The great white shark, also known as Carcharodon carcharias, has long been considered one of the ocean’s top predators, instilling fear in many with its sleek body, razor-sharp teeth, and reputation for enjoying human flesh. However, recent research has revealed that even the great white shark has something to fear – a pair of orcas known as Port and Starboard.
Since 2017, scientists have noticed a significant decrease in the presence of great white sharks off the coast of South Africa, particularly in the fishing town of Gansbaai, where they usually congregate. Initially, this decline was attributed to human activities such as overfishing. However, in 2022, research confirmed that the true reason for the sharks’ disappearance was the hunting activities of Port and Starboard, who were targeting the sharks and extracting their livers.
Port and Starboard, named for the distinctive kinks in their dorsal fins, have been implicated in multiple attacks on great white sharks, leaving many of them washed ashore without their livers. Additionally, the orcas have been responsible for killing other species of sharks in the area, such as broadnose sevengill sharks.
Studies have shown that the presence of orcas can drive great white sharks away from their preferred hunting grounds. Researchers, led by marine biologist Alison Towner, have tracked the movements of tagged sharks and observed how they flee the area when orcas are present. This avoidance behavior has led to a significant decrease in shark sightings in several bays, indicating a large-scale shift in shark behavior.
The absence of great white sharks has had ripple effects on the ecosystem, allowing other species, such as copper sharks, to fill the vacant ecological niche. This shift in predator dynamics has the potential to alter the balance of the marine ecosystem, leading to unforeseen consequences.
As researchers continue to study the interactions between orcas and great white sharks, it becomes increasingly clear that the impacts of these predator-prey relationships extend far beyond the individuals involved. Understanding these dynamics is crucial for maintaining the health and balance of marine ecosystems, highlighting the interconnectedness of species and the delicate balance that exists within these complex systems. The liver of a shark is a rich source of nutrition, containing fats and oils that fuel their migratory journeys across the ocean. Orcas have been observed targeting sharks for their livers, but it remains unclear how they discovered this as a preferred food source.
Some theories suggest that orcas may be adapting to hunt sharks due to a decrease in their usual prey. In addition to targeting great white sharks, orcas in the Gulf of California have also developed techniques for hunting whale sharks. However, with great white shark populations declining globally, the added pressure from orcas could have negative implications.
According to researcher Towner, the targeting of subadult great white sharks by orcas could further impact the vulnerable shark population, as they have a slow growth and late-maturing life-history strategy. Increased vigilance through citizen science and tracking studies will be crucial in understanding the long-term ecological balance in these coastal seascapes.
The team’s research on this phenomenon has been published in the African Journal of Marine Science. It is important to continue monitoring these interactions between orcas and sharks to better understand the implications for marine ecosystems.
An earlier version of this story was published in July 2022.
