Bitten off ear

Question
I have had 7 female mice in a cage together for over 6 months. I clean their cage once every 2 weeks and today discovered that one of the smaller mice had had her ear completely bitten off. You can look right down the ear canal into her head. I put her in a seperate cage with clean bedding and only one other mouse (the other smaller one). I have searched all over online, and have found no answers, I am very worried. I put peroxide and bactracin on her ear the best I could but she seemed to just be grooming it off. Is it okay to put them all back together, or should I keep them seperated until her open sore heals completely?

Answer
Dear Haley,

For me it comes down to:  Are they fighting?  and, Is the first time blood has been drawn?  When mice draw blood, it pretty much means that they will never live together well.  However with 7 mice, it might have been an aberration.  

Wait a few days until the mouse is feeling better and then put them back together.  But if blood is drawn again, they must be kept apart.  

Good luck!

Squeaks,

Natasha