mouse introduction

Question
Hi there,

I have a fancy mouse that I brought 6 months ago, I planned on putting her with my other mice but they didn't seem to get along together to well so I brought her a separate cage but keep them side by side so she was still social and she was happy and use to be happy to see you. A week and a half ago I brought another mouse like her ( this one is 6 weeks old and a girl apparently) because I thought she maybe lonely and want a buddy of her own, they had a bit of a tiff but then I've noticed she looks fat looking now, her hair is yucky and she just isn't herself at all, she breath quite fast too, and her bottom here looks dirty.  So I went out and brought another cage and clean them and separate her from the  new one, she has got on her wheel today and seem to pick up a bit but then she sleeps alot still she just seems very dull, do you think she will come right is there anything else I could be doing for her right now? She is eating and I've started giving her alot more veges and as of today she did get back on her wheel even if it was for a little while.

Answer
Dear Rachel,

It doesn't sound to me like a depressed mouse, it sounds to me like a sick  mouse.  The new mouse likely brought an illness with her from the pet store.

You'll probably want to treat both the new mouse and the other mouse with antibiotics.  

It is of course always safest to take the mouse to the vet.  Saying that, however, I know a vet visit can be cost-prohibitive.  

Of course many mouse owners are in the same situation, so I can send you to an archived answer where I explained how to treat a mouse at home.  This person's mouse had a more serious condition and had already tried one antibiotic, but the post describes how to administer a home remedy of the antibiotic Tetracycline, which you can get in the FISH section of the pet store.

http://en.allexperts.com/q/Mice-3824/2008/9/Administering-antibiotic-Tetracyclin...

Be very careful handling the different mice until these two have been treated, because you don't want to get the previous mice sick too.  

Now back to the companionship problem... I wonder if you are giving the mice enough leeway to get to know each other.  Mice do a lot of chasing and squeaking sometimes for a few weeks or more when they get to know each other. This is fine unless somebody gets a bite and is bleeding.  They have to establish rank.  The squeaking isn't pain, it's communication.

One way to help the introduction is to put the more aggressive mouse in a cage where the less aggressive one has been for 1-2 days.  Another way to reduce strife is to place a tiny dab of REAL vanilla on necks and tail bases (near their butt).  Maybe you can at least get down to two cages again!

best of luck with all the mousies.

squeaks n giggles,

Natasha