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

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.

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.

Killer whales are the only known predators of great white sharks. "They are very selective of the organs that they gain nourishment from and the liver is the most nutritious part of a shark," says Towner. Great white sharks have huge livers which they use as fuel tanks for their lengthy migrations and to maintain their buoyancy. The liver of an adult great white can account for 28% of its body weight, with 90% of its volume coming from high-energy lipids. 

In Australia, orcas have also been observed removing and eating the lips and tongues of baleen whales as well as the pectoral muscle of penguins, says Isabella Reeves, a marine biologist specialising in orcas at the University of Western Australia. This targeted hunting method is "nutritionally driven", she says.

It is difficult to know whether this hunting strategy is a new behaviour or simply being observed more as "there are so many more eyes on the water now" with the rise of underwater cameras and drone technology, says Deborah Giles, an orca scientist at the University of California, Davis, and researcher at the non-profit SeaDoc Society, based on Orcas Island, Washington. "It might simply be that we're looking for it, and we're seeing it." 

The hunting method reveals orcas' "extreme intelligence, and their ability to take advantage of the prey that is available to them within their home ranges", says Giles. "Great white sharks were thought to be the apex predator in the ocean, but it's very clear that it's actually killer whales that are the top predator."

Reeves agrees that orcas "have an edge" over white sharks. "I think it comes down to their culture. They're not lone animals, they live in family-driven societies with clear rules and foundations." 

Great white sharks are primarily solitary animals. Orcas, meanwhile, live and hunt in social groups, known as pods, and use unique vocal "dialects" to communicate with each other. This structure means that orcas are "very coordinated in their hunting strategies", says Towner.

Very occasionally, orcas are spotted hunting by themselves. On 18 June 2023, Starboard was filmed hunting a great white in a solo attack. He killed the juvenile 2.5m (8ft)-long shark and extracted its liver, all in under two minutes. Tourists on a boat filmed the orca with the shark's liver in his mouth, as gulls scavenged the oily liver residue on the sea surface. The next day, a carcass of a second mutilated shark (measuring 3.5m/11.5ft) washed ashore nearby, suggesting that Starboard killed at least two great whites.

"This showed us that Starboard is a highly sophisticated predator… that he doesn't need an accomplice," says Towner.

Erick Higuera, a marine biologist and wildlife filmmaker in Baja California, couldn't believe his eyes when he reviewed a clip from his own drone footage in 2020.

Higuera, who leads the orcas programme at the non-profit Conexiones Terramar and Pelagic Life, had filmed a pod of five orcas preying on a shark in the Gulf of California. "At the time I knew they were hunting a shark, but when I zoomed in months later I realised it was a juvenile great white," he says.

In the footage, the orcas push the great white to the surface before working together to turn it upside down. They then drag the shark underwater and reemerge with its liver in their mouths. "The orcas were ramming the shark and bumping it. Then, they removed the liver and ate it," Higuera says, adding: "They didn't show any signs of eating the carcass, only the liver."

The orcas are members of the "Moctezuma pod", named after a prominent adult male. This pod had already been observed hunting Mobula rays in 2018. But two years later they had moved onto bigger prey: great whites and whale sharks.

In 2022, Higuera filmed five orcas of the Moctezuma pod hunting another juvenile great white. The orcas pushed the shark onto its back and pushed it to the surface. The shark was bleeding and its liver was exposed.

Turning the shark upside down induces a paralysed state known as tonic immobility, says Higuera. "It is essentially a natural, temporary paralysis that occurs when the shark is inverted, rendering it completely inert and unable to react within less than a minute.

"Once the shark has been safely neutralised, the orcas can easily slice open its abdomen to extract and consume the energy-rich liver without risking injury from a dangerous counterattack."

The hunting strategy is a learned behaviour, according to Higuera. "It's a cultural learning in this family, they pass the information along the generations. It comes from the matriarch."

