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. (October 2017)
Circular dendrogram of feeding behaviours
drinking blood (hematophagy
) from a human (note the droplet of plasma being expelled as a waste)
Feeding is the process by which organisms, typically animals, obtain food. Terminology often uses either the suffixes -vore, -vory, or -vorous from Latin vorare, meaning "to devour", or -phage, -phagy, or -phagous from Greek φαγεῖν (phagein), meaning "to eat".
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 (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
By mode of ingestion
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
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
- Herbivore: the eating of plants
- Omnivore: the eating of both plants, animals, fungi, bacteria etc. The term means "all-eater".
- By amount of meat in diet
- Fungivore: the eating of fungus
- Bacterivore: the eating of bacteria
The eating of non-living or decaying matter:
There are also several unusual feeding behaviours, either normal, opportunistic, or pathological, such as:
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.