Terrorized by killer whales, great white sharks flee

Great white sharks (Carcharodon carcharias) are about six meters long, weigh more than 2,000 kilos and have a jaw capable of exerting a pressure of 1.8 tons. One could easily believe that they fear no one. And yet, terrified by the actions of two orcs (Orcinus orca), some have preferred to abandon their living area off the coast of South Africa.

Killer whales that have made sharks a prime target

For years, great white sharks had settled off the coast of Gansbaai, a place where they dominated the food chain. But everything changed in 2017. Science and Future echoed the attacks of killer whales on sharks. Since that year, eight great whites have been found washed up on a beach. Seven had had their liver eaten (this organ in the shark is particularly rich in lipids) and others had also had their heart eaten. “Their wounds were made by the same pair of orcs (probably males, editor’s note), who probably killed more (who didn’t wash up on shore). It is widely believed that other orcas are also capable of such attacks.“, notes a press release.

These mammals have a very impressive morphology. They can reach a height of nine meters and weigh more than 6,000 kilos. And the duo that terrorizes the great white sharks also seems to belong to a rare morphotype (the morphotypes group together individuals of the same species with specific physical characteristics, such as the size or the shape of the fin) of killer whales shark eaters. These two killer whales, baptized Port and Starboard by the researchers, would have flatter teeth than those of their congeners who attack marine mammals.

A prolonged absence

A new international study published on June 29, 2022 in the journal African Journal of Marine Science and carried out for more than five years made it possible to follow the movements of 14 sharks. She reveals that sharks largely flee the area when killer whales are present. So far, great white sharks have only been absent from Gansbaai for four weeks since their presence began to be recorded: one week in 2007 and three weeks in 2016. Tourists flocked to the area to observe these mythical animals.

Then, “initially, following an orca attack in Gansbaai, great white sharks would not appear for weeks or months. What we seem to be witnessing is a large-scale avoidance strategy“, notes Alison Towner, lead author of the study. They migrate rapidly, en masse, away from the terrible pair. This prolonged absence is unprecedented in this region of Africa.

Their escape alters the local ecosystem and can lead to cascading reactions. In the absence of great whites, copper sharks (Carcharhinus brachyurus), yet also hunted by killer whales, have become important predators of the landscape. Researchers expect a restructuring of trophic relationships in the region. “Balance is crucial in marine ecosystems. For example, without a great white shark to limit the behavior of South African fur seals, they can prey on the critically endangered African penguins.“, warns Alison Towner. Biologists will closely monitor new interactions off the coast of Gansbaai.

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