In the Gulf of California, warming waters have increased the presence of juvenile great white sharks, positioning them directly in the habitat of the Moctezuma pod, says Higuera. 

"Climate change is bringing these apex predators into closer proximity, but it is not directly changing how they hunt, [creating] opportunities for orcas to apply their existing, sophisticated hunting strategies to a new target."

This shift may also be happening elsewhere. Orca predation of great whites has also been documented in Australia. In October 2023, the carcass of a 4.7m (15.4ft)-long great white shark washed ashore in southeastern Australia. The shark was missing its liver, digestive and reproductive organs.

"We did the forensics work, as you would for a crime scene, and were able to confirm that there was killer whale DNA in the wounds. It was the first predation confirmed within Australian water," says Reeves, who led the research. Orca predation of great whites has been witnessed elsewhere along the Australian coast but remains rare as there are few areas where the two apex predators happen to aggregate, says Reeves.

The orca attacks may have triggered dramatic changes in great white behaviour in South Africa. The sharks have abruptly fled their previous habitat in the Western Cape and either gone offshore or moved east along the coastline, says Towner. The marine biologist compares it to the behaviour of predators in the Serengeti in Tanzania. 

"Say you have lions introduced to an area where leopards are the top predator, the leopards start to forage more nocturnally to avoid overlapping with the lions in the day," she says. "But the wild dogs do something completely different. They completely move away. We surmise that great white sharks are a lot like wild dogs in their response to another novel apex predator in their space."

South Africa's population of great white sharks was already on the brink before the orca attacks were discovered. A 2016 study spanning six years concluded that South Africa's great whites were "facing extinction" due to poaching for shark jaws and fins, pollution, the depletion of food sources, and the use of shark nets and baited hooks. The species is also suffering from extremely low genetic diversity, according to a 2015 study.

Since then, the population has suffered a further decline, says Sara Andreotti, a marine biologist from Stellenbosch University in South Africa who led both studies. While many are unintentionally killed in fisheries as bycatch, she says, shark nets – which are placed along the coast to keep them away from popular beaches – are the main legal cause of great white fatalities, followed by longline fisheries, which kill smaller juvenile sharks that make up the bulk of the predators' diet.

"We're not giving them a chance to recover, to survive," says Andreotti. "We're seeing them go [locally] extinct before our eyes."

Orca predation is exacerbating the decline, with significant repercussions for the wider marine ecosystem, scientists say.

In False Bay, Cape Town, a relatively stable great white population was documented until 2015. The great whites had completely disappeared from the area by mid-2018, with a study noting that shark-eating orcas likely contributed to the decline.

Off the coast of California, a similar flight pattern has been observed. Brief visits from orcas displaced great white sharks from the Southeast Farallon Island, a shark hotspot located about 27 miles (43km) west of San Francisco, according to a 2019 study analysing long-term electronic tagging data at the site.

The tags showed that the great whites began vacating the area within minutes of the arrival of the orcas. They didn't return to the island until the following season, with knock-on effects for other marine species, such as elephant seals, which great whites usually hunt. The data revealed four to seven fewer predation events on elephant seals in the years white sharks left. 

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By encouraging the displacement of great white sharks from their traditional gathering sites in the Western Cape, orcas are already impacting other species, including critically endangered African penguins which face increased predation from sharks, says Towner.

Meanwhile, another type of shark, the bronze whaler shark, has moved into the territory now that great whites are no longer present, Towner says. These sharks are now the main target species during cage diving, given the absence of great whites in the Western Cape. 

The disappearance of great whites in False Bay, Cape Town, has triggered a ripple effect down the food chain, leading to an increase in their prey, especially Cape fur seals and sevengill sharks, according to a recent study. This in turn has resulted in a decline in smaller sharks and fish.

When orcas displace or kill great white sharks from a part of the coastline, the ecological consequences can be significant, says Towner. "We're now seeing those effects play out in real time."

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