Many believe that the top predator in the ocean is the great white shark (Carcharodon carcharias). But the recent disappearance of these massive sharks off South Africa shows that contrary to belief, it is not the ocean’s top apex predator… that title belongs to orcas (Orcinus orca). Also known as killer whales, they’re the largest of the dolphins and one of the world’s most powerful predators. Previous research has shown that when killer whales entered the scene, great white sharks make an exit – and many times did not return for months.
It’s even worse when the sharks are hunted down by the black-and-white marine mammals.
Yup, you read that correctly! Aerial footage earlier this year was shared on Discovery Channel’s Shark Week, showing a predatory chase rocked the internet. “While a clip of the drone footage was aired in June, this was only part of an hour-long hunt of multiple sharks, as revealed by the exclusive helicopter footage, and the new paper offers more extensive footage, along with data from tags, drone surveys and shark-tour boats showing that white sharks fled from the Mossel Bay region of South Africa for several weeks,” says Alison Towner, a senior shark scientist at Marine Dynamics Academy in Gansbaai, South Africa. You can see the footage here. This new paper is the third data chapter of her doctoral thesis and provides novel insights into how orcas chased, captured, and killed white sharks. “This helicopter footage revealed that this hunt lasted for over an hour and gave evidence of possible cultural transmission (adult to adult learning) as other individuals participated alongside the well-known shark eater ‘Starboard’,” said Towner on a Facebook post.
A highly social animal that hunts in coordinated packs, orca hunting techniques vary from region to region depending on available food items. While the rows of razor-sharp teeth can pierce even the thickest whale hide, orcas make quick work of the sharks by flipping them over. This causes them to go into “tonic immobility,” a natural state of paralysis that animals enter. Often called animal hypnosis, its function isn’t exactly understood. However, the orcas take advantage of this reflex and temporary state of inactivity, making for an easy meal.
Only two killer whales in South Africa have been previously linked to hunting white sharks, Port and Starboard, even though no one had seen them ‘in action.’ The pair of adult male orcas frequent the country’s coastline, making their first known kill back in 2015. “I first saw Starboard in 2015 when he and his close-associated ‘Port’ were linked to killing seven gill sharks in False Bay. We saw them kill a bronze whaler [copper shark] in 2019 – but this new observation is really something else,” said David Hurwitz, a boat-based whale-watching operator from Simon’s Town Boat Company. Only Starboard was observed in this new footage, along with four other killer whales. The authors believe that the involvement of these four new whales suggests the behavior may be spreading. The footage showed Starboard eating what was suspected to be a large piece of shark liver at the ocean surface, with another currently un-identified killer whale biting into a white shark at the region of the liver.
Previous studies have documented how new behaviors spread among killer whales over time through cultural transmission. Culture, defined as shared behavior or information within a community acquired through social learning, is not exclusively human. In fact, it has been discovered that orcas have evolved their own complex culture through a suite of behaviors, shaping what and how they eat, their choice of mates, and even how they spend their free, “fun” time. There are a variety of complex, learned behaviors found among pods that differ from one another, such as hunting, for example. “Killer whales are highly intelligent and social animals. Their group hunting methods make them incredibly effective predators,” said marine mammal specialist and study co-author Dr Simon Elwen, Director of Sea Search and a research associate at Stellenbosch University. The authors suggest that if more killer whales adopt the practice of hunting white sharks, then the behavior will have far wider impacts on shark populations.
Now this all makes it seem like the sharks aren’t putting up a fight – trust us, they are. They just aren’t a match for a killer whale’s hunting strategy. The new footage shows this great white shark attempted to evade capture by orcas, using behavior not previously seen exhibited by these large predators. “On two occasions, orcas approached sharks closely and slowly, while the shark, instead of fleeing, stayed close to the orca, keeping it in view – a common strategy that seals and turtles use to evade sharks. However, orcas are social and hunt in groups, and the researchers believe these behaviors may render the circling strategy ineffective for white sharks,” explained a press release.
Once a shark (or multiple) are killed, many times others disappear lest they want to become a quick meal. Towner and her co-authors analyzed drone footage and cage dive boat survey data before and after these most recent predation events. “White sharks were seen on every survey day for the weeks prior to the predation event and multiple sharks were seen on the day of the predations. However, only a single white shark was seen in the 45 days after the predations, confirming a flight response by sharks,” the team said. This pattern has been happening since the first attacks back in 2015. South African National Parks’ shark expert and marine biologist, Dr. Alison Kock, explained further: “We first observed the flight responses of seven gills and white sharks to the presence of killer whales Port and Starboard in False Bay in 2015 and 2017. The sharks ultimately abandoned former key habitats, which has had significant knock-on effects for both the ecosystem and shark-related tourism.” It’s not only here that is suffering, with orcas scaring off great whites on a worldwide scale; the Southeast Farallon Island in Greater Farallones National Marine Sanctuary, a marine and wildlife refuge off the coast of California is another location where sharks make themselves scarce when orcas are near. “When confronted by orcas, white sharks will immediately vacate their preferred hunting ground and will not return for up to a year, even though the orcas are only passing through,” scientist Salvador Jorgensen explained in a press release back in 2019.
It is unclear how many shark-eating orcas aside from Port and Starboard there are off the coast of South Africa and whether this behavior will spread to newer generations. It is worrying, however, how much of an environmental shake up two orcas have caused… and what havoc more might cause.