Regurgitation (digestion)

Flesh fly, from the Sarcophagidae family "blowing a bubble". One explanation for this behaviour is that it concentrates the fly's meal by evaporation. The diet of the flesh fly is very high in water content. The fly regurgitates the liquid portion of the food, holds it whilst evaporation reduces the water content and the fly then swallows a much more concentrated food meal without the water content. This continues until sufficient amount of liquid is left for the fly. - Australian Museum

Regurgitation is the expulsion of material from the mouth, pharynx, or esophagus, usually characterized by the presence of undigested food or blood.

Regurgitation is used by a number of species to feed their young. This is typically in circumstances where the young is at a fixed location and a parent must forage or hunt for food, especially under circumstances where the carriage of small prey would be subject to robbing by other predators or the whole prey is larger than can be carried to a den or nest. Some birds species also occasionally regurgitate pellets of indigestible matter such as bones and feathers. Penguins are known to regurgitate in order to feed their young ones.

It is in most animals a normal and voluntary process unlike the complex vomiting reflex in response to toxins.

In humans

In humans it can be voluntary or involuntary, the latter being due to a small number of disorders. Regurgitation of a person's meals following their ingestion is known as rumination syndrome, a rarely diagnosed eating disorder. It may be a symptom of gastroesophageal reflux disease (GERD).

A subset of people, most current or former bulimics, are able to regurgitate without using any external stimulation or drug, by means of muscle control. Practitioners of yoga have also been known to do this. Professional regurgitators perfect the ability to such a degree as being able to exploit it as entertainment.

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  Bubbling fly

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  bubbling fly (Calliphora vicina)

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  Pollenia sp. blowing bubbles (video, 3m 1s)