Guinea pigs are highly social animals requiring companionship from their own species, with solitary housing causing significant welfare compromise through social isolation stress.
Guinea pigs kept alone experience chronic social deprivation that causes measurable physiological and behavioral stress. The social motivation of guinea pigs is high and cannot be substituted by human interaction or other species' company. Solitary housing is a recognized welfare compromise that the pet industry should address through paired sales and owner education. The cost of keeping two guinea pigs rather than one is modest compared to the welfare benefit. Introductions between guinea pigs can require patience and careful management but are almost always achievable and worthwhile.