male mouse kills friend

Question
Hi. We had 2 male mice for close to 5 months. Our first was alone for a couple of weeks before we introduced it to another male. On occasion, we would notice their tails would be bleeding & we just thought the cats maybe got to them when the were close to the wall of the cage. We also have 2 male cats & 1 female cat in our home. The majority of the time the mice & cats are not in a room alone together. The mice are protected by a wired cage.
Last night when my daughter went to feed the mice, to her horror, she found her white male mouse, Mr. Jingles, bleeding at the neck & front foot area. His leg was completely pulled out of his body & what looked like maybe an intestine or something. He lay there with shallow breathing & looked as though he would take his last breath. The other mouse was under their "hut" just watching him. We are now wondering if the cat got a hold of his leg or is it possible the other mouse did this? Mr Jingles died within 20 minutes of us finding him like this.
If we were to ever get another mouse, how long should we wait & do you recommend a female next time? This upset my daughter as she was very close to her little furry friends. Any advice would be appreciated. Thank you.
Michelle

Answer
Dear Michelle,

I'm so sorry about Mr. Jingles.  Your pet store should never have let you think two males could get along.  Male mice almost never get along, and they do fight to the death.  

If you want more than one mouse at a time, you will need to get two or more females.  In any case your remaining male must live alone.  He will need extra love and attention from you because he will be lonely.  It's a sad fact of life for boy mice.

My condolences,

squeaks

Natasha