Since 2017, a pair of male orcas have been terrorizing the coast of Gansbaai in South Africa, which used to be a popular place for great white sharks to live and hunt. These creatures have killed a number of sharks and consumed their oil-rich livers and sometimes hearts, while experts study the carcasses of the terrifying predators that wash ashore.
Although killer whales are notorious for devouring everything from small fish to the occasional blue whale, scientists have warned that these killer whales are now having a major impact on their habitat.
In a new study published in the African Journal of Marine Science, researchers have found that great white sharks have been avoiding the region since the two orcas took over.
Through a combination of tagging data and long-term shark sightings, the scientists found that the sharks, which used to be dominated along the coast of Gansbaai, are actively avoiding the region.
Lead study author Alison Towner, a senior biologist who studies white sharks at the Dyer Island Conservation Trust in South Africa, said in a statement: “What we seem to be seeing, however, is a large-scale avoidance strategy, reflecting what we see being used by wild dogs.” in the Serengeti in Tanzania, in response to the increased presence of lions.
“The more often the killer whales visit these sites, the longer the great white sharks stay away.”
The researchers added that they have never seen anything like the attacks.
Ms Towner wrote: “They work together and rip the shark open by the pectoral fins, tearing it open.”
She added that the region’s ecosystem had already begun to “shift” to compensate for the absence of the great white sharks.
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They found that even the number of sharks detected after being tagged with electronic transmitters also decreased.
Before the threatening killer whales came to the region, between three and eight tagged sharks were detected in the area each day, which then dropped to zero.
Days after the killer whales slaughtered a shark, the transmitter signal would reveal that the rest of the fearsome fish sometimes swam away by the hundreds of thousands and stayed there for six months or more before returning.