Battle of the predators: Researchers have filmed for the first time off the coast of South Africa how orcas attack, kill and eat great white sharks. There had been indications of such a hunt by some predatory whales on the large predatory fish before. Now, for the first time, the team has managed to catch the orcas in the act and film them with drones. The recordings show that the killer whales pursue the sharks, circle them and then kill them with one bite. This unusual hunting behavior could be a local and inter-whale trait.
Orcas are social and highly adaptable marine predators. The toothed whales hunt a wide range of prey, ranging from fish, seabirds and cephalopods to sea turtles and other marine mammals including seals and whales. But off the South African coast, some orcas have specialized in a particularly resilient prey: they prefer to hunt great white sharks, as evidenced by orca bite marks on shark carcasses that have been eaten.
Alison Towner from Rhodes University in South Africa and her team have now managed to catch the orcas in the act for the first time. With the help of a drone, they filmed, among other things, how three orcas killed a great white shark in Mossel Bay and pulled it under water. A helicopter pilot filmed another orca attack on sharks. On another occasion, biologists used a drone to observe a whale feeding on a large piece of shark liver shortly after killing a shark.
“This behavior has never been observed in detail before, and never from the air,” says Towner. In one instance, an orca was seen biting into a shark and spinning around, apparently to position the shark so that it would be unable to swim away. Then the killer whale bit its prey in the belly to get to the particularly nutritious liver. “This confirms previous evidence of this strategy in the form of shark carcasses with missing livers and bite marks behind the pectoral fins,” say the biologists.
Footage also reveals the orcas slowly approaching the great whites as they begin to swim in tight circles as an evasive maneuver. As the team explains, this circular swim is a common strategy that sea turtles and seals also use. The animals always keep an eye on the predators during their maneuvers in order to be able to avoid them accordingly.
But this is of little use to the sharks against the social orcas that hunt in groups. “Killer whales are highly intelligent and social animals. Their group hunting methods make them incredibly effective predators,” explains co-author Simon Elwen from Stellenbosch University. Together, the footage and observations provide new insights into how orcas corner, capture and kill great white sharks off South Africa.
Filming of orcas hunting sharks.
At the same time, the new observations demonstrate that hunting of great white sharks among orcas in this coastal area appears to be spreading. After this behavior was previously only known from a pair of male killer whales, mostly hunting together, four other orcas participating in the hunt can now be seen in the videos. The team suspects that the intelligent marine mammals learned this behavior from one another.
“If shark hunting among these orcas is indeed a cultural transmission, then it could have wider implications for the region’s shark populations,” say Towner and her colleagues. (Ecology, 2022; doi:10.1002/ecy.3875)
Quelle: Ecological Society of America
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This article was written by Nadja Podbregar
The original to this post “Battle of the predators: How orcas catch and kill great white sharks” comes from scinexx.
