The blue whale is a filter feeder, consuming a diet composed almost entirely of krill.
Mass feeding is one of the five feeding strategies that animals use to obtain food. Mass feeding is shown when animals eat pieces of other organisms or swallow them whole. Other feeding strategies include filter feeding (employed by a variety of marine organisms, from krill to blue whales), reservoir feeding (earthworms and other animals that filter or gather from the ground), fluid feeding (hummingbirds, which feed on nectar, or spiders, which suck the entrails of insects) and phagocytosis (used by protozoa to engulf food particles).
Mass feeding is one of the most common feeding strategies among animals, especially among the macroscopic animals with which we are most familiar. Many herbivores, carnivores, and omnivores use mass feeding. Except for a few cetaceans (whales and relatives) that use filter feeding, almost all organisms larger than a few centimeters feed en masse, including humans. It’s one of the most efficient forms of feeding, especially on land: it involves going straight to the food source and taking a big bite, then repeating until you’re full.
A nonbulky feeder would be organisms such as millipedes, which feed on deposits, and various scavengers on land and in the sea, which eat detritus rather than parts of living or recently dead organisms. Some bulk-feeding animals, such as cows, specialize in eating plants and have large, barrel-shaped stomachs to break down hard-to-digest grass. Others, like cats and canids, are specialized carnivores, evolved to hunt living organisms, kill them, and consume the fresh meat. Among the most flexible organisms, omnivores, like humans, use both strategies.
Among the largest mass eaters in history, sauropods, huge dinosaurs that lived during the Mesozoic era, consumed tons of plant matter daily to maintain their sheer bulk. One sauropod, Brachiosaurus, weighed between 30 and 60 tons. These animals had large stones in their bellies, called gastroliths, to break down plant matter and release its nutrients for further digestion.