In the placid turquoise seas off the coast of Mossel Bay in South Africa a vicious power struggle is emerging between two of the world’s deadliest predators.
Killer whales have been captured on camera hunting great white sharks in an hour-long killing spree that culminated in an orca appearing to tear out and eat the liver of its prey.
For several years, great whites have been washing up on the South African coast missing livers and hearts, but this is the first direct evidence that killer whales are responsible.
The drone footage showed five orcas chasing and killing a great white, and experts suspect another three sharks may have been killed in the attack.
One killer whale, known as Starboard, was seen eating what is believed to be a shark liver at the water’s surface.
“This behaviour has never been witnessed in detail before, and certainly never from the air,” said Alison Towner, the study's lead author and a doctoral candidate at Rhodes University, South Africa, who published the findings in the journal Ecology.
Killer whales are actually the largest member of the dolphin family but were originally named "whale killer" by sailors who spotted them hunting whales in large groups.
Experts believe the change in behaviour may be related to a decline in other fish and sharks, forcing the orcas to alter their feeding habits.
The new footage showed how the sharks attempted to evade capture by circling the orca to keep it in view - a common strategy that seals and turtles use to evade sharks.
However, orcas are social and hunt in groups, making the circling strategy ineffective.
“Killer whales are highly intelligent and social animals,” said Dr Simon Elwen, a study co-author, director of Sea Search, and a research associate at Stellenbosch University.
“Their group hunting methods make them incredibly effective predators.”
Great whites have long been the apex predator in the region, and conservationists are concerned that such a dramatic shift at the top of the food chain could unbalance the whole ecosystem.
The sharks are already considered vulnerable because of hunting and are often accidentally caught in fishing nets.
Data from drone footage and whaling boats shows that after the attack in June, sharks in the region fled the Mossel Bay for around six weeks.
Fears for shark populations
There are also fears that the practice will spread to other killer whales. Orcas are known for the ability to pick up new learned behaviours from each other and the report authors are concerned that if it becomes widespread it could have a major impact on shark populations.
Locals have spotted killer whales hunting other kinds of sharks in the area over the past few years but this is the first time they have been proven to be hunting great whites.
David Hurwitz, a whale-watching operator from Simon’s Town Boat Company, said: “We saw them kill a copper shark in 2019 – but this new observation is really something else.”
The new study also analysed drone and cage dive boat survey data before and after the shark attacks and found that although sharks were seen everyday they went missing afterwards.