Mouse question?

A mouse's tail can break off from being pinched in a cage door or a wheel. The tail was probably wounded, deprived of fresh blood, and then broke off. Also, some mice will chew themselves out of boredom. You can clean it with a q-tip and peroxide or Bactin. You may use the "liquid bandage" solutions sold for humans to seal the wound.

Here is a first aid website:

(broken link removed)

Based on our discussions, bubbleguine, I don't expect you'll be taking it to a vet. But just to let you know, it would be a good idea. Also, please check the cage for any dangerous objects that might have caused this injury.

If you have a wire wheel that could be the cause of it, you may want to invest in a solid plastic one.

We have a solid plastic wheel, no since it is at my sister college now

When had I some Gerbils the same thing happened to them, I just left it alone and it healed up fine. The mouse should be able to it clean enough, so long as the cage isn't dirty.