A pair of orcas known as Port and Starboard went on a killing spree last month, slaughtering at least 17 broadnose sevengill sharks in a single day off the southern tip of South Africa. The killer whales’ murderous behavior had a clear motive – they love to eat shark livers and have become adept at working as a team to take down their prey.
A shark’s liver is rich in fats and nutrients including a sought-after organic compound known as squalene. It's a large, buoyant organ that killer whales can easily locate and remove – they simply rip open the shark’s pectoral girdle. Orcas clearly prefer liver over the rest of the shark, as Port and Starboard left the remainder of the carcasses intact to wash ashore.
The two orcas are known to locals in the small fishing port of Gansbaai and are easily recognized by their twisted dorsal fins. They first appeared in the area in 2015 and are fairly unique among orcas because they like to hunt near the coast.
Killer whales are known for their intelligence and cooperation when hunting, either in pairs or groups. They learn quickly from experience and from other group members so they can work together to surround, confuse, and incapacitate their prey, making it easier to kill even the largest and most fearsome creatures in the ocean, such as great white sharks.
Killer whales that live up to their name:
- Last year, a drone filmed Starboard and four other orcas taking down a great white shark near Mossel Bay. The attack worried biologists because it indicates that orcas are learning hunting techniques from one another that are driving sharks from their habitats and ecosystems. It already seems that Port and Starboard’s hunting exploits are encouraging white sharks to leave the Cape Town area.
- In other parts of the world, orca pods have been observed flipping great whites over onto their backs, causing them to enter a trance-like state known as tonic immobility. This gives orcas around a minute to locate and target the liver.
- Although shark liver is clearly a favorite menu item, orcas have been known to eat pretty much anything, including fish, dolphins, octopus, sea birds, seals, and even other whales. An adult can consume up to 500 lbs (227 kg) of food in a day.