The orca, also known as the killer whale, is the ocean’s apex predator. The question of its favorite food does not have a single simple answer because not all orcas eat the same things. The diet of this highly intelligent marine mammal is not universal but is completely dependent on which specific population, or ecotype, the individual belongs to. This specialization means the prey consumed by one group may be entirely ignored by a neighboring group, establishing distinct dietary traditions passed down through generations.
The Concept of Orca Ecotypes
Orcas are separated into distinct populations called ecotypes, which are genetically and culturally isolated from one another. The three most-studied ecotypes in the North Pacific are Residents, Transients (or Bigg’s), and Offshores, and their diets are mutually exclusive. For example, a Resident orca will almost exclusively eat fish, while a Transient orca consumes only warm-blooded marine mammals. The different ecotypes do not interbreed or interact socially, maintaining unique cultural and dietary traditions. These dietary differences have even led to slight physical variations, such as mammal-eating orcas evolving more robust skulls to handle larger prey.
Diet of Fish-Eating Populations
The diet of Resident orcas, the fish-eating population, provides the closest answer to a “favorite food” for a specific group. For Southern Resident orcas in the Pacific Northwest, their survival is linked to the availability of Chinook salmon. Chinook are the preferred prey because they are the largest Pacific salmon species and possess the highest lipid content, translating into the most energy-dense meal. Chinook can comprise 80% or more of their diet during summer months.
The high-fat content of Chinook salmon is important for meeting the energy requirements of these large predators. Other fish species, such as coho, chum salmon, herring, and halibut, are also consumed, especially when Chinook are scarce. The orcas selectively target larger, older Chinook, which are the most calorically rich fish available. However, their cultural preference means that when populations decline, the orcas struggle to find sufficient alternative nutrition.
Diet of Marine Mammal-Eating Populations
The Transient ecotype, often called Bigg’s orcas, contrasts sharply with Residents by feeding exclusively on warm-blooded prey. Their diet consists of seals, sea lions, porpoises, dolphins, and the calves of larger whales, such as gray whales and minke whales. These orcas are masters of stealth, hunting in smaller groups to effectively stalk their prey. The group’s success relies on surprising their prey, which is why they generally remain silent during a hunt, unlike the more vocal fish-eating Residents.
Prey selection often targets vulnerable individuals, such as young, sick, or isolated marine mammals. The Transient diet requires coordination and power to subdue animals that are often close to their own size. Their survival depends on the abundance of marine mammals, which has led to a recent increase in the Bigg’s orca population in the North Pacific.
How Orcas Hunt Their Prey
Orcas employ a diverse array of sophisticated hunting strategies that demonstrate high intelligence and social coordination. Fish-eating orcas often engage in cooperative techniques, such as carousel feeding. In this method, a pod herds a school of fish into a tight, dense ball near the water’s surface. The orcas then take turns slapping the ball of fish with their powerful tails to stun them before consumption.
Mammal-eating orcas rely on strategic silence and coordinated teamwork to overcome their prey’s defenses. A specialized method is wave washing, where a group of orcas swims in tight synchrony to create a powerful, unified wave that washes seals off ice floes. Other groups have learned intentional beaching, where they temporarily strand themselves on beaches to snatch seals or sea lions. This risky method is taught to younger whales by their mothers. These varied hunting skills underscore that the orca’s success as a predator is rooted in its social structure and capacity for cultural transmission.