Orcas Are Hunting Great White Sharks and Throwing the Ecosystem Into Chaos

Port and Starboard are rather cutesy names for two of the murderous orcas slaughtering great white sharks off the coast of South Africa at an alarming clip. The local killer whales are so bent on feasting on shark organs that researchers say they’re now affecting the marine ecosystem.

Orcas target white sharks mostly for their livers, which are rich in the nutrients their fellow apex predators crave. The number of sharks in South African waters has been dropping in recent years, most notably in False Bay near the Cape of Good Hope, where white sharks have been absent since 2015. This is a rare instance of a species being hunted to extinction by something other than humans.

While orcas have been killing off great whites at a rate so alarming you’d think they were doing it out of some bloodthirsty quest for revenge, other animals have thrived now that the apex predator, white sharks, have seen their numbers plummet in the past decade.

These cascading effects could be seen in the rise of Cape fur seal populations, which were once kept in check by the great whites. The rise of fur seals means a big decrease in the fish they use as a food source. Similarly, sevengill sharks were longtime competitors/prey for the white shark. With far fewer great whites around, sevengills are thriving.  

Researchers rarely get to see what happens to an environment when the apex predator is all but removed from its ecosystem, but that seems to be exactly what is happening as the South African ocean ecosystem has been destabilized by the lack of white sharks that once kept populations in check.

No one knows exactly why orcas have suddenly taken such a liking to white sharks that it’s become routine to see white shark corpses wash up on shore with their livers missing.

One thing that’s for sure is that it will take a while for the ecosystem to find its balance, and once it does, things will look very different from what they did 10 years ago. Researchers studying the phenomenon think there could be a variety of factors at play, including overfishing and pollution, though they aren’t confident in one explanation over another.