For the first time ever, scientists witnessed a lone orca killing a great white shark off the coast of South Africa, further solidifying the mammal's reputation as the ocean's top predator and raising concerns about their impact on the area's ecosystem.

Researchers and tourists in Mossel Bay last June witnessed a killer whale named Starboard hunt an 8-foot great white shark, seizing it by the pectoral fin and "eventually eviscerating it," according to a study published this month in the African Journal of Marine Science. Scientists in a second vessel filmed the episode from a shark-cage submerged in the water and recorded the whale "with a bloody piece of peach-colored liver in its mouth."

Dr. Alison Towner, a shark researcher at Rhodes University in Grahamstown, South Africa, is the lead author of the study. She and her colleagues have been researching interactions between killer whales and sharks in the region for several years.

While researchers have recorded orca whales in the area killing sharks in coordinated group attacks, "predation on a white shark by a lone killer whale has not been documented" before the June 2023 incident, the study says. "All other documented predation by killer whales on sharks in the region has involved 2–6 individuals."

Killer whales can be found in every ocean from the cold waters off Antarctica and Alaska to the coasts of northern South America and Africa, according to the National Oceanic and Atmospheric Administration. They are highly social mammals and spend the vast majority of their lives in groups called pods that can range from a just few whales to more than 20.

Except when they're forced to forage, the apex predators typically hunt in groups and work as a team to catch prey, which is what is notable about the witnessed incident, experts say. Towner, the main author of the study, said in a statement that the sighting was groundbreaking because it challenges conventional hunting behaviors known in the region.

“The astonishing predation ... represents unprecedented behavior underscoring the exceptional proficiency of the killer whale," she said.

The day after scientists witnessed the rare attack, a second white shark carcass washed ashore at Mossell Bay, according to the study. The recent incidents build on previous research that these killer whales predominantly target the livers of white sharks and discard the rest of the carcass.

Josh McInnes, a killer whale researcher at the University of British Columbia, told USA TODAY that the incident shows that killer whales not only are competing with white sharks for seals in the waters off South Africa, but that the mammals can develop niche tastes and independently overpower white sharks.

"This is kind of a rare situation," he said. "We don't see killer whales interacting with other large predators like white sharks very often."

While there still needs to be more research on the subject, McInnes and other experts are concerned that killer whales could drive sharks out of South African water, as they have in other regions.

“The study raises critical questions about the impact of killer whale predation on shark populationsin South Africa,” Towner said. “The displacement of various shark species due to killer whalepresence may have implications for ... changes in the marine ecosystem.”