Liver torn from the body Two orcas drive white sharks out of their territory off South Africa
Ten years ago, hundreds of great white sharks still lived off the coast of South Africa. Now they have largely disappeared. Orcas have recently started to tear out the livers of these notorious predators.
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- Orcas hunt great white sharks off the coast of South Africa.
- The sharks flee and only return in small numbers.
- This has a negative impact on the local ecosystem.
- Following the disappearance of white sharks from the area, the populations of their favorite prey, the Cape fur seal and bronze shark, have risen sharply in Gansbaai.
- Seals in the Western Cape have been infected with rabies since June 2024
Gansbaai, a bay near Cape Town in South Africa, had a population of 800 to 1000 great white sharks around 15 years ago. Adrenaline tourism flourished. However, the predatory fish now avoid this stretch of coast. Because they are hunted - but not by humans.
The first mysterious carcass of a great white shark was washed ashore on February 9, 2017. The 2.6-metre-long body showed no hook or net marks, which ruled out human involvement, as marine biologist Alison Towner explains to theGuardian. Whatever had killed it had disappeared.
Within five days, three more carcasses were found, followed by a fifth in June. For eight eerie weeks, not a single great white shark was sighted. And so it went on: with each death, the sharks in the bay fled for longer periods and returned in smaller numbers.
The torn open carcasses were missing livers
Towner and her colleagues were determined to solve the mystery and carried out autopsies on the four most recently deceased sharks. It turned out that all of them had been torn open with surgical precision at the pectoral girdle, just behind the gills. Two of the bodies were clearly scratched. Most strikingly, all four were missing their livers.
The signs all pointed to the same perpetrators: orcas. Towner's immediate suspects were two male orcas that had been frequent visitors to Gansbaai since 2015. The names given to them by local zoologists were "Port" and "Starboard", named after their distinctive dorsal fins, which had collapsed to the left and right respectively.
The pair had been spotted off the coast of Gansbaai a few hours after the dead sharks were discovered. They were also observed killing sevengill sharks in nearby False Bay and feasting on their livers.
Towner was certain that "Port" and "Starboard" were responsible for the carcasses of the white sharks. "The missing piece of evidence was the direct observation of an attack," she says.
Drone observes orca attack on a great white shark
On 16 May 2022, Christiaan Stopforth was flying his drone over Mossel Bay, about 305 kilometers east of Gansbaai, when he recorded something extraordinary: five orcas attacked a three-meter-long great white shark, biting between its pectoral fins and tearing out its liver. One of the orcas was Starboard.
A helicopter crew witnessed three more kills that day. Just like in Gansbaai, the surviving white sharks from Mossel Bay left the area. None returned for 45 days.
When the orcas Port and Starboard returned to Mossel Bay the following June, Esther Jacobs, founder of the marine conservation organization Keep Fin Alive, was among those who jumped on a boat to watch them. When the team reached the pair, there was the distinct, pungent smell of a shark's liver in the air, indicating a recent kill.
Suddenly, a young great white shark appeared, Jacobs reports, and Starboard attacked it. "It was both awe-inspiring and harrowing. Starboard's tremendous strength was clearly visible as he kept a firm grip on the shark, even as it thrashed around," she recalls. "We watched stunned as he finally gutted the shark." The shark was dead within just two minutes, its liver devoured.
Absence of sharks throws ecosystem out of balance
Today, the great white sharks in Mossel Bay have all but disappeared. Since the incident in 2023, they have not returned in any significant numbers, says Jacobs. "As far as I know, there were less than ten confirmed sightings in 2024."
Following the disappearance of the white sharks from the area, the populations of their favorite prey, the Cape fur seal and bronze shark, have risen sharply in Gansbaai. Ecologists call it a "trophic cascade" when the loss of a predator reverberates down the food chain and throws the ecosystem out of balance.
Marine biologist Towner notes that the seals, which are no longer threatened, "became bolder, some even hunting the endangered African penguins". But: the absence of prey hunters such as sharks can also bring disease. Since June 2024, seals in the Western Cape have been infected with rabies, an epidemic that reached Mossel Bay in July.
"In my opinion, if the great white shark population had been back to its previous peak, it might have helped to mitigate the rabies situation, as rabid seals would probably be easier targets," says Jacobs.
