Two killer whales have apparently developed a taste for the organs of great white sharks off the coast of South Africa, sending the apex predators fleeing a shark-watching hotspot and disrupting the area’s marine ecosystem.
A recent research paper in the African Journal of Marine Science focuses on a pair of killer whales that researchers believe killed white sharks and ate their livers.
Instead of facing the new predators, the sharks have fled the territories they have dominated for years.
Since 2017, eight great white shark carcasses have washed up on beaches in the Western Cape, near Gansbaai. Seven of them had their livers removed, and some had their hearts removed. Their wounds were distinctly made by the same pair of killer whales, the researchers said.
Gansbaai, a famous shark-watching spot east of Cape Town, attracted tourists for activities such as cage diving. However, the researchers note, sightings have decreased in the years since the orca attacks, and tagging data shows that the sharks are rapidly leaving the area.
A great white shark swims in Shark Alley in Gansbaai, South Africa, in 2010.
Ryan Pierce via Getty Images
“Initially, after an orca attack in Gansbaai, individual great whites did not appear for weeks or months,” Alison Towner, lead author of the study and senior white shark biologist, told Science Daily.
“The more killer whales visit these places, the longer the great whites stay away.”
Prior to these predation attacks by the sharks, there had only been two instances since data collection began in Gansbaai where they had been absent for a week or more: once in 2007 and again in 2016.
Their longer absence now upsets the crucial balance of the ocean ecosystem, Towner said. Without sharks preying on fur seals, the seals can hunt more critically endangered African penguins or compete for the small fish the penguins eat.
It also introduced a new mid-level predator, the bronze whaler shark, which is known to be eaten by great whites, although killer whales also appear to prey on bronze whalers.
“Put simply, although it’s a hypothesis at this point, there’s only so much pressure an ecosystem can take, and the impact of killer whales removing sharks is probably much more far-reaching,” Towner said.
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