A dozen corpses of disemboweled sharks stranded in the sand: that is the grim spectacle discovered by scientists at the end of February of walkers on a beach in the South African region of Cape Town.
“More bodies washed up later in the week. In total we found twenty sharks, including nineteen of the flatnose species,” said Ralph Watson, a 33-year-old marine biologist with Marine Dynamics.
Prime suspects: the orcas Port and Starboard (“Port” and “Starboard” in English), well known to locals, were sighted off Gansbaai, a small fishing port 160km east of Cape Town, three days earlier.
This carnage is just their latest feat: the duo, recognizable by their twisted dorsal fins, specialize in hunting sharks.
Dyer Island Conservation Trust shark expert Alison Towner attended the autopsies. All of the sharks had distinctive “rake marks” from orca bites on their pectoral fins, and their livers were “missing,” she said.
“This is the first time killer whales have hunted this shark species in this specific area,” notes the researcher.
But the hellish duo that has been raging for several years is mainly to blame for the great white shark’s flight from certain regions off Cape Town.
“Surgical” technique
Port and starboard arrive near Cape Town in 2015. They initially hunt flatnose sharks and then attack great white sharks as of 2017.
Their technique is “surgical”: As a team, they tear open the chest to gain access to the liver, an organ that is “very nutritious and rich in lipids,” explains Ralph Watson.
In October 2022, stunning 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 usually hunt dolphins in these waters.
According to Simon Elwen, researcher and director of the Sea Search association, the first observations suggest that port and starboard “probably come from somewhere else: from West or East Africa or even from the Southern Ocean, we really don’t know”.
In contrast to their fellow killers who stay offshore, the two killer whales are particularly “close to the coast”. They have been observed “from Namibia to the Port Elizabeth area”, about 800 km east of Cape Town.
The attack, filmed in 2022, has scientists concerned about the risks of “cultural transmission” between these highly intelligent animals.
“This is now an additional threat to shark populations off the South African coast,” says Alison Towner.
But the port and starboard effects remain limited. “It’s very shocking to see because it’s happening all of a sudden on our beaches, but hundreds of thousands of sharks are killed every year by fishing,” said Ralph Watson.
Watching one endangered animal attack another endangered species is “frustrating”, admits Simon Elwen. “But two individual killer whales will not wipe out a species.”