What to do with wild mouse in winter

Question
I accidentally caught a wild mouse. It fell into a gift bag I had sitting around, and now I'm not sure what to do with it. It's smaller than I expected, so I'm not sure if it's an adult or not. I'd release it, but it's not exactly good weather outside. How can I tell if this is an adult mouse, and what should I feed it? I have the inclination to try and keep it as a pet, but I'm also concerned about disease and whether it would be happy as a pet. Please help!

Answer
Dear Sarah,

If the mouse seems happy in a cage (doesn't spend all its time trying to get out), you can keep it until it's warm enough to release it.  You won't want to handle it without gloves, so as long as you don't stick your face in its dirty cage litter, you're pretty safe when it comes to diseases (hantavirus, the main disease a wild mouse may carry, is transmitted through dried urine and feces, posing a health hazard for those who clean out old houses and barns).  

Other than food and water and bedding, it most definitely needs a wheel.  You can feed it a rat and mouse mix you get at a pet store. If they don't have something especially for rats and mice, a hamster mix is OK.  Supplementing the diet with fresh vegetables is appreciated but not absolutely necessary.  If it's too awkward to give it a water source, make sure it always has a fresh piece of cucumber or orange or other juicy fruit or vegetable in its cage at all times.  You can get a paper litter such as Carefresh for the cage, or use wood chips. Cut up cloth or paper towels or kleenex make nice cheap bedding materials (one of those stray socks will do just fine).

Once the low temps are above about 45 degrees, take the mouse about 1 1/2 miles or more away from your house, to a wooded or grassy area-- or it will come back!  It will appreciate it if you leave it a food supply.  

meanwhile, enjoy the little mouse!

squeaks n giggles,

Natasha