Great Whites Are Vanishing Because of Two Ruthless Orcas

The white shark (Carcharodon carcharias), with its sleek, optimized hunting body and razor-sharp teeth, is widely considered one of the ocean’s top predators. No other sea creature inspires as much terror, rightly or wrongly. While this is generally true, scientists have recently confirmed that there is something even the great white fears.

Since 2017, great white sharks have made themselves extremely scarce off the coast of South Africa, an area where they usually congregate. Initially, this strange disappearance was attributed to human activity, such as overfishing. However, subsequent research uncovered a far more specific and predatory cause.

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What Ocean Predator Scares Great White Sharks Away?

The great white shark is widely regarded as one of the ocean’s top predators due to its razor-sharp teeth and body built for hunting. Despite its reputation, scientists documented the sharks becoming extremely scarce off the coast of South Africa starting in 2017.

Later research confirmed that the scarcity was not primarily due to human activity, like overfishing, but rather the presence of a superior predator: a pair of orcas (Orcinus orca).

Which Two Orcas Are Attacking Great White Sharks in South Africa?

The true culprits behind the shark scarcity are a pair of orcas nicknamed Port and Starboard. They are easily identifiable by the distinctive kinks in their dorsal fins. These two were confirmed to be hunting the sharks specifically to slurp out their delicious, nutritious, vitamin-rich livers.

The town of Gansbaai, once considered the great white shark capital of the world, has seen the sharks’ presence diminish dramatically. Since 2017, at least nine great white sharks have washed ashore there. Several of these carcasses were missing their livers, and some were also missing their hearts—the clear hallmark of an orca attack.

The wounds observed on these sharks are distinctive and have been traced back to Port and Starboard. Scientists believe the pair are responsible for many more great white deaths that never washed ashore. White sharks are not their only victims either; Port and Starboard have been implicated in a killing spree that wiped out at least 17 broadnose sevengill sharks in a single day, with only the livers eaten and the leftover carcasses washing ashore.

Do Great White Sharks Flee Permanently When Orcas Appear?

The presence of orcas can drive great white sharks away almost instantly. Studies have shown this avoidance behavior previously; for example, research off the coast of San Francisco found that great whites abandon their preferred hunting waters as soon as an orca appears.

Marine biologist Alison Towner and her team confirmed that orcas are the reason sharks are starting to avoid their favorite South African spots. Following an orca attack in Gansbaai, individual great white sharks often did not return for weeks or even months.

In one long-term study, 14 GPS-tagged sharks were tracked over five years and were seen to flee the area whenever orcas were present. Researchers describe this as a large-scale avoidance strategy, similar to how wild dogs in the Serengeti avoid lions.

This scale of avoidance is unprecedented. Since record-keeping began in Gansbaai, great white sharks had only been absent for a week or more on two occasions: once for a week in 2007, and once for three weeks in 2017. The current disappearances are ongoing and significantly longer.

How Does the Absence of Great Whites Change the Coastal Ecosystem?

The loss of great white sharks is altering the ecosystem of the coastal seascapes. In their absence, copper sharks (Carcharhinus brachyurus), which are normally preyed upon by great whites, are moving in to fill the vacant ecological niche.

The orcas are now hunting these copper sharks instead. Observations suggest that the orcas have developed remarkable skill in targeting large sharks, displaying techniques refined through experience.

But the absence of great whites has wider consequences. Without them restricting Cape fur seal behavior, the seals are free to prey on critically endangered African penguins or compete with them for the small pelagic fish they both eat. This represents a “top-down” ecological impact. Compounded by “bottom-up” pressures, such as the extensive removal of abalone, the ecosystem is under stress. Scientists warn that there is only so much pressure an ecosystem can take, and the impacts of orcas removing sharks are likely far wider-reaching.

Why Do Orcas Only Eat Shark Livers, and What Is the Long-Term Risk?

Orcas target shark livers because they are rich sources of nutrition huge, plump, and packed with fats and oils. Sharks use these reserves to fuel their long migratory journeys across the ocean. What remains unclear is how the orcas developed such a precise hunting technique or why they prefer livers over other parts of the shark.

Some orcas may now be adapting to hunt sharks preferentially, possibly due to declining numbers of their traditional prey. This new predatory pressure is highly concerning for conservationists, as great white populations are already vulnerable and in decline worldwide.

The risk is even greater because the orcas are targeting subadult great white sharks. This is particularly damaging given their slow growth and late-maturing life cycle. To fully understand how these predations affect the long-term ecological balance, scientists recommend increased vigilance, including reports from fishers, tourism vessels, and continued tracking studies.