‘Awe-inspiring and harrowing’: how two orcas with a taste for liver decimated the great white shark capital of the world | Sharks

In the Shadow of Predators: The Disappearance of Great Whites Off South Africa

In the chilly waters off South Africa’s Western Cape, a sinister shift has unfolded. On a crisp February morning in 2017, the first lifeless form of a great white shark washed up on Gansbaai’s shore. No fishing line or hook marks suggested human involvement. What had killed this 2.6-metre-long female remained as elusive as the other great whites that had vanished from the area.

Dr Alison Towner, a Rhodes University marine biologist, noticed the eerie quiet. "We had several sharks acoustically tagged," she recalls, "and later realised three had moved as far as Plettenberg Bay and Algoa Bay, more than 500km east."

Sightings returned to their peak in May, but then, in a grim underscore, three more carcasses were found over five days, followed by a fifth in June. For eight weeks, not a single great white shark was seen. The bay’s population, once 800-1,000 strong, fled for longer and returned in smaller numbers with each killing.

Towner, who had recently begun her doctorate on white shark movement, was left grappling with the surreal reality of her predator turning up dead on the beaches. Necropsies on four recent carcasses revealed that their deaths were connected: all were torn open at the pectoral girdle, two bore distinctive rake marks, and most strikingly, all were missing their livers.

Every sign pointed towards an unlikely culprit: orcas. Two males, dubbed Port and Starboard, were Towner’s immediate suspects. The pair had been spotted off Gansbaai’s coast within hours of each dead shark being discovered.

Drone Footage Captures Rare Orca Attack

Fast-forward to May 2022, and a drone-mounted camera in Mossel Bay captured something extraordinary: five orcas attacking a three-metre-long white shark, biting between its pectoral fins, and tearing out its liver. One of the orcas was Starboard.

Esther Jacobs, founder of the marine conservation charity Keep Fin Alive, witnessed the footage and described the scene as "heartbreaking." She noted, "To witness one of the ocean’s top predators defeated so easily was awe-inspiring and harrowing."

In the aftermath, the surviving white sharks of Mossel Bay also fled, taking 45 days to return. Port and Starboard returned the following June, leaving a pungent scent of shark liver in their wake.

The Ecological Ripple Effect

Today, Mossel Bay’s great white sharks have all but disappeared. Since the 2023 incident, sightings have been scarce. The absence of these apex predators has set off a chain reaction in the ecosystem.

Great white sharks, often considered "doctors of the ocean," usually keep populations of their prey, like cape fur seals and bronze whaler sharks, in check. Without them, populations of these prey species have surged, leading ecologists to warn of a trophic cascade – the unbalancing of ecosystems due to the loss of a predator.

In the absence of sharks, seals have become bolder, encroaching on critically endangered African penguin colonies. Worse still, since June 2024, seals in the Western Cape have become infected with rabies, an epidemic that reached Mossel Bay in July.

The Broader Threat: Human Activities

The drama played out by Port and Starboard is a stark reminder of how ecosystems can rapidly change. Yet, the far greater extinction threat facing all sharks is not these orcas, but humans.

Overfishing, driven by human activities, has resulted in a global extinction of sharks and rays. Studies suggest that global abundance has been halved since 1970, with more than 100 million sharks killed annually and more than a third of species threatened with extinction.

Without effective fishing regulations, the ecological damage seen in South Africa could occur on a much larger scale. "The future of sharks looks bleak if overfishing continues," said Jacobs. Towner echoed the need for strengthening international policies to combat overfishing, expanding marine protected areas, and promoting sustainable fishing practices.

Despite the grim outlook, the future is not set in stone. Science offers a roadmap to preservation, but it’s up to us whether we’ll listen.