A pod of killer whales hanging out off the California coast has figured out the best ways to hunt their prey in open waters.
With a diet consisting almost entirely of marine mammals, killer whales need to maximize their hunting success to make sure everyone has access to food.
Near the coast, where the species that killer whales feed on can easily be trapped and captured, competition can be fierce. Heading out to sea can provide more food for those who know how to catch it.
The killer whales that make up the transient population of the northeastern Pacific have discovered that seals and whale babies can be hunted with a combination of cunning and brute force. They crush their prey, or toss it into the air with their tails, before settling down to feast.
“The subset of transient killer whales we observed in Monterey Bay stayed preferentially in open, deep waters, feeding primarily on seasonally available California sea lions, gray whale calves, and northern elephant seals.” Write a team led by marine biologist Josh MacInnis From the University of British Columbia in Canada.
“They demonstrated specialized fishing techniques different from those used to catch marine mammals in shallow, near-shore waters associated with coral reefs, rocky outcrops and small islands.”
Worldwide, killer whales are divided into subgroups that are genetically and culturally distinct from each other, known as ecotypes. Three ecotypes They can be found in the northeastern Pacific Ocean – resident, transient and offshore populations.
These groups have their own ways of living the orca life; Although they can be seen in the same general area, they are genetically distinct, have different physical characteristics, pursue different types of prey, and do not interact or mate with each other. They even have it Their orca languages.
Transient killer whales specialize in marine mammals such as seals and other cetaceans, such as dolphins and whales. Because humans live on land, we are able to see how transient killer whales hunt along coastlines quite easily, and their techniques are fairly well documented.
In the late 1980s, scientists off the coast of Canada noticed that some members of the transient group could be found farther afield where inland coastal fishing techniques would not necessarily work. They wanted to know how these outer coastal transients secure a meal.
Their work consists of conducting an analysis of all the information they can get – marine mammal surveys between 2006 and 2018, and whale watching tours between 2014 and 2021 – compiled into a long-term database of killer whale encounters.
Between 2006 and 2021, encounters with populations of killer whales crossing the outer coast have been documented. Their behaviors and group sizes vary seasonally, with the largest overall encounters documented in the spring, when gray whales migrate north from their lagoons around the coast of Mexico.
They have been seen in open waters preying on sea lions, northern elephant seals, dolphins, porpoises, and gray whale calves.
To hunt sea lions, several killer whales would surround a prey animal, taking turns lunging at it and ramming or striking it with their head or tail. They were also throwing the sea lion into the air. Once the sea lion dies, the group divides the animal and eats it or carries it for a while. For elephant seals, the technique is slightly different: killer whales surround the animal, whack it with their tails, then grab it by their flippers to shake it.
Gray whale calf hunts are often initiated and led by adult female killer whales. The group would chase the mother gray whale and her calf until the calf began to tire. The killer whales then separated the calf, getting between it and the mother and grabbing the calf to pull it away. The hunt will become very brutal, with killer whales ramming and biting the calf, and jumping over the blowhole to drown it.
For dolphins, the hunts were highly coordinated, with killer whales surrounding a large school of dolphins to separate individuals. Once a dolphin becomes vulnerable, killer whales push it from below to toss it into the air, or grab it and drag it underwater, until it dies. Similar techniques have been used to hunt porpoises.
The researchers say these findings help us better understand the complexities of the North Pacific ecosystem, and how killer whales fit into different food webs. It also provides us with a context for interpreting the populations and behaviors of orca prey species in which they can be found.
“Transient killer whales have been studied primarily in coastal shallow water habitats, and little information currently exists regarding their behavior in pelagic and deep-sea systems.” They say.
“This study highlights the complex foraging behavior and ecology of transients, how they function as predators in productive deep canyon systems, and how their behavior relates to multiple marine mammal prey populations in the North Pacific Ocean.”
The research was published in One plus.
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