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A pair of killer whales working in concert have been killing great white sharks along the coast of South Africa since at least 2017, plundering the sharks' nutrient-rich livers and disposing of the rest.
Scientists are trying to understand which hunting approach worked Move it Sharks away From some parts of the coast around Cape Town, and now research has revealed a startling new development in behavior that could provide clues about what this might mean for the wider marine ecosystem.
Scientists witnessed one of the huntersa male orca known as Starboard, single-handedly killed 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 have observed the profound impact that these killer whales are having on the local white shark population,” said Dr. Primo Micarelli, a marine biologist at the Italian Shark Studies Center and the University of Siena, who was on board one of the two vessels that observed them. Researchers through the attack: “Seeing Starboard carrying the liver of a white shark across our ship is unforgettable.”
“Despite my horror for these predators, I am increasingly concerned about the balance of the coastal marine environment,” Micarelli said in a statement.
It is not uncommon for killer whales, which are highly intelligent and social animals, to hunt large animals individually. However, it is the first such incident involving one of the world's largest predators – the great white shark – researchers reported in 2019. Study published on Friday In African Journal of Marine Science.
Lead author Alison Towner, a doctoral researcher at Harvard University, said that killing a starboard contradicts the cooperative hunting behavior widely observed among killer whales, which can surround large prey, such as sea lions, seals and sharks, and use their combined intelligence and strength to attack. Rhodes University.
According to the study, previously observed attacks on great whites involved between two and six killer whales and lasted up to two hours.
“This sighting revealed evidence of solitary hunting by at least one killer whale, challenging traditional cooperative hunting behaviors,” Towner, who has studied great white sharks for 17 years and identified their movement patterns through tagging, said in a recent study. known in the region. statement.
“These are groundbreaking insights into the predatory behavior of this species,” she said. “The presence of these shark-hunting killer whales is probably linked to broader ecosystem dynamics. The rapid developments in this phenomenon make 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 ships were watching the whales. Lethal. .
Less than an hour after arriving, a shark surfaced near the surface, and researchers, tourists and others aboard the ship watched as it grabbed the shark's left pectoral fin and “pushed forward with the shark several times before eventually eviscerating it” in less than two hours. Minutes, the study said.
Later, Starboard was photographed from one of the ships with a “bloody, peach-colored piece of liver” in her mouth, according to the study. Bort, Starboard's male companion, was observed about 100 meters (328 ft) away while the killing was taking place and did not intervene.
Christian Stopforth/Drone Fanatics SA
A second great white shark carcass washed ashore in June near Hartenbos, South Africa.
The duo is a favour Among the study's authors has been involved in hunting and killing great white sharks for many years. Orcas' dorsal fins curve in opposite directions, which is the inspiration for their names.
The two travel long distances along the eastern coast of South Africa to Namibia. Researchers suspect that they first set out on great targeting White in 2015. It wasn't until 2022 that aerial photos were captured for the first time of orcas killing a great white shark, Towner said.
Towner said: “Although we do not have strong evidence on specific motives, the arrival of the pair of killer whales could be linked to broader changes in the ecosystem.” “It is clear that human activities, such as climate change and industrial fishing, are impacting our oceans. To fully understand these dynamics, more research and funding are necessary.
“There are still a lot of unanswered questions about these shark-hunting killer whales and where they come from.”
Orcas are scaring off large numbers of white sharks, but researchers don't know where the sharks are moving to. “As they move, they may end up interfering with heavy commercial fisheries,” Towner added.
The distinct smell of shark liver in the air and seagulls diving towards a spot on the surface of the water, in addition to the carcass of a second shark. The 3.55-metre (11.6 ft) size fish discovered nearby led onlookers to believe another great white may have been killed before boats arrived that day, researchers said.
According to the study, killing by solitary orcas may be possible due to the small size of prey such as the great beluga whale. It has a maximum length of 6.5 meters (21.3 ft) and a mass of 2.5 tons.
The study suggests that the speed of the attack may reflect the starboard's skill and efficiency as a predator, which may be a response to the stress of spending time hunting near beaches in areas where humans are abundant.
“We cannot speculate that this killer whale has become more sophisticated, but the rapid time frame in which the shark was killed shows incredible skill and efficiency,” Towner said via email.
The livers of great white animals are massive organs, accounting for about a third of their body mass. High in fat, killer whales discard the rest of the carcass, a selective feeding behavior known among other carnivores, such as harbor seals, brown bears and wolves, according to the study.
“The observations here add more layers to the fascinating story of these two killer whales and their capabilities,” said Dr. Simon Elwin, founding director and principal scientist at Sea Search Research & Conservation and a researcher at Stellenbosch University in South Africa. a permit.
“As intelligent predators, killer whales can quickly learn new hunting techniques on their own or from others, so observing and understanding the behaviors used here and other killer whales in South Africa is an important part of helping us understand more about these animals,” added Elwin, who was not involved in the study. in search.
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