The blue whale is classified as a carnivore, despite its massive size and unusual filter feeding method. As the largest animal on Earth, this marine mammal requires a specialized and highly efficient strategy to consume the enormous volume of food needed to sustain its body mass. Filter feeding might seem passive, but it is an active form of predation on small animal life, classifying the blue whale scientifically as a type of carnivore.
The Specific Diet: What Blue Whales Eat
The blue whale’s diet consists almost exclusively of tiny, shrimp-like crustaceans known as krill. These small invertebrates form dense swarms in the ocean, which the whales actively seek out to maximize feeding efficiency during their feeding season.
An average-sized blue whale can consume an estimated 4 tons of krill every day, sometimes reaching up to 16 metric tons in concentrated feeding grounds near the poles. Sustaining this intake requires filtering up to 40 million individual krill daily. This intensive consumption is only possible because the whales target patches of krill where the density exceeds 100 krill per cubic meter.
How Filter Feeding Works
The blue whale employs a feeding technique called “lunge feeding,” which is unique to rorqual whales. The process begins with the whale accelerating toward a dense krill swarm with its mouth open. This rapid movement allows the whale to engulf an immense volume of water and prey, sometimes taking in up to 220 metric tons of water in a single gulp.
The whale’s anatomy facilitates this engulfment, utilizing specialized throat pleats, or rorqual folds, that expand like an accordion to accommodate the incoming water. Unlike toothed whales, the blue whale has hundreds of overlapping baleen plates that hang down from its upper jaw. These plates are made of keratin, the same protein found in human fingernails, and function like a sieve.
Once the water and prey are engulfed, the whale contracts its throat muscles and uses its massive tongue, which can weigh as much as an elephant, to push the water back out through the baleen plates. The fine, comb-like bristles of the baleen catch the krill, trapping the food inside the mouth. The whale then swallows the concentrated mass of captured crustaceans.
Why They Are Classified as Carnivores
The classification of the blue whale as a carnivore is based on the biological definition of its diet. A carnivore is defined as an animal whose diet consists mainly of animal tissue. Krill, the primary food source, are not plants; they are small, marine invertebrates classified as crustaceans.
Since the blue whale’s diet is overwhelmingly composed of these small animals, it meets the biological criteria for a carnivore. This distinguishes it from an herbivore, which eats plants, or an omnivore, which consumes both plants and animals. The method of consumption, while involving filtration, does not change the fact that the prey is animal life.