Two orcas have apparently developed a taste for the organs of great white sharks off the coast of South Africa, sending the apex predators fleeing from 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 have been killing great white sharks and eating their livers.
Rather than confront the new predators, sharks have fled territories they dominated for years.
Since 2017, eight great white shark carcasses washed up on beaches in the Western Cape, near Gansbaai. Seven of them had their livers removed, and some their hearts as well. Their wounds are distinctively made by the same pair of orcas, researchers said.
Gansbaai, a famous shark-watching spot east of Cape Town, used to attract tourists for activities like cage diving. However, researchers noted, sightings decreased in the years after the orca attacks, and tagging data shows the sharks quickly departing the area.
“Initially, following an Orca attack in Gansbaai, individual Great White Sharks did not appear for weeks or months,” Alison Towner, lead author of the study and a senior white shark biologist, told Science Daily.
“The more the Orcas frequent these sites, the longer the Great White Sharks stay away.”
Prior to these predations on the sharks, there were only two instances since data collection began in Gansbaai when they were absent for a week or more: once in 2007 and again in 2016.
Their longer absence now is disrupting the crucial balance of the ocean ecosystem, Towner said. Without sharks preying on cape fur seals, the seals can go after more critically endangered African penguins or compete for the small fish the penguins eat.
It has also triggered the emergence of a new mid-level predator, the bronze whaler shark, which is known to be eaten by great whites, though the orcas appear to be preying on the bronze whalers, too.
“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,” Towner said.