We are often asked about keeping rabbits and guinea pigs together. This is not advisable for the following reasons:
Bordetella bronchiseptica is a bacterial infection of the upper respiratory tract of a number of species, including dogs, rabbits and guinea pigs, related to B pertussis, which causes whooping cough in humans. It is often described as commensal in rabbits (ie found in this species without causing harm), however, it can be a primary disease causing organism, and can complicate other infections such as Pasteurella. It can, though, be fatal in guinea pigs, and so keeping them in the same airspace as rabbits is not advised.
Rabbits and Guinea pigs have different dietary requirements, particularly guinea pigs’ need for Vitamin C.
Rabbits and Guinea pigs are not the same species, and cannot respond appropriately to one another’s behaviours. This may result in inadequate social behaviours, up to and including severe bullying.
The main reason these species used to be kept together was for companionship without the risk of pregnancy. With improvements in anaesthetic safety and more widespread neutering of both species, this is less of a problem now. Whilst we would not recommend putting them together in the first place in this day and age, we would not advocate splitting up a stable sole rabbit:sole guinea pig pairing