shark liver killer whale
Facebook / Marine Dynamics

Killer whales are believed to be responsible for slaying several huge great white sharks off the coast of South Africa and removing their livers with "surgical precision".

Scientists from the Western Cape believe orcas are killing the sharks to feast on their vitamin rich livers. Such a behaviour would be almost unprecedented in South Africa.

On Sunday (7 May) a great white washed up on the coast of Struisbaai – at least the third to have surfaced with its liver apparently harvested near the town of Gansbaai in recent months .

"We have never seen anything like this. Today's carcass is another large white shark, he is a 4.2m male and his injuries seem to match those of the previous two dead specimens.

"It seems likely that orcas are again the cause of death but we will confirm after the autopsy," said Alison Towner, a biologist at the Dyer Island Conservation Trust, in a Facebook post.

Just days earlier on 3 May, a 4.9m female was found liver-less on the beach at Franskraal. Another turned up in the same destination on 8 February.

These three findings have been confirmed by Towner and other marine biologists from the Dyer Island Conservation Trust. A further two similar sightings have been reported nearby but not seen by the group.

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Sharks' livers are rich in squalene, an organic compound vital to synthesising cholesterol, steroid hormones, and vitamin D. It is not unknown for orcas to feast on shark organs but the behaviour had previously been rare near the Western Cape.

The string of deaths have also coincided with a notable absence of sharks in the waters around Gansbaai – a town that relies heavily on tourism from shark watchers. The presence of orcas is believed to be driving the shark's away.

Marine Dynamics, a local shark cage diving company, said one of their vessels had returned from an expedition without a single shark sighting on 7 May – the day of the most recent sighting.

"Obviously this is a very sad time for us all, nature can be so cruel and the dexterity these enormous animals are capable of is mind blowing, almost surgical precision as they remove the squalene rich liver of the white sharks and dump their carcass," Towner said.