When two orcas arrived in False Bay, Cape Town, great white shark sightings dropped dramatically. Eight years later, the sharks still haven't returned.

A whodunnit has been playing out in False Bay on the Cape Peninsula for nearly a decade, and the mystery might finally be solved. Like a round of marine Cluedo, the evidence points to the most likely culprits behind the bay's missing great white sharks: the killer whale pair, Port and Starboard, who earned their nautical nicknames because of their distinctive left- and right-lilting dorsal fins.

The two became regular visitors to the bay in 2015 and, almost overnight, the white sharks vanished along with their dramatic seal-hunting aerial manoeuvres that have been freeze-framed for the world's pleasure by so many photographers.

Some simple number-crunching of shark data spanning half a century confirms the many eyewitness accounts that put these two orcas in the crosshairs as investigators tried to explain the sharks' sudden disappearance from this sheltered nook of the Atlantic eight years ago.

Thankfully, researchers conclude, these findings confirm that the southern African population of this globally threatened shark species isn't dying out. They're simply fleeing the Cape and heading eastwards into safer waters.

Researchers have only recently come to know how wide-roaming these sharks are, and that individual animals trek easily between the Cape and the waters off...