A new threat to great white sharks has emerged off the coast of South Africa. Scientists have identified two orcas, nicknamed Port and Starboard due to their distinctive dorsal fin kinks, as the primary predators behind the decline of great white shark populations in the area.
In 2017, researchers initially suspected human activity was responsible for the sharks’ disappearance, but subsequent studies confirmed that a pair of orcas is hunting and killing great whites. The victims often have missing livers and hearts, a hallmark of an orca attack.
The team tracked 14 GPS-tagged great white sharks over five years, finding that whenever Port and Starboard were present, the sharks would flee. Sightings of great white sharks in several bays are also down significantly since record-keeping began.
This shift has significant implications for the ecosystem. In the absence of great whites, copper sharks are filling their ecological niche, which is being preyed upon by orcas. This can lead to a ripple effect throughout the food chain, with potential impacts on Cape fur seal behavior and the critically endangered African penguin population.
Researchers warn that the removal of great white sharks from the ecosystem may have far-reaching consequences. While it’s unclear why orcas are targeting sharks, their livers are rich in nutrition, fueling their epic migratory journeys. The added pressure on declining great white populations is a cause for concern, particularly as they are vulnerable due to slow growth and late-maturity.
The team’s research has been published in the African Journal of Marine Science, highlighting the need for increased vigilance through citizen science initiatives and continued tracking studies to understand the impact of orca predation on long-term ecological balance.
Source: https://www.sciencealert.com/great-white-sharks-scared-from-their-habitat-by-just-2-predators