Guinea pigs are highly social animals whose welfare is severely compromised by solitary housing, a practice that remains common despite strong scientific evidence for their social needs.
Guinea pig social needs are among the best-documented of any companion animal, and Switzerland took the remarkable step of making solitary housing illegal in recognition of this evidence. A guinea pig living alone experiences chronic social deprivation that causes physiological stress even when physical needs are met. Pairing or grouping guinea pigs requires compatible individuals — same-sex pairs are easiest to manage, and neutered male-female pairs work well — but the behavioral and physiological benefits of companionship are profound and consistent. Beyond sociality, guinea pig welfare commonly suffers from inadequate space, insufficient hay for dental health, and vitamin C deficiency from poor diet. These are all preventable with appropriate knowledge, suggesting that owner education is a high-leverage welfare intervention.