Guinea pigs are highly social animals that suffer significantly when kept alone. In several European countries, including Switzerland and Austria, it is illegal to keep guinea pigs in solitary confinement.
Guinea pigs deprived of conspecific companionship experience social isolation as a significant stressor. They show reduced activity, reduced appetite, and increased fearfulness without social partners. Chronic isolation is associated with poorer immune function and shorter lifespan. Owners who keep a single guinea pig often inadvertently cause their pet significant suffering. Guinea pig companionship is not a luxury but a fundamental welfare requirement for this species.