A decade ago, up to 1,000 of the apex predators lived in one South African bay. Now they have gone, fleeing from killer whales. But the gap they have left creates problems for other species

The first carcass of a great white, a small female, washed up in South Africa on 9 February 2017. The 2.6-metre-long body had no hook or net marks, ruling out human involvement. Whatever had killed her had vanished. So too had all the other great white sharks in Gansbaai on the Western Cape, Dr Alison Towner noticed.

“We had several sharks acoustically tagged, and later realised three had moved as far as Plettenberg Bay and Algoa Bay, more than 500km [300 miles] east,” says the Rhodes University marine biologist.