Guinea pigs are highly social animals that live in groups in the wild. Keeping a single guinea pig without a companion causes chronic social stress, loneliness, and welfare compromise. Norway has made single-kept guinea pigs illegal.
Guinea pigs vocally call to companions and show distress behaviours when housed alone. Social grooming, play, and companionship behaviours occupy significant portions of a guinea pig day in group housing. Isolation removes these entirely. The welfare cost of single housing is well-evidenced and preventable. The UK has no equivalent to Norway legislation preventing isolation, meaning millions of guinea pigs are kept suboptimally.