A domesticated rodent (family Caviidae) that originated in South America, where it is raised for food (it is not a pig and has no connection with Guinea). It does not occur in the wild. It is up to 25 cm long and weighs up to 1.2 kg. Guinea pigs live in small groups and feed on grass and practise coprophagy. They are widely kept as pets and have been used as model animals in scientific research since at least the seventeenth century.