Summary
In 2017, several great white sharks washed up dead near Gansbaai, South Africa with their livers removed, and researchers linked the deaths to orcas. Great whites then largely left the area, and a later peer-reviewed study (Towner and colleagues, 2022) tied their absence from South Africa’s largest aggregation site to killer whale predation. The great white shark is listed as Vulnerable on the IUCN Red List and in CITES Appendix II. The episode shows that even apex predators are vulnerable and that marine food webs can shift quickly, although the orca behaviour is not shown to be climate-driven.
A striking series of events unfolded on the beaches near Gansbaai, South Africa in 2017. Over a few months, several great white sharks, reported as four to five animals, were found washed up dead, each with its liver removed with surgical precision. Marine scientists concluded that orcas (killer whales) were responsible, taking the nutrient-rich livers.
Why does the Gansbaai case matter for ocean ecosystems?
Because it shows that top predators can be displaced as well as hunted. Great white sharks (Carcharodon carcharias) are apex predators, and the IUCN Red List classifies the species as Vulnerable, with pressure from fishing, bycatch and other human activity. They are protected in South Africa and listed in Appendix II of CITES, which regulates international trade.
Orca predation on great whites was not entirely new, since orcas had been documented attacking them in California waters. However, the Gansbaai cases were the first of this scale recorded in South Africa. Observers reported that great whites disappeared from their usual sites around Gansbaai after the orca visits, and a 2022 study in the African Journal of Marine Science described killer whale predation as the likely driver of the sharks’ absence from this aggregation site. The absence also affected the local shark-viewing tourism industry.
The WWF notes that great white sharks help keep ocean ecosystems healthy by regulating prey populations, so decline or displacement can ripple through marine food webs. Whether climate change will change predator-prey patterns like this is an open question, since warming alters ocean temperatures and prey distribution, but the Gansbaai episode itself is not shown to be caused by it.
How are great white sharks protected in the EU, the UK, the US and Canada?
- International: CITES Appendix II regulates trade in great white sharks and their parts.
- EU and Germany: the EU Wildlife Trade Regulations implement CITES, and EU rules require that sharks are landed with fins naturally attached.
- UK: CITES is implemented through the Control of Trade in Endangered Species Regulations 2018, and the UK bans shark finning.
- US: the Shark Conservation Act of 2010 requires fins to stay naturally attached, and the Magnuson-Stevens Act governs fisheries.
- Canada: amendments to the Fisheries Act ban the import and export of shark fins that are not attached to the carcass, and CITES is implemented through WAPPRIITA.
Frequently Asked Questions
Do orcas really hunt great white sharks?
Yes. Documented cases exist off California and South Africa, and orcas often target the liver, which is rich in energy. The behaviour appears to be learned by particular orca groups, not shown by all orcas.
Are great white sharks endangered?
The IUCN lists them as Vulnerable globally. Regional populations can be in worse condition, and the species is protected by law in many countries.
Is the Gansbaai episode caused by climate change?
There is no evidence that it was. It shows how quickly predator dynamics can shift, which is relevant as warming changes ocean conditions.
Where can I find the original research?
Search for Towner and colleagues (2022), Fear at the top: killer whale predation drives white shark absence at South Africa’s largest aggregation site, in the African Journal of Marine Science.
Related reading
How Plastic is Killing Marine Life | Climate Change: Facts and Solutions | Sustainable Development Goals (SDG 14, Life Below Water)