Q: I got two mice because I heard that they can get lonely, but what should I do if they express aggression toward each other? If I have to separate them because they are violent, then what’s the point of having two?
A: If your mice are not getting along, put them in separate cages immediately. Their safety and well-being are far more important than having a companion.
As a rule, mice are very social animals and can get lonely, especially females. I recommend that you keep two or more females together at all times. Female mice thrive on social interaction and established groups often welcome new members after a carefully monitored introduction. My groups of females usually have between four and eight members and it’s rare that they have any social problems.
However, I suspect you have male mice and they are a different story. Male mice are frequently territorial, and it is very unusual for them to live happily with a male companion. A female companion isn’t an option because of breeding concerns, so I recommend housing male mice alone. They live very comfortably like this and make use of any toys, houses or other enrichment you might add to their home. With a little extra attention from their human, male mice can have a rich and full life even though they live alone.