A dozen corpses of disemboweled sharks, stranded on the sand: this is the dismal spectacle discovered at the end of February by scientists alerted by walkers on a beach in the South African region of Cape Town. “Other corpses washed up later in the week. In all, we found 20 sharks, 19 of them flatnose sharks,” said Ralph Watson, 33, marine biologist from Marine Dynamics.
Main suspects: Orcas called Port and Starboard (“Port” and “Starboard”), well known to locals, spotted three days earlier off Gansbaai, a small fishing port 160 kilometers east of Cape Town. This kill is just their latest feat: the duo, recognizable by their twisted dorsal fins, specializes in hunting sharks.
Alison Towner, a shark expert with the Dyer Island Conservation Trust, took part in the autopsies. All of the sharks had characteristic “rake marks” from killer whale bites on their pectoral fins and their livers were “missing,” she said. “This is the first time that killer whales have hunted this species of shark in this specific area,” notes the researcher. But the infernal duo, which has been raging for several years, is notably incriminated in the escape of the great white shark from certain regions off Cape Town.
A “surgical” hunting technique
Port and Starboard arrived near Cape Town in 2015. They first hunt flatnose sharks and then, from 2017, attack great white sharks. Their technique is “surgical”: working as a team, they tear open the chest to gain access to the liver, a “very nutritious, fat-rich” organ, says Ralph Watson.
In October 2022, impressive aerial footage released by scientists showed five of these black and white predators, including Starboard, circling and then gutting a great white shark. This behavior is very unusual. Killer whales normally hunt dolphins in these waters.
According to Simon Elwen, researcher and director of the association Sea Search, the first observations suggest that Port and Starboard “probably come from elsewhere: from West or East Africa, or from the Southern Ocean, We really do not know “.
Unlike their brethren, which stay offshore, the two killer whales are particularly “coastal”. They have been observed “from Namibia to the Port Elizabeth area”, some 800 kilometers east of Cape Town.
The attack filmed in 2022 has scientists worried about the risks of “cultural transmission” between these highly intelligent animals. “This is now an additional threat to shark populations off South African shores,” says Alison Towner.
But the impact of Port and Starboard remains limited. “It’s very shocking to see because suddenly it’s happening on our beaches, but hundreds of thousands of sharks fall victim to fishing every year,” said Ralph Watson. Watching an endangered animal attack another endangered species is “frustrating”, admits Simon Elwen. “But two individual killer whales aren’t going to wipe out a species,” he said.
