Orca (Killer Whale)

The Lowdown

The orca (Orcinus orca) is the largest member of the dolphin family and the ocean’s apex predator, with no natural predators once grown, though young orcas may be attacked by other killer whales or large sharks. Orcas rely on underwater sound to feed, communicate, and navigate. The Southern Residents, a fish-eating population in the eastern Pacific, hunt by echolocation, clicking out sound and reading the echoes so precisely that they can tell one salmon species from another. Echolocation lets killer whales detect fish up to 500 feet away, much farther than they could see in dark water. Each pod also has its own dialect of calls, learned and culturally passed on between whales, and one study puts the average detection range of resident orcas’ long-range calls at 10 to 16 kilometers, about 6 to 10 miles, in a calm sea.

Different ecotypes have their own learned hunting tactics. Off the Antarctic Peninsula, groups of pack ice killer whales work together to make waves that wash Weddell seals off ice floes. In one study they caught 12 of the 16 Weddell seals they attacked, and a successful attack took four waves on average. Off northern Norway, orcas use carousel feeding: they herd herring into a tight, dense ball near the surface, then slap its edge with their tail flukes to stun the fish before eating them one by one.

Dialects that shift A study that recorded two resident orca families for 12 to 13 years found one of their call types changing, in a similar way in both families. Hunting skills are taught as well, passed to younger whales in the pod through apprenticeship.

Off the coast of South Africa, a killer whale has been filmed trying to roll a great white shark upside down, into a position that sends sharks into tonic immobility, a paralysis-like state, before biting into its abdomen just behind the pectoral fins. That matches the attack researchers had suspected from shark carcasses missing their livers, and one study estimated that the liver of an adult white shark of about 428 kilograms holds roughly as much energy as an adult male orca needs in a day. At California’s Southeast Farallon Island, transient orcas killed a white shark in 1997 and ate only its liver. In 2009, orcas stayed just over two and a half hours and were not seen killing any shark, yet the island stayed virtually shark-free for the rest of that season.