Guinea pigs are highly social animals whose welfare depends critically on companionship. Solitary housing causes chronic stress, and many countries now legally require guinea pigs to be kept in pairs or groups.
The social nature of guinea pigs makes companionship a fundamental welfare need rather than an optional extra. Research consistently shows that isolated guinea pigs exhibit behavioral and physiological markers of chronic stress. The legal requirement for pair housing in multiple European countries reflects the scientific consensus. Welfare assessment should always include evaluation of social group composition, space adequacy, and quality of social interactions including allogrooming and proximity seeking.