Is my mouse just getting old or sickly?

Question
Hello Tamarah

I bought two female fancy mice last year in August a few months back I had to separate them due to barbering issues. After the separation one of the girls was chirping alot and acted lonely she is closely bonded with my mom so we put my moms socks with her scent on them in her cage. Since then she hasn't chirped but about a month ago she started up the chirping and I noticed red discharge from her nose I was worried she might have gotten sick. She was eating and drinking normally and has always been low energy. I took her to the vet and got her on some antibiotics and finished them. Well tonight I went to take her out for play time and she felt really cold. I thought this might be that she is older and cant regulate body heat as well. I put shredded tissues in there, strips of warm fabric, and a stuffed animal to help her warm up. Its been a few hours and I checked on her she still seems a bit cold. She still seems to be eating and drinking normal but should I worry something else is going on?
Also do you think I could try to put them back together and see if they can get along now?

Answer
Hi Nikki,

I'm sorry I didn't see this sooner - I hope she's alright!  I thought about this pretty hard, actually, and I don't think it's a good idea to put them back together.  While doing so would keep her warmer, it could also stress her (because reintroducing females usually causes a day or two of chasing and skirmishing), which could lower her immune system.  I'm also not sure who barbered who, but if she was the one losing fur, that could have poor consequences.  Lastly, if it is due to an illness, she could pass it on to the healthy girl, which wouldn't be good at all.

While it's hard to say what is causing her to get so cold, it's clear that you should try and get her body temperature back up.  Being cold makes her more susceptible to illness, which in turn can cause her to get colder.  You can help her out by adding extra bedding, placing her in a warm part of the house, putting a heating pad on its very lowest setting under half of her cage, or even by adding foods with extra protein to her diet.  Good foods to try are dry cat food, dog biscuits, mealworms (you can find them at your local pet store), and scrambled eggs made without milk, or with kitten milk replacement for even more protein and nutrients.  The more nutrients she can take in, the stronger her immune system will be and the warmer she will stay.

Once you've helped with her chill, it's time to consider the cause.  If you bought her in August of last year, she's probably about a year and a half old.  Mice typically live anywhere from 1-3 years, the average being about a year and a half to two years old.  Unfortunately, it's not always possible to predict these things, as mice with unknown backgrounds are genetically a roll of the dice.  Some are extremely healthy and resilient, while others might be more prone to sickness than others.  In short - she might be slowing down with age, but considering her recent respiratory illness I would look to that first.  Did her chirping cease with the first round of antibiotics?  It's possible it didn't fully respond to the first kind of medicine, or that something else has moved in to cause a problem.  In either case, a round of a different type of antibiotic couldn't hurt and may turn it around.

Hope she's doing okay, and best of luck!
-Tam