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Working together, a pair of orcas have been killing great whites off the South African coastline since at least 2017, plundering the sharks’ nutrient-rich livers and discarding the rest.
Scientists are trying to make sense of the hunting approach that is driving sharks away from parts of the coast around Cape Town, and now research has uncovered a surprising new shift in behavior that may offer clues as to what this might mean. wider marine ecosystem.
Scientists witnessed one of the hunters, a male orca known as Starboard, single-handedly kill a 2.5-foot (8.2-meter) juvenile white shark within a two-minute period last year.
“In my annual visits to South Africa for over two decades, I have observed the profound impact these killer whales have on the local white shark population. Marine biologist Dr. of the Italian Shark Research Center and the University of Siena, who was on one of the two ships where the researchers observed the attack. It is unforgettable to see Starboard carrying a white shark liver past our ship,” said Primo Micarelli.
“Despite my fear of these predators, I am increasingly concerned about the balance of coastal marine ecology,” Micarelli said in a statement.
It is not unprecedented for orcas, highly intelligent and social animals, to hunt large animals individually. But this is the first such incident involving the great white shark, one of the world’s top predators, researchers reported in a study published Friday in the African Journal of Marine Science.
Starboard’s killing contrasts with the cooperative hunting behavior more commonly observed 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, PhD. Rhodes University.
Previously observed attacks on great whites occurred between two and six orcas and lasted up to two hours, according to the study.
“This observation revealed evidence that at least one killer whale was hunting alone, challenging traditional cooperative hunting behavior known in the region,” said Towner, who has studied great white sharks for 17 years and learned about their movement patterns through tagging data. expression.
“These are groundbreaking insights into the predatory behavior of this species,” he said. “The existence of these shark-preying killer whales is likely linked to broader ecosystem dynamics. Rapid advances in this phenomenon are making it difficult for science to keep up.”
Port and Starboard
The incident detailed in the investigation took place on June 18, 2023, 800 meters (875 yards) offshore of Seal Island near Mossel Bay, about 400 kilometers (250 miles) east of Cape Town, where people on two vessels observed the orcas. .
Less than an hour after its arrival, a shark appeared near the surface, and researchers, tourists, and others on board witnessed Starboard grasping a shark’s left pectoral fin and “lurching forward several times with the shark before finally eviscerating it” in less than two minutes . minutes, he said, don’t work.
Later, Starboard was photographed from one of the ships with “a piece of peach-colored bloody liver in its mouth,” according to the investigation. Starboard’s boyfriend, Port, was observed approximately 100 meters (328 feet) away while the murder was taking place and was not involved.
The duo are well-known among the study’s authors and have been involved in the hunting and killing of great white sharks for many years. Orcas’ dorsal fins are bent in opposite directions; This inspired their name.
The duo cover great distances along the eastern coastline of South Africa as far as Namibia. Researchers suspect they first began targeting great whites in 2015. Aerial footage of orcas killing great white sharks wasn’t first recorded until 2022, Towner said.
“While we don’t have solid evidence of specific factors, the arrival of the killer whale pair may be linked to broader changes in the ecosystem,” Towner said. “It is clear that human activities such as climate change and industrial fishing are putting our oceans under pressure. Additional research and funding are essential to fully understand these dynamics.
“There are still a lot of unanswered questions about these shark-hunting killer whales and where they come from.”
Killer orcas are terrorizing great white shark populations, but researchers don’t know where the sharks settle. “As they shift, they can overlap with heavy commercial fishing,” Towner added.
The distinct smell of shark liver in the air and seagulls diving toward a slippery surface, along with the carcass of a second 3.55-meter (11.6-foot) shark discovered nearby, led onlookers to believe another great white may have been killed earlier. The boats arrived that day, investigators said.
Killing a lone orca may have been possible if the prey was smaller as a great white juvenile, according to the study. Adult great whites have a maximum length of 6.5 meters (21.3 feet) and a mass of 2.5 tonnes.
The study suggested that the swiftness of the attack may reflect Starboard’s skill and efficiency as a predator, and that it may be a response to the stress of hunting close to the coastline in areas where humans are abundant.
“We can’t imagine this killer whale becoming more sophisticated, but the rapid time period in which it killed the shark shows incredible skill and ingenuity,” Towner said via email.
The livers of great whites are huge organs, about a third of their body mass, and rich in lipids, and orcas discard the rest of the carcass; this is selective feeding behavior known among other carnivores such as harbor seals, brown bears, and wolves. According to research.
Founding director and chief scientist of Sea Search Research & Conservation and researcher at Stellenbosch University in South Africa, Dr. “The sightings reported here add further layers to the fascinating story of these two killer whales and their abilities,” said Simon Elwen. An idiom.
“As intelligent, top predators, killer whales can quickly learn new hunting techniques on their own or from others, so monitoring and understanding the behaviors used by other killer whales here and in South Africa is an important part of helping us learn more about these animals. ” ” added Elwen, who was not involved in the research.
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