Orca that hunt great whites "literally tear the shark apart" by each grabbing hold of a pectoral fin, the owner of a whale watching company who has been following these predators for several years told Newsweek.
David Hurwitz of whale watching group Simon's Boat Company in South Africa, said two orca spotted on January 16 are known to hunt great white sharks. The pair, named Port and Starboard after the direction of their collapsed dorsal fins, were seen in the False Bay area off the Western Cape of South Africa.
The history of the pair's presence off the Western Cape extends back to 2009. Yet their story as shark hunters commenced several years later, amid strange discoveries made in 2014.
"Carcasses of seven-gill [and] cow sharks were being discovered by local divers. They all had long surgical-type incisions on their ventral side, between their pectoral fins, through which their livers had been removed," Hurwitz said.
"Initially this was attributed to fishermen who were possibly taking the livers to use as bait. However, what was also of great concern to the divers was that all the remaining cow sharks had deserted the area."
As Hurwitz and scientists in the False Bay area began to examine the orca behavior and their impact on sharks in the area, a link was made between their presence and the number of shark carcasses washing ashore with these reoccurring injuries.
It is now thought that Port and Starboard deliberately target sharks for their livers as a form of special delicacy. "On each visit they would follow a similar inshore route around the bay through high density shark areas and it became obvious what they were after," Hurwitz said. "Fresh shark carcasses and photographic records of the previous necropsies were examined by Dr Alison Kock and distinct killer whale tooth impressions were noted on their pectoral fins.
"The shark mystery was answered! The technique the killer whales employed was for each to grab onto a pectoral fin and literally tear the shark apart, in order to remove the squalene-rich livers—the shark's largest and most nutritious organ," he said.
Initially, the orca targeted smaller species of shark like seven-gills. However, in 2017 they appeared to have move onto larger prey—great white sharks.
"Over the course of 2017, five great white sharks washed ashore in the Gansbaai area with similar trauma to the cow sharks found in False Bay. Dr Ali Towner who conducted the necropsies came to the same conclusion as her colleague in Cape Town—killer whales!" Hurwitz said.
Shark numbers in False Bay have fallen dramatically since orca started hunting them. Before 2017, hundreds would visit the bay every year. In 2021, there were just a handful of sightings.
Port and Starboard's shark-hunting caused a stir beyond the False Bay area. Declining numbers of white sharks off the Western Cape was linked with the presence of orca and their ability to hunt the animals and so deter them from frequenting the area.
The situation even prompted the involvement of the South African government. A report published by the Department of Environment, Forestry and Fisheries in October 2020 detailed the declining numbers of great white sharks in the areas and linking it in part to the presence of orca.
"The sudden decrease in white shark numbers has been noted as a major concern ... The Panel found some evidence for a causative link between the appearances of a pod of orcas that had specialised on preying on white sharks," one section of the report said.
The January 16 sighting of Port and Starboard is the latest in an ongoing saga that has impacted marine ecosystems in the area and proved a boon for whale watchers like Hurwitz, who have witnessed the incidents unfold in front of them.
"So for as long as Port and Starboard keep coming to False Bay, I don't see this situation changing, in fact its increasing; since 2017 they have been sighted here a further 33 times," he said. "As a whale watching tour operator, this has been a bonanza and I've had the great privilege to have observed them dozens of times and spent 100's of hours with them."
