Your heart is in the right place but you need to release it, you dont know what kind of diseases it may be carrying. I saw a hawk take a chickadee by my bird feeder the other day and I almost cried. It is the circle of life as you said.
Christine

Actually I had seen this exact question asked on a website selling humane mousetraps and this was the lengthy answer provided by PETA:

"PETA: Thank you for your post about humane trapping during cold weather! Rodents do not hibernate during the winter, so ideally all holes/cracks in buildings and foundations should be sealed and rodents should be live-trapped and released before cold weather arrives. The animals in your aquariums can be "soft released" during mild weather. To do this, make a temporary home out of a sealed plastic or wood container that has a tiny doorway and an adequate air supply (add air holes, if necessary). Thoroughly insulate the container with straw, newspaper shreds, cotton, or fleece. Place the container 100 to 200 yards from where the animals were trapped, preferably in a wooded area, and conceal it with branches, leaves, and other organic matter to provide additional protection from poor weather and predators. Provide the mice with at least a week's worth of high calorie foods such as peanut butter, dry cat food, and/or wild bird suet. Release the mice inside this temporary home. If the weather is very cold, live traps should be disabled. "

What I probably would do is get an old small box and throw in some old towels, fabric, etc and a couple of crackers, making sure there is a way for the mouse to get out. Leave it far from your house (and anyone elseâÂÂs) and hope for the best, at least it has a fair chance. But then, I'm nuts too ;-)

Some people mention that they put the mice they capture during the winter in an aquarium, but I wonder doesn't that give the mice more opportunity to reproduce. Now that seems a little strange to me...

Thanks for the reply. I can handle releasing them that way. Wish I knew what 100 to 200 yards is when eyeballed. I don't have a car so I'll have to plan my release by weather which is good for the mouse too. I bought some trail mix and I have cat food but not dry stuff. I can grab some since I'll probably have to do this a few times. I'll look into some cheap boxes from the dollar store to release them. I have no plans on keeping this thing as a pet or caring for it because I know they are disease ridden vermin but the thought of dropping it in the middle of a snow pile is just too cruel :( I'll feel much better taking this approach and knowing it has a chance. I just wish my cat would do what cats are supposed to do! Lazy lout!

I once live captured and released mice. We used an aquarium with a thick layer of shavings on the bottom, hung a water bottle on one side and dropped their food into one corner of the container. They tended to burrow into the shavings so when we released them we just laid the container on it's side under a bush and covered it with leaves branches, etc. Leaving the aquarium wasn't ideal but I did go back at a later date and retrieved the aquarium. I don't know if I'd trust keeping them in anything other than plastic or glass.........cardboard they could chew right through.

Oh, and we did keep them several weeks.....no breeding or babies. Surprisingly, we didn't see any more mice after that.