Guinea pigs are highly social rodents who live in herds in the wild and suffer significantly when kept alone, yet single housing remains common in pet keeping due to underestimation of their social needs.
Guinea pig social housing is so fundamental to their welfare that Switzerland has made keeping them alone illegal — one of the few countries to legislate directly for the social needs of a companion animal. The sounds a single guinea pig makes — not the contented vocalizations of a socially satisfied animal but the quieter, more withdrawn profile of a lonely one — are difficult for inexperienced owners to distinguish from normal. A guinea pig with a companion is audibly different: more vocal, more active, more exploratory. Commercial cages sold for guinea pigs are typically inadequate in size for even one individual. The baseline welfare expectations of the typical purchased cage-and-starter-kit setup do not meet guinea pig needs.