'What the hell did this?': The orca brothers preying on great white sharks - BBC

When scientists first found dead great whites around South Africa, they couldn't believe their eyes. All bore the same marks of mutilation – their bodies were torn open and their livers had been extracted – and pointed to the same culprit. These deadly tactics are now seen around the world.

On 3 May 2017, a huge carcass of a great white shark washed up on the shore of Gansbaai, a fishing village near Cape Town in South Africa. The female shark weighed 1,100kg (2,425lb) and had a gaping wound on her underside, where her 90kg (198lb) liver had been extracted.

"We were like, 'What the hell did this?'" recalls Alison Towner, who led the necropsy on the dead shark.

In the months that followed, five more great white carcasses turned up. Their bodies all bore the same distinctive scars; they had been torn open and their livers removed.

"It was extraordinary," says Towner, a shark biologist at Rhodes University in Grahamstown, South Africa. "I'd seen hundreds of great white sharks at that point… never had I seen them just wash up one after another, after another."

It was the first sign that an underwater battle was unfolding. As she later learned, it would have ramifications across the world's oceans.

Towner carried out necropsies on all the sharks and when she saw the same pattern of mutilation, she immediately suspected two culprits: a pair of orcas nicknamed Port and Starboard.

These two male orcas, thought to be brothers, were first seen around Cape Town in 2015 and christened Port and Starboard for their distinctive dorsal fins, which collapsed to the left and right.

Shortly after the orca pair were spotted, divers came across a group of dead broadnose sevengill sharks. The stout bodies of these prehistoric-looking sharks were ripped open and missing their livers. "Port and Starboard arrived, right when the divers were pulling the carcasses out of the water," says Towner. "We had the victims and culprits on scene, but at the time we couldn't get our heads around what had happened."

Marine biologists and the public continued to see the two orcas up and down the Cape Town coastline, including around Dyer Island, which used to be known as "the McDonald's drive-through for great whites", due to the sharks that patrolled up and down during the winter months in search of seals, Towner says.

"There was no doubt that Dyer Island was one of the best places on the planet to see a great white," she says. But suddenly the sharks vanished. "I'm not talking about a gradual decline, I'm talking about overnight, gone."

Towner and others had their suspicions, but it wasn't until 2022 that they were able to officially connect orcas with the shark killings. "It was like a crime scene investigation… we were piecing evidence together but we didn't have the silver bullet. Then we got it."

On 16 May 2022, a hobbyist drone pilot filmed three orcas preying on a 3m (10ft)-long great white shark off the coast of Mossel Bay, 400km (250 miles) east of Cape Town. In the encounter, one of the three orcas used its snout to push the shark to the surface and rolled it onto its right side, before biting into an area near its pectoral fins, releasing a pool of blood. The orca then dived underwater with the shark in its mouth, while another orca appeared to grab the shark's tail before disappearing out of sight.

Orcas have now been observed killing great white sharks off the coast of California and Australia too, revealing their remarkable hunting prowess, intelligence and teamwork. With climate change and environmental pressures bringing these species into closer proximity, scientists warn that the battle between the top marine apex predators has dramatic ramifications for life in the ocean.

Battle of the apex predators

Orcas (also known as killer whales) and great white sharks sit at the top of their respective food chains and play an important ecological role in the ocean. They compete for similar prey, such as seals and dolphins.