The great white shark is actually at the top of the food chain in the oceans. In front of South Africa's Western Cape, however, the species is being contested by powerful competitors. In the meantime, the sharks hardly appear in one of their preferred hunting grounds. This throws the ecosystem out of balance.
In South Africa, a pair of orcas kills and expels great white sharks from their natural habitat. Great white sharks are now fearfully avoiding the coastal area around Gansbaai, previously considered one of the most legendary areas in the world for sighting the giant predators, according to a study published in the African Journal of Marine Science.
Since 2017, eight great white sharks have washed ashore in the region after an orca attack, according to the study. Seven of them were missing their livers, and some were missing their hearts - wounds clearly inflicted by the same orca couple. Researchers suspect it also killed other great white sharks that didn't wash ashore. The very intelligent orcas (killer whales) are distributed worldwide and feed on fish and seals, among other things.
The results of the study, which began in 2017, indicate that the attacks have triggered a rapid and long-term mass displacement of great white sharks. Great white shark sightings have "decreased dramatically" in Gansbaai since 2017. Gansbaai is located in South Africa's Western Cape Province. The place attracts tourists from all over the world who want to see great white sharks from dive cages. "We are observing a large-scale avoidance strategy. The more often the orcas visit these sites, the longer the great whites stay away," said study lead author Alison Towner.
The absence of great whites is unprecedented in the region and is transforming the marine ecosystem, Towner said. Fewer great white sharks, for example, led to greater numbers of Cape fur seals. This has a negative impact on the endangered African penguins that the seals hunt.
Data that has not yet been published indicates that the presence of orcas, also known as killer whales, is increasing in the coastal regions of South Africa. It's thought the pair of orcas may belong to a rare shark-eating subspecies that preys on at least three species of sharks. The changes in hunting behavior could be related to a decline in various fish populations that were previously prey for orcas, Towner said.
(This article was first published on Thursday, June 30, 2022.)