Is my white mouse male or female?

Question
I caught a white mouse here in Michigan Labor Day weekend 2007. I saw it for about a month and it was coming to my critter feeder and I know in this state that white mice aren't wild. It took a bit for it to warm up to me but is now my favorite little friend.  I just don't know how to tell if I have a little girl or boy.  How do I tell?

Answer
You are right, the only white 'wild' mice are ones who have escaped as white mice would be easily spotted by predators. Well done catching him!

It is most likely a fully grown adult. On males you will notice some extra skin between the anus and the genitals. In a relaxed state you will see two testicles just under an inch in size.

Another indicator is the smell. All mice smell but males smell far worse, most people find it offensive. They use it to mark their territory and attract females.

If you have a female have a look at her tummy and you may notice 10-12 tiny nipples. These are trickier to see in lighter colored mice.

These are the easiest ways to tell. If you are still having trouble you could send me a picture of their genitalia or I could give you further methods (though trickier) of deciphering whether it's a male or a female.

Please feel free to ask any more questions, good luck.