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 φαγειν, meaning "to eat".
The evolution of different feeding strategies 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 (carnivory), and later, plants (herbivory). Carnivory was a natural transition from insectivory for medium and large tetrapods, requiring minimal adaptation (in contrast, a complex set of adaptations was necessary for feeding on highly fibrous plant materials).
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 (including fingers in primates)
changes in body colour for facilitating camouflage, disguise, setting up traps for preys, etc.
changes in the digestive system, such as the system of stomachs of herbivores, commensalism and symbiosis
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.
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
Polyphagy 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 (see generalist and specialist species).
Another classification refers to the specific food animals specialize in eating, such as:
Carnivore: the eating of animals
Araneophagy: eating spiders
Avivore: eating birds
Durophagy: eating hard-shelled or exoskeleton bearing organisms
Haematophagy: eating blood
Insectivore: eating insects
Myrmecophagy: eating ants and/or termites
Invertivore: eating invertebrates
Keratophagy or Ceratophagy: eating horny material, such as wool by cloths moths, or snakes eating their own skin after ecdysis.
Lepidophagy: eating fish scales
Molluscivore: eating molluscs
Mucophagy: eating mucus
Ophiophagy: eating snakes
Oophagy: eating eggs (but also see "Intrauterine cannibalism" below), also Ovivore
Piscivore: eating fish
Anurophagy: eating frogs
Spongivore: eating sponges
Teuthophagore: eating mainly squid and other cephalopods
Vermivore: eating worms
Herbivore: the eating of plants
Exudativore: eating plant and/or insect exudates (gum, sap, lerp, etc.)
Gumivore: eating tree gum
Folivore: eating leaves
Florivore: eating flower tissue prior to seed coat formation
Frugivore: eating fruits
Graminivore: eating grasses
Granivore: eating seeds
Nectarivore: eating nectar
Palynivore: eating pollen
Xylophagy: eating wood
Omnivore: the eating of both plants, animals, fungi, bacteria etc. The term means "all-eater".
Fungivore: the eating of fungus
Bacterivore: the eating of bacteria
Planktivore: the eating of plankton
The eating of non-living or decaying matter:
Coprophagy: eating faeces
Detritivore: eating decomposing material
Geophagy: eating inorganic earth
Osteophagy: eating bones
Saprophagy: eating decaying organic matter
Scavenger: eating carrion
There are also several unusual feeding behaviours, either normal, opportunistic, or pathological, such as:
Cannibalism: feeding on members of the same species
Anthropophagy: the practice of eating human flesh
Intrauterine cannibalism
Oophagy or Ovophagy: the embryo/foetus eats sibling eggs
Embryophagy: the foetus eats sibling embryos
Filial cannibalism
Self-cannibalism: feeding on parts of one's own body (see also autophagy)
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.
Some animals exhibit hoarding and caching behaviours in which they store or hide food for later use.
Alcohol – 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.
