A series of mysterious events has left great white sharks largely absent from coastal areas in South Africa. The most recent incident involved two male orcas, identified as Port and Starboard, attacking and killing several great whites off the coast of Mossel Bay.
Dr Alison Towner, a marine biologist at Rhodes University, observed that after each shark was killed, the surviving sharks fled for longer periods before returning to their usual locations. In some cases, they returned in smaller numbers. When another great white was found dead on the beach, Towner and her colleagues conducted necropsies and discovered that all four recent victims had been torn open at a specific spot with surgical precision.
The signs pointed to orcas as the culprits. The two males were frequent visitors to the area and had previously killed sevengill sharks in nearby False Bay. Although direct observation of an attack by Port and Starboard was not possible, footage captured on 16 May 2022 showed five orcas attacking a white shark, biting between its pectoral fins, and ripping out its liver.
One of these sightings confirmed the involvement of Starboard. Another recording, just hours later, showed three more kills, with a helicopter crew witnessing the events unfold. The surviving great whites eventually left Mossel Bay, with some not returning for 45 days.
The disappearance of the sharks from the area has had significant consequences on the ecosystem. With fewer sharks to regulate prey populations, the cape fur seal and bronze whaler shark have surged in numbers, affecting local wildlife. This phenomenon is an example of a trophic cascade, where the loss of a predator can lead to an imbalance in the food chain.
In addition, the decline of sharks has led to increased disease among seals, resulting in outbreaks of rabies in the Western Cape region.
Experts warn that while events like these are alarming, they represent only a small part of the larger issue facing sharks globally. Overfishing is driving a global extinction of many shark species, with more than 100 million killed annually and over a third threatened with extinction.
Strengthening international fishing regulations, expanding marine protected areas, and promoting sustainable fishing practices are key to preventing further ecological damage.
Source: https://www.theguardian.com/environment/2025/jan/23/south-africa-gansbaai-marine-biology-apex-predators-orcas-conquer-great-white-sharks-seals-penguins-trophic-cascade-aoe