A pair of orcas working in concert have been killing great whites along a stretch of South African coastline since at least 2017, plundering the sharks’ nutrient-rich livers and discarding the rest.
Scientists have been trying to make sense of the hunting approach, which has driven the sharks away from some parts of the coast around Cape Town, and now research has revealed a startling new twist in the behavior that could offer clues on what it might mean for the wider marine ecosystem.
Scientists witnessed one of the hunters, a male orca known as Starboard, single-handedly kill a 2.5-meter (8.2-foot) juvenile white shark within a two-minute time frame last year.
“Over two decades of annual visits to South Africa, I’ve observed the profound impact these killer whales have on the local white shark population. Seeing Starboard carry a white shark’s liver past our vessel is unforgettable,” said Dr. Primo Micarelli, a marine biologist at Italy’s Sharks Studies Centre and the University of Siena who was aboard one of two vessels from which researchers observed the attack.
“Despite my awe for these predators, I’m increasingly concerned about the coastal marine ecology balance,” Micarelli said in a statement.
It’s not unprecedented for orcas, highly intelligent and social animals, to hunt large animals individually. However, it’s the first such occurrence involving what is one of the world’s largest predators — the great white shark — the researchers reported in a study published Friday in the African Journal of Marine Science.
Starboard’s kill is at odds with more widely observed cooperative hunting behavior among orcas, which can surround large prey, such as sea lions, seals and sharks, and use their combined intelligence and strength to attack, said lead author Alison Towner, a doctoral researcher at Rhodes University.
The killer orcas are scaring off great white shark populations, but researchers don’t know where the sharks are relocating. “As they relocate, they might end up overlapping with heavy commercial fisheries,” Towner added.
Yes, but it’s a little unusual that one orca was hunting alone, and the shark was a large juvenile. The scientists think that the ecological mess that has resulted in the killer whales pushing out all but the boldest teenager great white sharks could mean that the sharks are going somewhere else, possibly where humans fish or swim or where the local wildlife is not ready for the sharks.