Sustaining the largest animals ever to inhabit Earth requires an immense and specialized diet. Whales, from the massive Blue whale to the predatory Orca, consume tons of food daily to power their colossal bodies and migratory journeys. The dramatic differences in diet are primarily determined by their anatomy, dividing them into two distinct suborders: the filter-feeding baleen whales and the hunting toothed whales. Understanding what they eat is fundamentally linked to their evolutionary success and global distribution.
The Diet of Filter Feeders (Baleen Whales)
Baleen whales, classified as Mysticeti, lack teeth and instead possess hundreds of keratinous plates in their mouths that act like a giant sieve. These plates, called baleen, hang from the upper jaw and allow the whales to filter huge volumes of water, trapping small prey inside. This group includes the largest species, such as the Blue whale, and they rely on high-density patches of prey to meet their enormous energy needs.
The diet of many large rorquals, including Blue and Fin whales, is heavily reliant on Antarctic krill, which are small crustaceans that can form dense swarms. A single North Pacific Blue whale can ingest an average of 16 tonnes of krill in a single day of feeding during the foraging season. This high-volume consumption of tiny organisms is necessary to fuel their long migrations across ocean basins.
Other baleen species focus on different zooplankton and smaller prey. The North Atlantic Right whale, for instance, primarily feeds on tiny organisms called copepods, which they skim from the water’s surface. Gray whales demonstrate a unique feeding habit by consuming amphipods and other invertebrates they suck up from the muddy ocean floor.
While often associated with plankton, many baleen whales also consume small schooling fish. Humpback and Minke whales frequently target species like herring, capelin, and sand lance, especially in northern latitudes where these fish aggregate in large schools.
The Diet of Hunters (Toothed Whales)
In stark contrast to their filter-feeding relatives, toothed whales, or Odontoceti, possess peg-like or conical teeth designed for grasping and tearing. This suborder includes the Sperm whale, Orca, and various dolphin species, and they pursue individual, often fast-moving prey. Their diet is far more varied and includes animals much larger than the typical fare of a baleen whale.
Sperm whales, the largest toothed predators, specialize in hunting deep-sea cephalopods. Their primary diet consists of large squid, including the Giant and Colossal squid, which they hunt in the dark, abyssal depths of the ocean. They also consume various deep-dwelling fish species, which they locate using highly developed biosonar over dives that can last more than an hour.
The Orca, or Killer whale, exhibits the most diverse diet of any cetacean, earning its reputation as an apex predator. Different populations, or ecotypes, specialize in specific prey, ranging from large schooling fish like Chinook salmon to marine mammals. Some transient Orcas target seals, sea lions, porpoises, and even other whale calves, showcasing complex predatory behavior.
Smaller toothed whales, such as Belugas and various dolphin species, consume a diet centered on smaller fish and invertebrates. Belugas feed on Arctic cod, salmon, shrimp, and crabs, often foraging near the seafloor. Common bottlenose dolphins primarily hunt smaller schooling fish, such as sardines and mackerel, alongside smaller squid species.
Specialized Feeding Techniques
The immense size and caloric demands of whales necessitate highly sophisticated and specialized techniques to capture their specific prey. These behaviors are often species-specific, reflecting millions of years of adaptation to maximize feeding efficiency in diverse marine environments.
The largest baleen whales, known as rorquals, employ a powerful technique called lunge feeding. A Blue or Fin whale rapidly accelerates toward a dense patch of krill with its mouth open, engulfing a volume of water and prey that can exceed the whale’s own body weight. They then use specialized throat pleats to expand their mouth cavity and expel the water through the baleen plates, trapping the food inside.
Other filter feeders use quieter methods, such as skimming, where Right whales swim slowly near the surface with their mouths open, continuously filtering plankton from the water column. Gray whales use suction feeding, rolling onto their sides to scoop up sediment from the ocean floor, filtering out benthic organisms like amphipods and worms. These differing styles are dictated by the density and location of their preferred food source.
Humpback whales are famous for their unique cooperative strategy known as bubble-net feeding. A group of whales swims beneath a school of fish and releases streams of bubbles in a circular pattern, creating a vertical “net” that corrals the prey into a dense ball near the surface. The whales then simultaneously lunge upward through the center of the bubble net to consume the concentrated fish.
Toothed whales rely heavily on advanced sensory tools and group tactics. Sperm whales use powerful echolocation clicks to locate squid in the dark depths and may even use intense sound to disorient or temporarily stun their deep-sea prey. Belugas also use their sonar capabilities to hunt fish in murky Arctic waters, relying on sound rather than sight for successful foraging.
Orcas, particularly those that hunt marine mammals, utilize highly coordinated pack hunting techniques that resemble terrestrial wolf packs. They can work together to create waves that wash seals off ice floes or take turns exhausting and isolating larger prey, such as a migrating Gray whale calf.