Mouse species?

Question
Hi Natasha,

Don't know if you remember, but I had the mouse with the hole in her bum that ended up being a bot fly larvae. A lot has happened since I contacted you last. I might have to break this up into two separate follow-ups.

"Button", as I named her because she was just so cute, survived her parasite ordeal.  Her eyes were clear and bright and her fur turned thick and shiny.  I have to change my original guess to her being a house mouse.  She is a golden tan on top and white underneath with big eyes and ears.  Pictures of field mice/deer mice/white-footed mice look exactly like her.

I'm confused-is there a difference between these three species?

In October my cat caught a mouse in the basement which I promptly took away and put in a container to recover. This mouse was a bit smaller than Button but had the same coloring.  I did some research on sexing and compared the two, decided (with a prayer) the little one was a girl and thought I would keep her  so Button wouldn't be alone anymore.  I slowly, over a period of two days, introduced the two-always in a "neutral" container and separated by screen.  It was a success-they seeemed to take comfort from each other and the little one acted guite smitten!  So...now I have two-Smitten and Button.  

Fast foward-turns out I've got a mouse problem and have been going around sealing cracks and gaps in my house. Bought a couple different humane traps and have caught quite a few, all with the same appearance except for one, which was dark gray all over, small eyes and smaller ears-
I'm assuming this was a house mouse?

I made little shelters for the caught mice and have been taken them to parks with lots of trees and brush and leaving piles of seeds and nuts around each shelter. This might seem extreme to some people, but I feel bad about having to turn them loose and want to give them the best chance at survival I can.

Don't know where I'm at in my character limit so I'll just finish with another follow-up.  I've got a dilema I need your help with.

Thanks for your patience, Trissa

Answer
Hi again!

How wonderful that Button made it. I had little help for her, considering this thing had been eating her flesh since she was a few days old. What an amazing little girl.

"Field mouse" is a catch-all term for an outdoor mouse. There is a deer mouse and a white-footed (deer) mouse. Deer mice have longer tails. Here is a description of all three:

http://www.thefunmouse.com/info/species.cfm

This site will also tell you how to tell boys from girls:

http://www.thefunmouse.com/info/sexing.cfm

You can see their undersides in a glass dish or aquarium.

Thank you for being so nice to the mice you have caught. These parks are more than a mile from your home I hope.

Will follow up in your follow-up

squeaks,

Natasha