CAPE TOWN — Marine biologists in Cape Town have confirmed that orcas are hunting great white sharks and removing their livers, a finding that coincides with a sharp decline in the local shark population. Necropsies performed on shark carcasses that washed ashore established that orcas had predated on the great white sharks and extracted their livers.

The coastal waters around Cape Town historically hosted abundant great white sharks. In 2010, tens of thousands of visitors traveled to the city each year for cage diving encounters, with tour operators using blood-chummed water to attract the animals. A few years after 2010, sightings of great white sharks around Cape Town declined and tourist cage diving visits decreased. Sightings have since become rare, and the population of great white sharks around Cape Town has plummeted.

In 2015, divers provided marine biologist Alison Kock with photos showing small shark carcasses on the seafloor with mysterious incisions. Kock initially suspected that humans had made the surgical-looking incisions on the carcasses but later recovered shark bodies and found tooth marks on the pectoral fins, suggesting the carcasses had been attacked by another animal.

While diving in the area where the carcasses had been found, Kock and colleagues encountered two orcas under their boat. The two orcas were observed feeding in the same area where a shark carcass had been recovered. Two years after 2015 — in 2017 — great white shark carcasses began washing ashore with their livers removed. Before these incidents, no one in Cape Town had observed orcas killing great white sharks, though orcas had been present in the waters for years. About ten years ago, carcasses had also begun washing up on nearby beaches with their livers missing. A great white shark's liver is the most calorie-dense organ in its body and constitutes nearly one third of its body mass.

Cape Town-based whale-watching tour operator David Hurwitz observed two male orcas hunting and killing great white sharks near the city. Hurwitz named the pair Port and Starboard because their dorsal fins had collapsed, one to the left and one to the right. The two orcas hunted great white sharks in pairs, unlike most orcas, which hunt in larger groups called pods. Scientists believe Port and Starboard may be teaching other orcas to hunt great white sharks. In 2022, drone footage captured five orcas working together to stun and kill a great white shark off the coast of South Africa.

Photographer and naturalist Chris Fallows had observed between 250 and 300 individual great white sharks per year before their numbers declined. Kock has maintained that the presence of orcas has displaced great white sharks further along the coast of South Africa, while asserting that the overall population of great white sharks in South African waters is stable. Orcas are also known to hunt great white sharks off the coast of California and around Australia. Enrico Gennari said that interactions between orcas and great white sharks similar to those in South Africa have occurred in California and Australia.