This Could Be Why Orcas Have Been Eating Great White Sharks in South Africa

A South African shark-watching hotspot has recently turned into the scene of a seaside horror movie. For several months, enormous great white shark corpses have been washing up on the Gansbaai beaches, often missing their livers as if feasted upon by cetacean Hannibal Lecters. But this is no movie—it’s just biology, ruthless as ever.

This week is Shark Week  (SharkFest?), when networks like the Discovery Channel and Nat Geo Wild air (often pseudoscientific) shark-related programming to the shark-hungry public. While Shark Week programming is notorious for feeding into our fears about sharks, it turns out these fish are rarely a match for the orca whales. If we’re trying to celebrate a food chain-topping marine animal, it might be time for an Orca Week instead.

“Those that say sharks are apex predators, that’s not the case,” George Burgess, Director of the International Shark Attack File at the Florida Museum of Natural History told Gizmodo. “As hard as it is to say it, the killer whales are a step above.”

After Gansbaai’s first incident just a few months ago, a handful of liverless great white shark carcasses have washed up on the South African beach in just a few months. The missing livers point to possible orca attacks—as we’ve reported before, shark livers are full of the nutrient squalene, which the orcas seem to be after.

The attacks might be new in South Africa, but certainly aren’t out of the ordinary for killer whales, said professor Rus Hoelzel from Durham University in the UK. “Killer whales can eat pretty much anything—they’re very good predators,” he said. “Working in a group certainly helps.” (Great white sharks can hunt in groups as well, but have a reputation for being lone hunters.)

Hoelzel noted that some orca whales have been spotted only eating specific animals, like dolphins. But scientists have found others with both dolphin meat and fish meat in their bellies. Folks have spotted orcas killing dolphins and sea lions, and a Nat Geo documentary shows whales eating a great white in 1997. Finally, back in late 2016, drones took this nightmarish footage of orca whales wrecking a shark:

The real question, then, isn’t whether orcas eat sharks (they do), but what’s changed in Gansbaai to amp up the number of attacks. Representatives from Marine Dynamics who’ve blogged about the recent events declined to comment for this story. But Burgess had some ideas

“We do know that there has been a rise in white shark populations in certain areas of the world, such as on both coasts of the United States thanks to proper fishery management and endangered species status given to the white shark’s primary food items,” he said.

Basically, better shark management could have led to rising populations. Killer whales, too, are protected. “It may be that there are some modifications in their ranges,” said Burgess. “The animals may also be coming together more often, perhaps as a result of local environmental conditions.” We may be witnessing something that’s always happened, but better conservation practices or environmental changes are making it more common.

As for what induces the individual attacks, there are lots of reasons a great white would approach a pod of orcas. Great whites spend a lot of time chasing their next meal, and usually win their encounters with other animals, so why not attack an orca? Little do they know, orca whales can lay them out with a headbutt to the vulnerable belly full of nutritious organ meat, said Burgess. Which the whales might not actually eat, mind you.

“It comes down to whether the killer whales are going after the shark at their vulnerable spot to disable them and eat an important part of them, or if they’re there to essentially play with something that they’ve defeated, a la the cat,” said Burgess.

Orcas, it turns out, can be truly brutal. So, Discovery Channel, when are we getting our Orca Week?

source: by Ryan F. Mandelbaum

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