noting that it is difficult to study killer whales given their speed and the distances they travel.

But more research is needed to study all orcas and their possible subgroups, he adds. “Understanding the population dynamics or community structure of a species is so important,” says McInnes. “It helps us put in place specific management plans to protect killer whales, top predators that are very beneficial to marine ecosystems. “


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