Guinea pigs are highly social animals whose welfare is significantly compromised by solitary housing, a practice still common in many countries.
Guinea pig welfare is well-understood relative to many small mammals, with clear scientific evidence that social companionship is a fundamental need rather than a preference. The Swiss legal requirement for companionship reflects this evidence base. Single guinea pig ownership condemns the animal to chronic loneliness that measurably impairs welfare. Companion matching requires care — introducing incompatible animals creates chronic conflict that is worse than brief supervised introductions through barriers. The welfare imperative is clear: guinea pigs should not be kept alone.