Mouse becomes aggressive after cage change

Question
Hi, I need some help, I have 3 pet mice, all girls and have had them for about 4 months or so, Snap, Crackle & Pop. Crackle is quite a bit smaller than the other two (i assume that she was the runt of the litter as she has always been much smaller) they have never really been a problem before, but about a week ago I got a new tank for them, as I wanted them to have more space so it is quite a bit bigger. Over the last few days Pop (who is the biggest of the three) has been chasing crackle an awful lot, she pushes her into the corner and makes her squeak, but they were still sleeping together. This morning when i woke up Pop was again chasing Crackle around and making her squeak, but this time i noticed that she was biting her on her back/rear end (there are no obvious wounds or blood), this has continued all day, and now she has started doing it to Snap too, who is not that much smaller than herself. i looked up about it before and just came to the conclusion that it was a dominance/ hierarchy thing, but im really starting to worry now, Pop will not let the other two into the bed, and when they go in there, there is a lot of squeaking, then she pushes them out. I dont want to have to seperate them, but i dont know why she is doing this, or what to do, everywhere onling just says to leave them as long as they are not drawing blood but they all seem a little bit fed up & i feel very fed up too.

Thanks in advance for your help

Kelly

Answer
Dear Kelly,

One of the conditions that I give to tell when you have to separate mice is if someone cannot access the nest. The cage change gave the mice enough space for Pop to become territorial. You either need to separate them or put them back in the smaller cage- and the problem might not even be solved by putting them back, since this has developed. Probably what you will want to do is take Pop out and put her in the old cage. If you want to try a new friend for her, get a wee baby and follow the usual instructions (spotless cage, no toys except wheel, REAL vanilla on their necks and rumps). If it doesn't work the new girl can always go in the other cage. You must keep the cages close so they can still communicate. And remember, Pop is simply being a mouse as best she knows how and following mouse rules. She is not a naughty mouse and will need even more love- an hour a day- if she has to live alone.

Best of luck. Let me know what happens.

Squeaks,

Natasha