This article first appeared on ntv.de
Two killer whales (orcas) caused a veritable massacre among sharks off the coast of South Africa at the end of February. In a single day, the whales killed a total of 17 sharks, marine biologist Alison Kock reported on Twitter. The animals' carcasses drifted ashore at Pearly Beach, a village on the southernmost tip of South Africa.
"At least 17 sevengill sharks were killed by the infamous pair of killer whales Port and Starboard in South Africa this week," the scientist wrote on Twitter on February 24. The names port and starboard are the English terms for port and starboard. The animals were given this name because the dorsal fin folds away to the right in one specimen and to the left in the other.
The orcas had again only eaten the livers of the broadnose sevengill sharks (Notorynchus cepedianus). This behavior had previously been observed. The reason for this could be that shark livers are very nutritious and contain large amounts of fats and vitamins. "Orcas may have learned that eating shark livers provides a lot of energy and nutrients," Kock told online magazine Live Science.
Another characteristic of the liver could favor the preference of the whales: "Shark livers are large and buoyant and rise to the surface of the water when a shark is killed," Kock told the magazine. This makes them easy for orcas to recognize and access, while other organs sink to the bottom or are harder to find.
According to Kock, the practice of eating the liver had been observed in the couple for eight years. "We first observed this pair hunting sevengill sharks in False Bay, Cape Town in 2015 (...) the drama didn't stop there," she wrote on Twitter. In 2017, the couple finally started hunting great white sharks and eating their livers. Eventually, this caused the sharks to abandon their accustomed places offshore.