A pair of killer whales (Orcinus orca) have (once again) been living up to their name, terrorizing great white shark communities off the coast of South Africa for the last five years. Since 2017, the deadly duo has killed at least eight great whites, ripped them apart, and devoured their livers (in all but one case).
In their bloodthirst, the two males even sometimes removed their victims' hearts. Port and Starboard, as they’re rather innocuously nicknamed, are still at large and on the rampage near South Africa’s Gansbaai coast.
Their reign of terror is reported in a study published in the African Journal of Marine Science, which followed the great whites' movements for several years. In the wake of the orcas’ killing spree, it seems the sharks may have been frightened away, the study finds.
Since 2017, eight great white sharks (Carcharodon carcharias) washed up on beaches in Gansbaai, Western Cape Province, sporting signs of an orca attack. The majority – five carcasses – were found between February and June 2017, a particularly murderous period for the whale pair. The wounds were all made by the same two orcas and each death corresponds to a sighting of the pair – pretty damning evidence that has made Port and Starboard, recognizable from their collapsed dorsal fins, prime suspects.
It’s likely that this is just the tip of the iceberg of their crimes – plenty more great whites could have been slain but never washed up on shore.
Perhaps in response, great white sharks have seemingly scarpered. And who could blame them? According to the new research, there were around six great white sightings a day before 2017. In the six months following the killer whale attacks, this dropped to around one and stayed low (below two) throughout 2018 and 2019.
Electronic tracking data tells a similar story and shows that in the days following an orca attack, some sharks swam hundreds of kilometers away from Gansbaai. One particularly intrepid shark swam 900 kilometers (560 miles) east and was detected north of East London.
“What we seem to be witnessing … is a large-scale avoidance (rather than a fine-scale) strategy,” the study’s lead author Alison Towner said in a statement. “The more the Orcas frequent these sites, the longer the Great White Sharks stay away.”
Their unprecedented absence has made way for some shifts in the ocean ecosystem, Towner noted.
“It has triggered the emergence of a new mesopredator to the area, the Bronze Whaler Shark [Carcharhinus brachyurus] – which is known to be eaten by the Great White Shark.” The new sharks on the block are not safe from the orcas’ wrath, either, and are also being attacked, Towner added.
This change to the natural order could have devastating impacts further down the food chain too: “With no Great White Sharks restricting Cape Fur seal behavior, the seals can predate on critically endangered African Penguins, or compete for the small pelagic fish they eat,” Towner explained.
And what of the potential agents of all this chaos? Port and Starboard’s murderous motivations are unclear. It could “be related to a decline in prey populations” of both species, Towner suggested. Or, the pair could be members of a rare subspecies of killer whales known to hunt sharks.
Or, just maybe, this wasn’t their doing after all. The decline of great white sharks could also be the result of fishing or fishing-induced declines in prey, the authors suggest. The jury’s still out. Either way, Port and Starboard are free to slay another day.