My mouse keeps picking on the new mouse...

Question
Hi,

I recently bought a new mouse for my two girls (This one is a girl aswell.) and the oldest mouse, Pichu, keeps attacking the little one (Peanut). I understand that Pichu is only being the dominating female because it was her territory first, but when i got my second mouse, she was never this aggressive.
I was just wondering what some ideas would be to help stop Pichu picking on Peanut.

Thank you =]

Answer
Hi Sophie,

For the first few days, a little chasing and bossing is normal, but if you notice any violence it becomes much more serious.  How is she attacking her?  Do you see any biting, or does Peanut have any scabs beneath her fur if you blow backwards on it?  Do either of them show any strongly defensive behaviors like tail rattling (vibrating it against something in the cage so it "buzzes") or boxing (standing up on the back legs and punching out at the other)?  These are all signs that not only are they not getting along, but they should be separated to prevent real injuries.

If Pichu is just chasing her a lot, taking her food, etc., there are certainly things we can try to calm them down a bit.  First, make sure that there are ample supplies in the cage - never let them run out of food or water, and when giving them treats, be sure to give them each their own.  Second, if Pichu is guarding certain areas, try and remove anything they could fight over, such as extra toys or hides.  Changing the bedding can also help, as the cage likely smells like Pichu only.  Another good thing to try is to put a tiny, itty bitty dab of vanilla extract (real only - substitute does NOT work) under each mouse's chin and just over their tails.  This makes them both smell the same, and may give them enough of a break to settle things out.  If nothing seems to help, please write me back and we'll explore some other options.

Of course, until they establish who is the boss, scuffling may continue, but as I mentioned it should only last a few days.  Again, if you spot any violence, please separate them immediately.  It's not worth anyone getting hurt.

Best of luck, and congratulations on your new mouse!  Let me know if there's anything else I can help with.

-Tam