Fancy Mice Behaviour
Mice are very sociable and should ideally not be kept alone. Female mice, known as does must have company but male mice, known as bucks are much more difficult to keep together happily, even if littermates. Only experienced keepers of mice should attempt this.
Male mice can however be neutered, and if you have a vet with experience in this it is definitely worth considering. Neutered male mice will live together in small groups, or with females. You must wait 6 weeks after the operation before you can do this to avoid the risk of pregnancy.
For female mice, a trio works well since in the unhappy event of one dying, you are not left with a lonely mouse. Females like vertical space more than males, although both should have a large, barred cage and plenty of enrichment opportunities and hideouts. See the section on Fancy Mice Environment for more details. Male mice are said to bond better with their owners than females, but this will vary by mouse.
Mice are very curious but have quite poor vision, this does not affect them greatly since they rely a lot on their keen sense of smell. Blind mice have in fact been kept quite successfully and happily, and just require a little more thought in cage layouts.
Mice sometimes rattle their tails when angry or frightened, it is often territorial behaviour but can sometimes also be excitement or interest. Male mice also may shuffle their bum across a surface to scent mark.
It is natural for your mice to have a hierarchy, and sometimes you will find a mouse sleeping alone. Small squabbles, chasing and even same-sex mounting may occur and is normal behaviour. You only need to separate if blood has been drawn.
It is quite easy to introduce new female mice once you know how - in fact, a better group dynamic is achieved when you have a mixture of ages together. This can liven up the older mice, as well as giving the younger ones older animals to learn from. See the section on Introducing new mice for more details. Rodent intros vary quite widely so please do not apply this advice to any other rodent.