Orcas, also known as killer whales, are apex carnivores at the top of the marine food web. Classified as the largest species within the oceanic dolphin family, they are one of the ocean’s most formidable predators. Their reputation as a “whale killer,” stemming from ancient observations of their hunting behavior on larger cetaceans, accurately reflects their purely meat-based diet.
Defining the Orca Diet
Orcas are generalized predators globally, but individual populations often exhibit highly specialized feeding behaviors based on local prey availability. Their carnivorous diet is extraordinarily broad, encompassing nearly all forms of marine animal life. Prey includes marine mammals such as seals, sea lions, porpoises, and other whales, alongside a variety of fish, including schooling species like herring and large salmon. They also consume cephalopods like squid and octopus, as well as seabirds and sea turtles. Orcas rely entirely on the high caloric density of animal tissue, as they do not consume vegetation.
Cooperative Hunting Strategies
The success of the orca as a predator is due to its high level of social intelligence and cooperative hunting strategies, which are taught and refined within the pod. One coordinated technique is creating a powerful wave to capture seals resting on ice floes in Antarctic waters. Several orcas swim in a synchronized line, generating a large wave that washes over the ice, knocking the seal into the water where the pod waits.
Another sophisticated group strategy is “carousel feeding,” employed when targeting schooling fish like herring. The pod herds thousands of fish into a dense, tightly packed ball near the water’s surface. Once concentrated, the orcas take turns stunning them with powerful tail-slaps, which disorients or kills dozens of fish with a single blow. When pursuing larger prey, such as a humpback whale calf, a coordinated, high-speed pursuit is employed, with different pod members isolating, exhausting, and restraining the target.
Ecotypes and Dietary Specialization
Orca populations are divided into distinct “ecotypes,” which are genetically separate groups that have developed unique physical traits, vocalizations, and strict dietary specializations. In the North Pacific, three primary ecotypes—Resident, Transient (or Bigg’s), and Offshore—inhabit the same general waters but never interbreed or share food.
Resident Ecotype
The Resident ecotype subsists almost exclusively on fish, preferring Chinook salmon. They locate prey using frequent echolocation clicks and complex vocal communication.
Transient Ecotype (Bigg’s Killer Whales)
The Transient ecotype, commonly referred to as Bigg’s killer whales, feeds only on marine mammals, including seals, sea lions, and other cetaceans. To avoid alerting their sound-sensitive prey, Bigg’s orcas hunt in small groups and operate almost entirely in silence.
Offshore Ecotype
The Offshore ecotype travels in large pods far from the coast and is less studied. This group specializes in consuming fish and sharks. The wear on their teeth suggests they frequently prey on the abrasive skin of sleeper sharks.