About twenty
disemboweled shark
carcasses , stranded on the sand, have focused scientists on
a duo of killer whales
that for years have wreaked havoc with "surgical" precision on the South African coast.
Ralph Watson, a 33-year-old marine biologist from the Marine Dynamics association, says that at the end of February they found a total of twenty torn to pieces,
nineteen of them flat-nosed
.
The scientists had been alerted by some passers-by.
The main suspects in this slaughter are
the orcas Port and Starboard (Port and Starboard in English)
, well known to the locals, observed three days earlier off the coast of Gansbaai, a small fishing port located 160 km east of Cape Town. .
In July 2022, three killer whales chased, killed and ate the liver of a massive 5m great white shark in South African territorial waters.
The massacre is the latest action carried out by the duo, recognizable by their crooked dorsal fins and specialized in hunting sharks.
Alison Towner, a shark expert with the Dyer Island Conservation Trust, participated in the autopsies.
All of the sharks had "rake marks"
- characteristic of killer whale bites - on their pectoral fins and their livers were "disappeared," she said.
"This is the first time that killer whales have hunted this species of shark in this specific area," says the researcher.
But the infernal duo, which has been raging for several years, is one of the reasons for the escape of the great white shark from certain regions off the coast of Cape Town.
Port and Starboard reached the waters near Cape Town in 2015
.
At first they hunted flatnose sharks, but since 2017 they have also attacked great white sharks.
His technique is "surgical," Watson details.
They work as a team to rip open the chest of their prey and
gain access to the liver, an organ that is "very nutritious and rich in lipids
," he adds.
Photo of an orca.
The attack of Port and Starboard in the coasts near Cape Town terrify the sharks.
Photo: Maxi Jonas / Madryn Tourism
In October 2022, stunning aerial images released by scientists showed five of these black and white predators, including Starboard, circling and disemboweling a great white shark.
This behavior is very unusual.
Orcas normally hunt dolphins in these waters.
According to Simon Elwen, a researcher and director of the Sea Search association, the first observations suggest that Port and Starboard "probably come from other places such as West or East Africa, or even from the Southern Ocean. It is not really known."
Unlike their congeners, which remain offshore, the two orcas are particularly "coastal".
They were seen "from Namibia to the Port Elizabeth region", some 800 km east of Cape Town, it details.
The filmed attack in 2022 worried scientists about the risks of "cultural transmission" between these highly intelligent animals, Elwen adds.
"It's yet another threat to shark populations off the South African coast," Towner says.
But the impact of Port and Starboard remains limited.
"It's very shocking because it happens on our beaches, but
hundreds of thousands of sharks are caught every year
," Watson says.
Watching an endangered animal attack another threatened species is "frustrating", admits Simon Elwen.
"But two individual killer whales are not going to wipe out a species," he sums up.
AFP
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For the first time they film orcas hunting a great white shark: they devour its 250-kilo liver
