Trophallaxis
From Wikipedia, the free encyclopedia
Trophallaxis is the regurgitation of food by one animal for another. It is most highly developed in social insects such as the ants, in which individual colony members store food in their crops and regularly exchange it with other colony members and larvae to form a sort of "communal stomach" for the hive. It is also used by some vertebrates, such as birds feeding their young.
Trophallaxis is also performed by members of the dog family. In the wild, a hunting dog will regurgitate food gorged while far from its lair in order to feed its puppies. These puppies lick the face of the adult in order to trigger trophallaxis. Domestic dogs are tame because of arrested development of their wild tendencies and will treat certain humans, in particular their owner, as lifelong 'parents'. Therefore, when a dog licks your face, it may be that he's manifesting a vestigial feeding instinct.
However, it's also true that many dog owners like to put their face close to a dog's face to get "kisses." This is actually experienced by the dog, on an instinctive level, as an act of aggression, which may trigger a momentary impulse to bite the owner. In such a case, licking the owner's face may be a sublimation of the urge to bite. In either case, the licking creates strong positive emotions in the dog and the behavior is reinforced as a result.
Trophallaxis serves as a means of communication, at least in bees and Ants
