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Since at least 2017, two killer whales have been working together to kill great white sharks along South Africa's coast, plundering the shark's nutritious liver and discarding the rest.
Scientists have been trying to understand this hunting technique that drove sharks away from parts of the coast around Cape Town, but the new study reveals a surprising new twist in shark behavior. This could provide clues as to what this means for sharks. wider marine ecosystem.
Last year, scientists witnessed one of the hunters, a male orca known as Starboard, single-handedly kill a 2.5-meter (8.2-foot) juvenile great white shark within two minutes.
“I have visited South Africa every year for over 20 years and have observed the huge impact that killer whales have on the local great white shark population. It was an unforgettable sight to see,” said Dr. Primo Miccarelli, a marine biologist at Italy's Shark Research Center and the University of Siena, who was on board one of the two vessels where researchers observed the attack. .
“Despite my awe for these predators, I am increasingly concerned about the balance of coastal marine ecosystems,” Miccarelli said in a statement.
As highly intelligent and social animals, it is not unheard of for killer whales to hunt large animals individually. But this is the first such incident involving the great white shark, one of the world's largest predators, researchers report in a study published Friday in the African Journal of Marine Science.
Starboard's capture is inconsistent with the widely observed cooperative hunting behavior among killer whales, which can surround large prey such as sea lions, seals, and sharks and attack them using intelligence and combined force. said lead author and doctoral researcher Alison Towner. Rhodes University.
Previously observed attacks on great white sharks have involved two to six killer whales and lasted up to two hours, according to the study.
“This sighting reveals evidence that at least one killer whale was hunting alone, calling into question the traditional cooperative hunting behavior known in this region.” Towner, who has been researching and learning about their behavioral patterns through tagging data, wrote in his paper. statement.
“These are groundbreaking insights into the predatory behavior of this species,” she says. “The presence of these shark-hunting killer whales may be related to broader ecosystem dynamics. The rapid development of this phenomenon is making it difficult 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 boats were observing orcas. .
Within an hour of their arrival, the shark appeared near the surface, and researchers, tourists, and others on board the ship noticed that Starboard grabbed the shark's left pectoral fin and within two hours, the shark appeared near the surface. “After lunging forward with the shark several times, he finally eviscerated it.” Just a few minutes, the study said.
The starboard vessel was then photographed from one of the vessels with a “bloody pink piece of liver in its mouth,” according to the study. Starboard's male companion, Port, was observed approximately 100 meters (328 ft) away while the killing was taking place and was not involved.
Christian Stopforth/Drone Fanatics SA
A second great white shark carcass washed ashore near Hartenbosch, South Africa, in June.
The two men are well known among authors of research papers and have been involved in hunting and killing great white sharks for many years. Killer whales' dorsal fins curve in opposite directions, which is where their name comes from.
The two travel the long distance along the east coast of South Africa to Namibia. Researchers suspect they first started targeting the greats. White people in 2015. The first time an orca was captured on aerial footage killing a great white shark was in 2022, Towner said.
“Although we don't have hard evidence about specific factors, the appearance of killer whale pairs may be related to broader changes in the ecosystem,” Towner said. “It is clear that climate change and human activities such as fishing are stressing the oceans. Additional research and funding is essential to fully understand these dynamics.
“There are still many unanswered questions about shark-hunting killer whales and where they come from.”
Killer killer whales are driving away great white shark populations, but researchers don't know where the sharks are moving. “If they relocate, they could eventually overlap with large-scale commercial fishing,” Towner added.
The distinct smell of shark liver wafts through the air, a seagull dives into the film on the water's surface, and a second shark carcass. Researchers said a 3.55-meter (11.6-foot) great white shark was spotted nearby, leading onlookers to believe another great white shark might have been killed before the boat arrived that day.
The kill by a single killer whale may have been possible because the prey was small, a juvenile great white, the study said. Adult great white sharks can grow up to 6.5 meters (21.3 feet) long and weigh 2.5 tons.
The quickness of the attack may reflect the starboard's skill and efficiency as a predator, and may be a response to the stress of spending time hunting near coastlines in human-populated areas. Research suggested that there is.
“While we cannot infer that this killer whale is more sophisticated, the short time he took down sharks shows incredible skill and proficiency,” Towner said in an email. .
A great white shark's liver is a huge organ, making up about one-third of the shark's body weight. Rich in lipids, killer whales discard the remaining carcasses. Research shows this is a selective feeding behavior known among other carnivores, including harbor seals, brown bears, and wolves.
“The observations reported here add another layer to the fascinating story of these two killer whales and their capabilities,” said Dr. Dr Simon Elwen, also a researcher at the university, said: statement.
“As smart apex predators, killer whales can quickly learn new hunting techniques on their own or from other killer whales. That's why it's important to monitor and understand the behaviors used by other killer whales here and in South Africa. “This is an important part of understanding more about these animals,” added Erwen, who was not involved in the study.
