The orca, or Orcinus orca, is the largest member of the oceanic dolphin family, instantly recognizable by its distinct black and white pigmentation. Found in every ocean on Earth, from the frigid polar regions to the warmer tropical seas, this marine mammal occupies the position of the ocean’s apex predator. Orcas are highly intelligent, social animals that hunt in coordinated groups, earning them the nickname “wolves of the sea.” While the species has a global distribution, its diet is not uniform; instead, it is incredibly diverse, reflecting adaptability to different marine environments and available prey.
Primary Categories of Orca Prey
Globally, the orca’s diet is extensive, encompassing a vast array of marine life from the smallest schooling fish to the largest baleen whales. Studies have documented that orcas prey on over 140 animal species worldwide, showcasing their opportunistic yet specialized nature. The variety of food items consumed includes bony fish, cephalopods, marine mammals, and even marine birds and reptiles.
Fish are a major component of the diet for many orca populations, with examples like Pacific salmon, Norwegian herring, and various species of cod frequently targeted. Orcas that specialize in fish often focus on large, nutrient-rich species like Chinook salmon, which provide the high-fat content necessary to sustain their large bodies. Mammal-eating populations focus on seals, sea lions, porpoises, dolphins, and larger prey like minke whales. The diet also includes cephalopods, such as squid and octopus, and unusual prey items like seabirds and leatherback sea turtles, which are generally taken opportunistically.
Dietary Specialization and Ecotypes
The immense dietary diversity observed across the species is best understood through the concept of ecotypes, which are distinct populations that differ genetically, physically, and culturally. In the North Pacific, three main ecotypes—Resident, Transient (Bigg’s), and Offshore—demonstrate a strict segregation in their prey preferences, rarely interbreeding or interacting. This specialization means that orcas adhere strictly to their inherited, culturally-learned menu.
Resident Orcas
Resident orcas are fish-specialists, with their diet consisting almost exclusively of fish. In the Pacific Northwest, these whales show a pronounced preference for salmon, particularly the large and fatty Chinook salmon, which can account for up to 96% of their total diet. They are not known to eat marine mammals.
Transient Orcas
Transient orcas, also known as Bigg’s orcas, are strict mammal-eaters, preying on seals, sea lions, porpoises, and other cetaceans. These groups will not consume fish, reflecting a deep, cultural divide in foraging behavior. Their hunts often target the largest available prey, including gray whale calves and minke whales.
Offshore Orcas
The third group, Offshore orcas, is less understood due to their distance from the coast. Their diet appears to be dominated by deep-sea fish and sharks. The severe wear observed on the teeth of Offshore whales is believed to result from the rough, abrasive skin of the sharks they consume. Evidence also suggests they may selectively prey on the nutrient-rich livers of sharks.
Coordinated Hunting Techniques
The wide range of prey available to orcas necessitates a diverse and sophisticated set of hunting techniques, most of which rely on remarkable social coordination. When targeting dense schools of fish like herring, Norwegian orcas employ a strategy called “carousel feeding.” The pod works together to herd the fish into a tight, compact ball near the surface by using streams of bubbles and flashes of their white undersides. They then stun the fish by tail-slapping the ball before consuming the immobilized prey.
For mammal-eating populations, a technique known as “wave washing” is used to dislodge seals resting on ice floes in the Antarctic. A group of orcas will swim in tight formation toward the ice, creating a powerful, synchronized wave that washes over the floe, knocking the prey into the water. The whales may repeat the process until the seal is secured.
Transient orcas also demonstrate specialized strategies for taking down large whales. They use sustained, coordinated attacks to separate a calf from its mother, wearing down the prey over hours. Other distinct techniques include intentional, temporary beaching, where orcas in places like Argentina will slide onto the shore to grab sea lions before using a wave to pull themselves back into the water. These specialized methods are culturally learned behaviors passed down through generations within the pod.