Mouse squeaks, skittish after partner dies

Question
Yesterday, one of our mice (Peppercorn) passed away just shy of being one year old.  She was in good health, and we don't know why she died. Her cage mate Steakbite was acting fine yesterday after peppercorn died.  Today, she acts very frightened, and will squeak very loudly when you pet her.  This is very out of character for her.  Is this stress from losing her partner; they have never been apart since birth, or should I take her to the vet?
She has since been placed together in a neutral cage with 2 other mice to keep her company.
Thanks for your advice,
Sean

Answer
Hi Sean,

Mice do grieve, and it's very possible she is just miserable after losing her buddy.  How is she doing with the other mice?  Give her a few days to adjust, and hopefully the new company will help her feel a little better.

To be on the safe side, check her all over (even if it has to be through the cage) for any possible injuries.  Look for weird bumps, small spots of missing fur, scabs, or red, irritated areas.  I don't think this is the issue, since she just lost her friend, but it would be wise to check just in case.

Hope she feels better soon
-Tam