Guinea pigs and rabbits have historically been housed together but this practice is now discouraged on welfare grounds.
Guinea pigs housed with rabbits are at risk of respiratory disease from bacteria rabbits carry asymptomatically. Physical injury from rabbit kicking, which can break guinea pig spines, is a serious welfare risk. Social incompatibility means guinea pigs in rabbit-only housing lack appropriate social bonding despite being present with another animal. The welfare harm from inappropriate interspecies housing is not always visible - the chronic stress of social incompatibility and the risk of bacterial disease cause harm without dramatic incident. The simple solution of housing guinea pigs with guinea pigs and rabbits with rabbits completely prevents these welfare harms.