Jorgensen wondered if this was a one-off, but the tags recorded similar examples in later years—orcas arrive, and sharks skedaddle. Some orcas also hunt seals, so it’s possible that the sharks are just trying to avoid competition—but that seems improbable, given how quickly they bolt. The more likely explanation is that the most fearsome shark in the world is terrified of orcas.
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Killer whales have a friendlier image than great white sharks. (Perhaps because of their respective portrayals in movies: Jaws 2 even begins with the beached carcass of a half-eaten orca.) But orcas are “potentially the more dangerous predator,” says Toby Daly-Engel, a shark expert at the Florida Institute of Technology. “They have a lot of social behaviors that sharks do not, which allows them to hunt effectively in groups, communicate among themselves, and teach their young.”
Combining both brains and brawn, orcas have been known to kill sharks in surprisingly complicated ways. Some will drive their prey to the surface and then karate chop them with overhead tail swipes. Others seem to have worked out that they can hold sharks upside-down to induce a paralytic state called tonic immobility. Orcas can kill the fastest species (makos) and the largest (whale sharks). And when they encounter great whites, a few recorded cases suggest that these encounters end very badly for the sharks.
In October 1997, a whale watch vessel near Southeast Farallon Island observed a young white shark swimming towards a pair of orcas that had earlier killed and partly eaten a sea lion. The whales killed the shark, and proceeded to eat its liver. More recently, after orcas passed by a South African beach, five great-white carcasses washed ashore. All were, suspiciously, missing their liver.
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A great white’s liver can account for a quarter of its body weight, and is even richer in fats and oils than whale blubber. It’s “one of the densest sources of calories you can find in the ocean,” Jorgensen says. “The orcas know their business, and they know where that organ lies.”
Rather than ripping their prey apart, it seems that orcas can extract livers with surprising finesse, despite lacking arms and hands. No one has observed their technique, but the wounds on otherwise intact carcasses suggest that they bite their victims near their pectoral fins and then squeeze the liver out through the wounds. “It’s like squeezing toothpaste,” Jorgensen says.
An orca, then, is an apex predator’s apex predator. No wonder sharks flee from them. But orcas don’t actually have to kill any great whites to drive them away. Their mere presence—and most likely their scent—is enough. Many predators have similar effects. Their sounds and smells create a “landscape of fear”—a simmering dread that changes the behavior and whereabouts of their prey. The presence of tiger sharks forces dugongs into deeper waters, where food is scarcer but cover is thicker. The mere sound of dogs can keep raccoons off a beach, changing the community of animals that lives in the tide pools.