Orcas killing sharks off the coast of South Africa

A dozen carcasses of disemboweled sharks washed up on the sand: this grim sight was discovered in late February by scientists, wary passers-by on a beach in the South African region of Cape Town.

“Other carcasses were washed ashore later this week. In total, we found twenty sharks, including nineteen species of flat-noses,” said Ralph Watson, a 33-year-old marine biologist with Marine Dynamics.

The prime suspects are Port and Starboard killer whales, well known to the locals, spotted three days earlier at Gansby, a small fishing port located 160km east of Cape Town.

This massacre is just their latest exploit: the duo, recognizable by their twisted dorsal fins, specialize in hunting sharks.

Alison Towner, a shark expert at the Dyer Island Conservation Foundation, was involved in the autopsy. All the sharks had characteristic “killer whale bite marks” on their pectoral fins and their livers were “missing,” she analyzes.

Sharks off Durban, December 10, 2020 (AFP – Michele Spatari)

“This is the first time killer whales have hunted this species of shark in this particular area,” the researcher notes.

But the infernal duo, which have been raging for several years now, are especially accused of escaping a great white shark from parts of Cape Town.

– “Surgical” technique –

Port and Starboard arrive at Cape Town in 2015. First they prey on flat-nosed sharks, and then, since 2017, they have attacked great white sharks.

Their technique is “surgical”: working as a team, they tear open the chest to gain access to the liver, an organ “very nutritious, rich in lipids,” explains Ralph Watson.

Great white shark off the coast of Gansbaai, March 30, 2010 (AFP - GIANLUIGI GUERCIA)Great white shark off the coast of Gansbaai, March 30, 2010 (AFP – GIANLUIGI GUERCIA)

In October 2022, scientists released spectacular aerial footage of five of these black-and-white predators, including Starboard, circling and then disemboweling a great white shark.

This behavior is very unusual. Killer whales usually hunt dolphins in these waters.

According to Simon Elven, researcher and director of the Sea Search Association, the first sightings suggest that the port and starboard “probably came from somewhere else: from West or East Africa or even from the Southern Ocean, we really don’t know.”

Unlike their relatives, who stay away from the coast, two killer whales live especially “coastal”. They were observed “from Namibia to the Port Elizabeth area”, about 800 km east of Cape Town.

A sign describing the different types of sharks at Gansbai Beach, March 30, 2010 (AFP - GIANLUIGI GUERCIA)A sign describing the different types of sharks at Gansbai Beach, March 30, 2010 (AFP – GIANLUIGI GUERCIA)

The attack, filmed in 2022, has led scientists to worry about the risks of “cultural transmission” between these highly intelligent animals.

“Now this is an additional threat to the shark population on the coast of South Africa,” says Alison Towner.

But the influence of port and starboard remains limited. “It’s very shocking, because all of a sudden it happens on our beaches, but hundreds of thousands of sharks become victims of fishing every year,” says Ralph Watson.

Simon Elven admits that watching endangered animals attack other endangered species is “disappointing”. “But two separate killer whales won’t wipe out the species.”

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