Surprise attack: solo orca kills great white
● An orca has, for the first time, been seen hunting and consuming a great white shark on its own.
In under two minutes, start to finish.
“The astonishing predation, off the coast of Mossel Bay, represents unprecedented behaviour, underscoring the exceptional proficiency of the ‘killer whale’,” says Rhodes University scientist Alison Towner, who led the international research team that revealed the attack in the African Journal of Marine Science.
The same team found that the orca, nicknamed Starboard, and its predatory partner, Port, have worked as a pack to hunt white sharks off this coastline since 2017. When the pair enter a patch of ocean favoured by white sharks, they have been tracked swimming away from the sites where they are known to congregate.
This time, Towner says, they “witnessed an orca, nicknamed Starboard — due to his collapsed dorsal fin — performing alone to incapacitate and consume a white shark. Starboard was observed preying on a 2.5m juvenile white shark, later carrying the shark’s liver in its mouth past a boat.”
Another white shark carcass of 3.55m was found nearby.
Towner says the new discovery provides further insight into how mammalian predators specialise and diverge ecologically.
Usually orcas work together to take down large predators, including sea lions, whales and sharks. They use their shared intelligence and strength to surround and kill their prey, says Towner, a senior biologist who has studied the movements of white sharks for 17 years.
Marine scientists warn that plummeting populations of smaller sharks from overfishing are a greater threat to white sharks than orcas.
The latest South African white shark film, Shark Eat Shark, says most white shark hunting seems to be of small sharks close to the ocean bed near estuaries, despite dramatic footage of them breaching to catch seals near Seal Island off Mossel Bay.
Dr Enrico Gennari, an eminent white shark scientist, and his team discovered that the white sharks of Mossel Bay regularly prey on smaller sharks such as smooth hound sharks.
Gennari, founder of the Oceans Research Institute, and scientist Lacey Williams set up underwater bait traps, tracked the white sharks with tags and drones, and took tissue samples off the back of swimming sharks to gather evidence to support their findings.
Citizen science by observers, tourists and collaborating institutions is also playing a role in collecting data and footage on white sharks.
Esther Jacobs of the marine conservation initiative Keep Fin Alive, saw the unprecedented solitary orca attack.
“Witnessing a white shark’s fin break the surface [near Seal Island] initially sparked excitement, but that turned to a sombre realisation as Starboard swiftly approached. The moment Starboard preyed on my favourite shark species was devastating.”
Towner says the orcas are again “exhibiting a strong preference for extracting and consuming the lipid-rich livers of white sharks — a specialised feeding behaviour”.
A drop in the white shark population affects the marine ecosystem, as the apex predators control the population of predators lower down the food chain.
“Whatever our feelings about sharks, humans need them,” says shark scientist Sophu Qoma. “They are apex predators, which means they are at the top of the food chain and balance the ecosystem. If you take out an apex predator in the ecosystem, there will be a collapse of that whole system.”
The new study, published in the peerreviewed African Journal of Marine Science, raises questions about orca predation on shark populations in South Africa cascading through the ocean.
The co-author of the study, Dr Primo Micarelli, from the Shark Studies Centre and Siena University in Italy, says: “Over two decades of annual visits to South Africa, I’ve observed the profound impact these killer whales have on the local white shark population. Seeing Starboard carry a white shark’s liver past our vessel is unforgettable. Despite my awe for these predators, I’m increasingly concerned about the coastal marine ecology balance.”