Rare footage of orcas hunting great white shark in SA may explain disappearance

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A drone operator and helicopter pilot captured rare footage of a pod of orcas killing a great white shark near Mossel Bay on the south coast of South Africa. Now sharks haven’t been seen in the area for weeks.

Orca attacks have been cited by scientists as a possible cause of the giant shark species’ disappearance from some waters off the country’s coast.

The footage, captured on the afternoon of May 16, shows a group of five orcas bringing an apparently dead three meter white shark to the surface 400 meters off Hartenbos Beach, according to an October 3 study released by researchers at the Marine Dynamics Academy in Gansbaai, South Africa. Mobile phone footage from a helicopter pilot in the same area at about the same time shows orcas chasing great whites and one of them eating the liver from a dead shark. 

"This behaviour has never been witnessed in detail before, and certainly never from the air," said lead author Alison Towner, a PhD candidate at Rhodes University, South Africa, according to a press release from the Ecological Society of America, which published the study.

Minutes before the attack, white sharks were seen by a number of observers fleeing the area, with some swimming into shallows to escape the orcas.

While 10 sharks were observed during a 75-minute drone flight on the day, only one was seen in daily drone flights over the next eight days, the researchers said. Cage diving operators, who charge tourists to observe sharks from the safety of underwater cages, saw an average of more than three white sharks per trip in the 10 days before the attack and none of the predators for the 45 days after it. 

"Given the well-documented, predictable year-round presence of white sharks in Mossel Bay, the sudden absence of white sharks for several weeks immediately after the predation event supports a flight response by surviving white sharks in the area," the researchers said.

Two orcas, known as Port and Starboard because of their way their dorsal fins lean, have been blamed by a government-appointed panel for the disappearance of white sharks off Cape Town, which lies 344km west of Mossel Bay, after they killed and ate a number of the animals. 

"The study confirmed that one infamous killer whale, locally known as ‘Starboard,’ was part of the pod and ate what was suspected to be a large piece of shark liver at the ocean surface," the Ecological Society said in the statement, referring to the Mossel Bay attack.

In the two years to 2020 only one confirmed sighting of a white shark was recorded in the waters off Cape Town compared with an average of 205 per annum between 2010 and 2016. A similar pattern was observed off California’s Farallon Islands after a spate of orca attacks. 

Earlier this week a dozen white sharks, an unusual number for this time of year, were seen during an aerial survey off the coast of Plettenberg Bay, a popular resort 114km to the east of Mossel Bay, radio Algoa FM reported, citing a statement from the local Bitou Municipality. The municipality said that the sharks may have been "displaced from Mossel Bay" by the orcas.

Plettenberg Bay has reported two fatal attacks on swimmers by white sharks recently, one late last month and the other on June 28. Footage on social media in recent days has shown large sharks swimming in water just a few feet deep off the town’s beaches.

Great white sharks can grow to about five meters and weigh two tons. Orcas can reach eight meters and weigh four tons. 

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