After a pair of orcas went on a shark-killing spree in South Africa at the end of February, the internet has been left curious, and harrowed, at the way these killer whales killed their prey.
Each of the 17 massacred sharks had been torn open and was missing its liver. Newsweek spoke to a marine biologist to find out why.
"Different populations of killer whales have specialized diets, such that only a few populations [ecotypes] of killer whales specialize in eating sharks," Andrew Trites, a professor and director of the Marine Mammal Research Unit at the Institute for the Oceans and Fisheries at the University of British Columbia, told Newsweek.
"For example, in British Columbia, we have an ecotype that specializes in eating sharks, while two other local populations specialize in eating either fish or marine mammals."
Despite being called killer whales, orcas are actually large dolphins. They can grow up to 32 feet and weigh up to 6 tons, according to National Geographic. While they eat mostly fish and small marine mammals, some populations of killer whales have developed a taste for sharks.
During February's attack, the orcas—named Port and Starboard— appear to have removed their victims' organs with surgical precision in a heated frenzy for shark foie gras.
In a study published in the African Journal of Marine Science in 2022, marine researchers reported that, since 2017, eight great white shark carcasses had washed up on beaches in the surrounding area, in the Western Cape near Gansbaai. Their bodies bore the tell-tale signs of orca bites, and seven of the eight sharks had also had their livers torn out.
"The reason that killer whales would target the liver of sharks is that it is full of oil and is therefore full of calories, in addition to being big and high in vitamins," Trites said. "It is therefore a great food for killer whales that have a high cost of living and need high caloric food to maintain their energetically expensive lifestyle.
"Sharks have large livers with lots of oil, which helps maintain buoyancy because sharks do not have swim bladders like most fish. The liver accounts for 5 to 10 percent of the weight of a shark, which is extremely high compared to humans and other animals."
Of course, eating sharks does come with its drawbacks—they are apex predators and have evolved tooth-like scales to reduce friction from the water.
"One of the challenges of eating sharks is that their skin is like sandpaper, which means that it wears down the teeth of killer whales that bite into sharks," Trites said.
But eating sharks does not only impact an orca's teeth. It can impact entire ecosystems. Alison Towner, a white shark biologist who has been studying Port and Starboard, previously told Newsweek that great white sharks appear to be keeping their distance from the area, perhaps to avoid reaching the same fate.
"Balance is crucial in marine ecosystems," she said. "For example, with no great white sharks restricting cape fur seal behavior, the seals can predate on critically endangered African penguins, or compete for the small pelagic fish they eat.
"To put it simply, although this is a hypothesis for now, there is only so much pressure an ecosystem can take, and the impacts of orcas removing sharks are likely far wider-reaching."
Correction 03/21/23, 6:43 a.m. ET: This article was updated to correct the spelling of British Columbia.
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Newsweek is committed to challenging conventional wisdom and finding connections in the search for common ground.
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Pandora Dewan is a Senior Science Reporter at Newsweek based in London, UK. Her focus is reporting on science, health ... Read more
