Guinea pigs are highly social animals whose welfare is severely compromised when kept alone or in inadequate housing.
Lone guinea pigs suffer significant psychological distress from isolation. Animals housed singly show abnormal behaviours and increased stress hormone levels. Inadequate space prevents normal ranging behaviour. Vitamin C deficiency causes scurvy with bleeding gums and joint pain. Dental disease from insufficient hay is common and painful. Many guinea pigs receive inadequate veterinary care with owners not recognising signs of illness.