Great white sharks are being killed in disturbing fashion off South Africa, and experts are helpless to prevent further assaults.
That's because orcas are believed responsible for the killings. At least three white shark carcasses have washed ashore recently with similar injuries, each with its liver removed.
This bizarre predatory pattern is unprecedented in South Africa, and many hope it'll be short-lived. White sharks are vulnerable from a conservation standpoint, and immensely valuable as tourist attractions.
"Obviously this is a very sad time for us all," Alison Towner, a biologist with the Dyer Island Conservation Trust, stated Sunday after the third carcass was discovered near Gansaabi. "Nature can be so cruel and the dexterity these enormous animals are capable of is mind blowing… almost surgical precision as they remove the squalene-rich liver of the white sharks and dump their carcass."
Gansaabi is one of the world's premiere shark-diving destinations. White sharks generate millions in tourism revenue, but the presence of orcas appears to have frightened the sharks away.
Marine Dynamics, a commercial cage-diving company that also cooperates in white shark research, stated Sunday that its vessel, Slashfin, came up empty in a daylong search. Other companies have likewise complained about the unusual phenomenon.
Though there have been mysterious white shark deaths in the past, they were not confirmed to have been caused by orcas.
Stated Towner, the marine biologist, on Facebook: "It's a very interesting time. The last white shark washed up here on the 8th of February and the cage-diving boats struggled to see any sharks for almost two weeks. Unfortunately the cage-diving boats all came home after seeing no sharks again today."
Orcas, or killer whales, are highly efficient predators who hunt with the precise cooperation of pod members. They do not typically hunt white sharks, presumably because there sharks do not possess a calorie-rich blubber layer.
But sharks do possess large iron-rich livers. (The orcas also removed the heart of at least one of the tree mutilated white sharks.)
To draw a parallel, transient orcas are currently preying on gray whale calves off the California port of Monterey. The killer whales drown the babies after separating them from their mothers, often after an agonizing struggle. The calves are rich in fat, but the orcas often remove the tongue before dining on blubber.