I'd be very careful with having both dogs not fixed...you could end up with doxie/boxer mixes, and mix breed pups can be hard to find homes for.
Medical problems and hormonal changes really can cause sudden behavioral changes, so I'd ask your vet about this. If your vet doesn't give it much thought, I would try to get in touch with a veterinary behaviorist because they would probably know about how health problems and hormonal changes can influence behavior.
It is very odd that they have been great together, but now they aren't anymore. I know many pairs of large and small dogs that get along very well, and so resolving the medical issue should help them get along better since they were getting along before. My black and tan dobie will become aggressive randomly when he has a UTI, which my family never expected to be the case. Medical problems can change behavior in very strange ways, that's for sure!
Medical problems and hormonal changes really can cause sudden behavioral changes, so I'd ask your vet about this. If your vet doesn't give it much thought, I would try to get in touch with a veterinary behaviorist because they would probably know about how health problems and hormonal changes can influence behavior.
It is very odd that they have been great together, but now they aren't anymore. I know many pairs of large and small dogs that get along very well, and so resolving the medical issue should help them get along better since they were getting along before. My black and tan dobie will become aggressive randomly when he has a UTI, which my family never expected to be the case. Medical problems can change behavior in very strange ways, that's for sure!
