Guinea pigs are highly social animals whose welfare is often compromised by solitary keeping and inadequate housing.
Solitary guinea pigs suffer from loneliness and are prone to depression and anxiety. They need same-sex companions or appropriately matched pairs. Inadequate space prevents natural behaviors like foraging, exploration, and play. Vitamin C deficiency is common and serious. Many guinea pigs in pet shops are housed in conditions that would be illegal in several European countries.