While it is correct not to introduce 2 adult males, you could have presented him with a young male, provided the young one is between 4 and 6 weeks old. The young animal should be shampooed to remove odors of other animals and you would be as well shampooing both before introduction. Introduce them while they are both still damp. Cavies are less inclined to fight when drying off and should be used to each other by the time they have. Good food in the cage will also help to distract them.

However, the case is that you think the male has mated with your female. Indeed, females should not be bred after about 10 months unless she has already had a litter. When older sows are asked to breed, there is a possibility that her pelvic bone will have fused together causing a condition known as dystocia. This can be fatal for both mother and young. When a sow has a litter early in life, her bones never fuse – allowing her to reproduce past this 10 month barrier.

What I suggest you do is to take her to your vet and have him endeavor to see if her pelvic bones have fused together. I am not sure if it is possible to find this out. Your vet will be able to advise you further.