South African researchers, led by the University of Rhodes, have been connecting trackers to 14 sharks since the killer whale attacks began in 2017. They found evidence of an “immediate exit” after the two whales killed at least five large whites. in six months.
The data show that sharks responded quickly to the new threat and ceded the territory to the new apex predator of the block. However, another shark, the bronze whale, has moved to the area.
This smaller shark is often eaten by large whites and is prepared to take the risk of killer whales in exchange for abundant food, the researchers say.
The removal of large white from the area and the insurrection of killer whales and the bronze whale means that the balance of power at the top of the food chain is drastically different, and problems are likely to fall across the ecosystem.
Change in the behavior of major predators
Researchers now believe that killer whales not only maximize their available food by killing and eating other predators, but are actively opening a new niche as shark eaters.
Alison Towner, author of the study and senior white shark biologist at the Dyer Island Conservation Trust, said: “This change in the behavior of the two main predators could be related to a decline in prey populations, including fish and sharks, causing changes in their distribution pattern.
“Killer whales target large subadult white sharks, which may further affect an already vulnerable shark population due to their slow growth and late maturing life history strategy.
“Increased surveillance through citizen science (e.g., fishermen’s reports, tourist boats), as well as ongoing monitoring studies, will help gather more information on how these predations can affect long-term ecological balance in these complex coastal seascapes “.
The research is published in the African Journal of Marine Science.