Mouse left behind

Question
I was a charity benefit last night where they had a mouse race, after the person who was running it left we found a little black mouse and someone said it was from the races and must have gotten out. We caught it and I brought it home but now I wonder if it is a wild mouse. It is acting quite content in it's cage, not trying to jump out and it's not getting freaked out by my presence even when I put my hand in the cage and touched him and once we caught it he calmed down when I put him next to my body and petted him a bit, but it seems a little small for a pet mouse. Do you have any experience in this?
I don't want to bring in a wild mouse and possibly get sick.

Answer
Dear Sarah,

It is just either a young one or a runt. Are you going to keep it as a pet?

If it is a female it needs girlfriends. If it is a male, it lives alone. Males are pretty obvious- they have quite a sac behind. Compare:

http://www.thefunmouse.com/info/sexing.cfm

That site is also an excellent one for all the information you need about mice!

Enjoy the new world of mice...

Squeaks n giggles,

Natasha