by Sign up for CNN’s Wonder Theory science newsletter. Explore the universe with news on exciting discoveries, scientific advances and more.
A pair of orcas working in concert have been killing great whites along a stretch of the South African coast since at least 2017, ravaging the sharks’ nutrient-rich livers and scavenging the rest.
Scientists are trying to make sense of the hunting approach, which has driven the sharks away from certain parts of the coast around Cape Town, and now research has revealed a surprising new twist in behavior that could provide clues as to what ‘could mean. the wider marine ecosystem.
Scientists witnessed one of the hunters, a male orca known as Starboard, being single-handedly killed by a 2.5-meter (8.2-foot) juvenile white shark within a two-minute time frame last year.
“Over twenty years of annual visits to South Africa, I have observed the profound impact these killer whales have on the local white shark population. It is impossible to forget to see the Starboard carrying the liver of the great white shark over our vessel,” said Dr. Primo Micarelli, a marine biologist at the Italian Center for Shark Studies and the University of Siena who was on board one of two vessels from which researchers observed the attack.
“Despite my admiration for these predators, I am more concerned about the balance of the coastal marine ecology,” Micarelli said in a statement.
It is not unprecedented for orcas, very intelligent and social animals, to hunt large animals alone. However, it is the first such incident involving one of the world’s largest predators – the great white shark – that the researchers reported in a study published on Friday in the African Journal of Marine Science.
The Killing of the Plantain is at odds with cooperative hunting behavior more widely observed among orcas, which can surround large prey, such as sea lions, seals and sharks, and use their combined knowledge and strength to attack, said lead author Alison Towner, a doctoral researcher at Rhodes University.
Previous observed attacks on great whites involved between two and six orcas and took up to two hours, according to the study.
“This sighting showed evidence of solitary hunting by at least one killer whale, defying cooperative hunting behaviors known in the region,” said Towner, who has studied great white sharks for 17 years, at learn about their movement patterns through tagging data, in a. statement.
“These are ground-breaking insights into the predatory behavior of this species,” she said. “Perhaps the presence of these killer whales hunting sharks is related to wider ecosystem dynamics. Due to rapid developments in this phenomenon, it is challenging for science to keep up.”
Port and Starboard
The event detailed in the study occurred on June 18, 2023, 800 meters (875 yards) offshore near Seal Island near Mossel Bay – about 400 kilometers (250 miles) east of Cape Town – where people on two ships watching the orcas. .
Less than an hour after its arrival, a shark came close to the surface, and researchers, tourists and others on board the Starboard saw it grab the shark’s left pectoral fin and “thrust the shark forward several times before He dispossessed” in less than two. minutes, the study said.
Starboard was later photographed from one of the vessels with a “bloody piece of peach-colored liver in his mouth,” according to the study. A male Starboard mate, Port, was seen about 100 meters (328 feet) away as the killing took place and was not involved.
The duo is well-known among the authors of the study and has been involved in the hunting and killing of great white sharks for many years. The orcas’ dorsal fins are bent in opposite directions — the inspiration for their name.
Both travel great distances along the east coast of South Africa up to as far as Namibia. Researchers suspect they began targeting great whites in 2015. It wasn’t until 2022 that aerial footage first captured the orcas being killed by a great white shark, Towner said.
“While we don’t have firm evidence of the specific drivers, the arrival of the pair of killer whales could be linked to broader changes in the ecosystem,” Towner said. “Human activities, such as climate change and industrial fishing, are clearly stressing our oceans. To fully understand these dynamics, additional research and funding is necessary.
“There are still many unanswered questions about these killer whales that hunted sharks and where they came from.”
The deadly orcas are terrorizing a large population of great white sharks, but researchers don’t know where the sharks are relocating. “As they relocate, they may overlap with heavy commercial fisheries,” Towner said.
The distinctive smell of shark liver in the air and seagulls diving towards a slick on the water’s surface, as well as a second 3.55 meter (11.6 ft) shark carcass found nearby, led onlookers to believe it may have been killed another great white before death. the arrival of the boats that day, the researchers said.
The kill by a single orca may have been possible due to the smaller size of the prey as a juvenile great white, according to the study. Adult large bays have a maximum length of 6.5 meters (21.3 feet) and a mass of 2.5 tonnes.
The speed of the attack may reflect Starboard’s skill and efficiency as a predator, which may be a response to the stress of spending time hunting close to shore in densely populated areas, the study suggested.
“We cannot speculate that this killer whale has become more sophisticated but the rapid time frame in which it killed the shark shows incredible skill and competence,” Towner said via email.
The livers of great whites are huge organs, about a third of their body mass, and rich in lipids, while orcas scavenge the rest of the carcass – a selective feeding behavior known among other carnivores, such as harbor seals, brown bears and a wolf. , according to the study.
“The observations reported here add more layers to the amazing story of these two killer whales and their abilities,” said Dr. Simon Elwen, founding director and chief scientist at Sea Search Research & Conservation and researcher at Stellenbosch University in South Africa, i. statement.
“As top predators, killer whales can quickly learn new hunting techniques on their own or from others, so monitoring and understanding the behaviors used here and by other killer whales in the South Africa to help us understand more about these animals. ,” said Elwen, who was not involved in the research.
For more CNN news and newsletters create an account at CNN.com
