In early 2022, a group of killer whales were observed by a team of researchers in South Africa hunting great white sharks ( Carcharodon carcharias ). Quite a milestone. It was the first time that this hunting behavior towards a white shark had been observed in killer whales. Now, new footage of the chase reveals that more orcas are involved than previously thought. Specifically, the video shows five killer whales participating in the event, leading scientists to suspect that the behavior could be spreading through cultural transmission.
a bloodbath
In the video, recorded by drones and helicopters in the southern province of Western Cape, a pod of killer whales ( Orcinus orca ) are seen on camera killing one of the world’s largest marine predators: the great white shark.
“This behavior has never been seen in detail before, and certainly never from the air,” said Alison Towner, a shark scientist at the Academy of Marine Dynamics in Gansbaai, South Africa, and lead author of the study published in the journal Ecology.
While a short video of the drone footage was broadcast in June, this was only part of an hour-long hunt for multiple sharks, as exclusive helicopter footage reveals, and the new document offers longer footage, along with new data showing that white sharks fled the Mossel Bay region of South Africa for several weeks because of this ‘shark hunt’.
Only two killer whales in South Africa had previously been linked to hunting white sharks, but they had never been seen in action. The authors believe that the involvement of these four new whales suggests that the behavior may be spreading.
“Sharks eventually abandoned key former habitats, which has had significant knock-on effects for both the ecosystem and shark-related tourism,” she says.
Orcas, top predators in the ocean
Scientists at the Academy of Marine Dynamics, who studied the videos and wrote this study, determined that a total of 10 sharks were observed on May 16 when killer whales attacked the sharks.
“Given the predictable and well-documented year-round presence of white sharks in Mossel Bay, the sudden absence of white sharks for several weeks immediately following the predation event supports a response to surviving great white sharks in the area.” the authors.
According to the study authors, a single adult great white shark liver roughly meets the daily energy demands of a full-size male killer whale, so it ‘s telling that shark carcasses have been found with bite marks around the pectoral fins and missing livers.
“Killer whales are highly intelligent and social animals” . Their group hunting methods make them incredibly effective predators,” says co-author Simon Elwen .
The authors suggest that if more killer whales adopt the practice of hunting white sharks, then the behavior will have a much greater impact on shark populations. The number of sharks in the open sea has been reduced by more than 70 percent in just 50 years . The great white shark is in a vulnerable state, according to the International Union for Conservation of Nature (IUCN).
Referencia: Alison V. Towner et al, Direct observation of killer whales predating on white sharks and evidence of a flight response, Ecology (2022). DOI: 10.1002/ecy.3875
