Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, -vorous from Latin vorare, meaning "to devour", or -phage, -phagy, -phagous from Greek φαγεῖν, meaning "to eat".
Evolutionary history
The evolution of feeding is varied with some feeding strategies evolving several times in independent lineages. In terrestrial vertebrates, the earliest forms were large amphibious piscivores 400 million years ago. While amphibians continued to feed on fish and later insects, reptiles began exploring two new food types, other tetrapods, and later, plants. Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation.
Evolutionary adaptations
The specialization of organisms towards specific food sources is one of the major causes of evolution of form and function, such as:
mouth parts and teeth, such as in whales, vampire bats, leeches, mosquitos, predatory animals such as felines and fishes, etc.
distinct forms of beaks in birds, such as in hawks, woodpeckers, pelicans, hummingbirds, parrots, kingfishers, etc.
specialized claws and other appendages, for apprehending or killing
changes in body colour for facilitating camouflage, disguise, setting up traps for preys, etc.
There are many modes of feeding that animals exhibit, including:
Filter feeding: obtaining nutrients from particles suspended in water
Deposit feeding: obtaining nutrients from particles suspended in soil
Fluid feeding: obtaining nutrients by consuming other organisms' fluids
Bulk feeding: obtaining nutrients by eating all of an organism.
Ram feeding and suction feeding: ingesting prey via the fluids around it.
By mode of digestion
Extra-cellular digestion: excreting digesting enzymes and then reabsorbing the products
Myzocytosis: one cell pierces another using a feeding tube, and sucks out cytoplasm
Phagocytosis: engulfing food matter into living cells, where it is digested
By food type
is the ability of an animal to eat a variety of food, whereas monophagy is the intolerance of every food except of one specific type. Another classification refers to the specific food animals specialize in eating, such as:
* Self-cannibalism: feeding on parts of one's own body
* Sexual cannibalism: cannibalism after mating
Kleptoparasitism: stealing food from another animal
Lignophagia: eating wood, typically a pathological condition in some domestic animals
Paedophagy: eating young animals
Pica: appetite for largely non-nutritive substances, e.g. clay or hair, sometimes in pregnancy or in pathological states, typically a medical or veterinary concern.
Placentophagy: eating placenta
Trophallaxis: eating food regurgitated by another animal
Zoopharmacognosy: self-medication by eating plants, soils, and insects to treat and prevent disease.
An opportunistic feeder sustains itself from a number of different food sources, because the species is behaviourally sufficiently flexible.
Storage behaviours
Some animals exhibit hoarding and caching behaviours in which they store or hide food for later use.
Others
– it is widely believed that some animals eat rotting fruit for this to ferment and make them drunk, however, this has been refuted in the case of at least elephants.
