Breeding Mice - The Basics

Sexing Mouse Young

One of the most important and frequently asked questions a new mouse breeder asks is: "How do I tell the sexes of my mouse babies apart?". Sexing can be rather tricky, especially at first when one doesn't as yet know exactly what to look for. Fortunately, sexing mice gets easier with practice.

How easy or difficult sexing is, depends on the age of the young. Very young, still hairless babies are somewhat easier to sex than older ones, but by the time the males should be separated from the females, sexing is again easier. Long hair and curly coated young may be more difficult to sex, as their coats tend to hide their 'parts'. Young male mice can hide their testicles when they are nervous, but they will let them drop again after they relax a bit.

Pictures can tell more than a whole bunch of words, so below you can find pictures of both female and male mice of different ages.

Does (females)	Bucks (males)
Look for teats. Females have them, males do not. The small genital opening ("tab") of females is smaller than on the males and closer to the anus.	Male mice do not have teats. Their genital opening is larger than on females, the distance between anus and the genital tab is longer and the tab is pointed towards the tail.