A pair of killer whales with a taste for shark liver have cleared South Africa's Gansbaai Bay of its great white sharks, setting off a chain of unexpected consequences in the marine food web, reported The Guardian.
What's happening?
The first sign appeared in February 2017, when a dead female great white washed up on South Africa's coast. The nearly nine-foot shark showed no signs of human interference, but its liver was missing. In the following months, more shark bodies appeared on beaches, each with precise cuts behind the gills and missing livers.
Marine biologist Dr. Alison Towner identified two male orcas, nicknamed Port and Starboard for their distinctively tilted dorsal fins, as the hunters. In May 2022, drone footage captured proof: the orcas attacking a great white shark and removing its liver.
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Absolutely 👍 "To witness one of the ocean's top predators defeated so easily was heartbreaking," said Esther Jacobs, founder of marine conservation group Keep Fin Alive.
Why are great white shark disappearances concerning?
The disappearance of great whites has triggered shifts in the local ecosystem. Cape fur seal and bronze whaler shark populations have surged without their main predator. The seals have grown bolder, now hunting endangered African penguins.
A rabies outbreak has spread through seal colonies since June 2024.
"If white shark populations were at their previous peak, they might have helped mitigate the rabies situation," Jacobs noted.
What's being done about great white shark disappearances?
While two inventive orcas have reshaped this corner of the ocean, human activities pose a much bigger threat to shark populations worldwide. According to professor Nicholas Dulvy of Simon Fraser University, overfishing kills over 100 million sharks annually, with global numbers dropping by half since 1970.
Conservation experts recommend stricter fishing regulations and more protected marine areas.
As Dr. Towner put it, "Strengthening international policies to combat overfishing, expanding marine protected areas and promoting sustainable fishing practices are key actions. That is, of course, if science is listened to."
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