In 2017, the carcass of a great white shark washed ashore near Gansbaai, South Africa, with a gaping wound below its pectoral fin and its liver surgically removed. Researchers identified the killers as a pair of orcas already known to local scientists: Port and Starboard, named for their left- and right-leaning collapsed dorsal fins. Within weeks, great whites that had patrolled those waters for years were gone. By 2019, the Shark Spotting Programme in nearby False Bay recorded zero sightings after logging more than 200 in peak years earlier that decade. As of May 2026, the sharks have not returned.
The disappearance triggered a scientific argument that remains unresolved. One group of researchers says orca predation drove the white sharks out. Another insists that decades of human-caused killing had already hollowed out the population, and the orcas simply delivered the final blow. The stakes extend well beyond academic journals: without its apex predator, False Bay’s marine ecosystem has visibly shifted, and the coastal tourism economy that once revolved around shark encounters has contracted with it.
The orca evidence
The most striking direct evidence comes from a 2022 study published in the journal Ecology by Alison Towner and colleagues at the Dyer Island Conservation Trust. The team documented multiple orca predation events on white sharks off South Africa’s coast, including necropsies of five white shark carcasses that showed a consistent pattern: precise wounds and missing livers, the organ richest in energy-dense oils. The study also recorded something that had only been theorized before. Tagged white sharks in the area fled rapidly after orca attacks, abandoning established territories for months at a time.
Port and Starboard, the two orcas linked to the kills, have since been tracked along hundreds of kilometers of South African coastline. Their hunting behavior appears specialized. Unlike most orcas, which feed on fish or marine mammals, this pair targets sharks with what researchers describe as remarkable efficiency. The implication is that even a small number of orca predation events can empty a region of white sharks, not by killing them all, but by triggering a sustained flight response.
The human-mortality case
A separate line of research focuses on a longer, slower form of damage. A 2022 analysis published in Frontiers in Conservation Science used white sharks as a case study in how ongoing human-caused mortality limits recovery for legally protected species. South Africa designated great whites as protected in 1991, but the study found that lethal bather-protection programs, primarily the shark nets and drumlines deployed along KwaZulu-Natal’s beaches, continue to kill white sharks. The researchers’ population modeling concluded that this chronic removal rate can prevent recovery even when a species has full legal protection on paper.
Proponents of this explanation argue that the white shark population entering the late 2010s was already diminished and fragile. A population at full strength, they contend, might have absorbed the pressure of a few orca attacks without collapsing across an entire bay. The orcas, in this reading, were not the primary cause but the trigger that exposed how weakened the population had become.
The geographic nuance matters here. The bather-protection nets are concentrated in KwaZulu-Natal, roughly 1,500 kilometers up the coast from False Bay. Critics of the human-mortality hypothesis note that the nets do not directly affect the False Bay population. Supporters counter that white sharks are highly migratory, and individuals killed in KwaZulu-Natal nets may have been part of the same broader South African population that once frequented the Western Cape.
Ecosystem fallout already measured
Whatever caused the disappearance, its ecological consequences are no longer theoretical. A study published in Frontiers in Marine Science in 2025 by Neil Hammerschlag and colleagues drew on standardized boat-based surveys conducted in False Bay from 2000 to 2020. Over those two decades, the data showed a textbook case of what ecologists call mesopredator release. With great whites gone, mid-level predators, particularly broadnose sevengill cowsharks, increased in abundance. Populations of smaller prey species declined in parallel.
The pattern is consistent with decades of ecological theory: remove the top predator, and the next tier of hunters expands unchecked, suppressing species further down the food web. In False Bay, the shift has been measurable and sustained, not a temporary fluctuation but a structural reorganization of the marine community.
The economic effects are harder to pin down with precision. Cape Town’s shark-cage diving operators, once a significant draw for international tourists, reported steep drops in bookings after sightings collapsed. Some businesses closed or relocated. But no comprehensive institutional survey has tallied the total financial losses across the industry, so the full economic toll remains an estimate rather than a confirmed figure.
What would settle the debate
The honest answer is that no one has yet built the study that could resolve the argument. The orca hypothesis rests on confirmed kills and a documented flight response, but researchers lack long-term baseline data on how often orcas targeted white sharks before scientists began watching for it. Without that historical frequency, it is difficult to say whether the predation pressure of the late 2010s was genuinely new or simply newly observed.
The human-mortality hypothesis relies on population modeling rather than comprehensive counts of sharks killed. Exact removal numbers from bather-protection programs are not publicly available in granular, year-by-year form, which means the scale of human-caused losses is an informed approximation, not a verified census.
The most promising path forward would be a combined population-viability model that integrates both orca predation data and human-removal estimates into a single framework. No published study has attempted this yet. Such an analysis could clarify whether one factor dominates, whether the two interact synergistically, or whether additional variables, such as shifting prey availability or ocean temperature changes, also played a role.
Until that work is done, the scientific community is left with two credible but incomplete explanations supported by strong but partial evidence. What is not in dispute is the outcome: False Bay lost its great white sharks, the ecosystem has reorganized in their absence, and the question of how to bring them back depends entirely on correctly identifying what drove them away.
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*This article was researched with the help of AI, with human editors creating the final content.
