Many books, the majority of vets, most pet shops and the major animal charity in this country advise that guinea pigs and rabbits can be housed together. NO, NO, NO!. This can be hazardous for both species.
I recently read an article by a national newspaper's tame vet in which he advised just such a practice and jokingly said that there was nothing to worry about if the rabbit got over amorous. Having seen the kind of injuries that can be caused by what this man thought was a 'Jolly jape' I seethed with anger at such utter stupidity and thoughtlessness. However, the main danger comes from something far more common in rabbit behaviour,
I always maintain that you can tell a rabbit breeder by the scratches down the inside of his or her arms. They are usually caused by the powerful back legs of rabbits which kick back when they are being lowered down into the quarters. Rabbits can do this kicking back action at anytime when they are moving about their quarters and guinea pigs are a darn sight frailer than human arms.
From the rabbit's point of view the danger is in the dietary needs of the guinea pig which is high green vegetable matter. Try making the same amount a guinea pig needs, available to a rabbit and you are going to end up with a rabbit with a runny backside. You could of course tell the rabbit that the measly bit of apple or carrot is for him while all that lush green is for the guinea pig but I don't think it would listen!.
Every breeder, rabbit sanctuary and the major rabbit fancy in this country feels the same way about mixing these species. One day, perhaps, the veterinary profession and most pet shops will listen to those who know these animals and their needs!.
Of course many of these animals have lived together without mishap but there are far more that have ended in disaster, mainly for the guinea pig.