Guinea pigs in their natural environment are social creatures and obtain a lot of comfort and interaction from their other guinea pig friends.
Finding a friend for your guinea pig
Guinea pigs tend to be picky about their friends, and can be quite discriminatory.
Male guinea pigs who have grown up together or introduced carefully can get along very well, provided there are no females around, although it may be best to desex them to prevent fighting.
Female guinea pigs tend to be easy going but can be more aggressive if there are boys nearby or in the same enclosure. As with boys girl guinea pigs will be calmer and less hormonal if desexed. The best situation is usually a desexed male with two to three females.
How about rabbits, cats, dogs???
Guinea pigs are not ideal companions for rabbits as they have slightly different dietary requirements to rabbits, they eat slower, and tend to get beaten up by more dominant rabbits. In addition, rabbits can carry disease that is lethal to guinea pigs.
Guinea pigs rarely cohabit well with other species which in other circumstances would be predators. If you have indoor dogs and cats you do need a secure enclosure to protect your guinea pigs from becoming an accidental snack.