Hand raising a field mouse

Question
I found a baby field mouse in my garden a week ago, it's eyes were still closed and it was getting swarmed by ants, so I couldnt leave him alone (assuming he is a boy as he has a prominent thing sticking out under his tail!).  I looked around for a nest, but had no luck so brought him inside.  I was feeding him kitten formula and it a couple of days ago he opened his eyes and has now stared eating mouse food and seems to be doing very well, although still very tiny.  I have been doing research and get alot of different opinions on what to do with him, and am therefore a little confused.  Some say let him go after 4 weeks(when weaned) and some say keep him as he will not survive.  He has become quite tame, but is quite jumpy.  If the best thing is to keep him, should I get another mouse to keep him company or will be be ok on his own? (if he is a boy, I dont really want to get a female and have lots of babies).
Your advice would be gratefully received.
Many thanks

Answer
Dear Karen,

It's great that you have been able to keep the little one alive.  The kitten formula is perfect.  Do some back research in  my answered questions for help on raising it as well.

The mouse is not going to be able to survive well on its own.  It's been sick and so it is weak.  Mice are created to survive as a species by there being a lot of mice so that when many get eaten, a few survive; thus, a single mouse is very vulnerable in the best case scenario, let alone one with compromised health and rearing.  

Although mice are happiest with a pal, in your case it isn't feasible for several reasons.  First, if it's a boy, you can't put it with another boy because they will fight- so half of all mice have to live alone!  Second, you don't want to put a boy with a girl or vice versa, of course.  Girls live together well most of the time, but you can't mix wild mice with pet mice; and even if you were to decide to catch a wild friend for it-- which I highly discourage because mice brought up in the wild are happier there-- the problem is that a healthy mouse would likely attack this one.

Thus if you can keep it as a pet, it's the best bet for the mouse.  You have a few weeks to make up your mind, though, because you don't want to let it go in the cold weather or before it is 2 months old anyway. If it is tame it will love you and enjoy living with you.  One thing is it MUST have a wheel or it will go stir crazy.  As for the jumpiness, you just need to hold onto its tail gently with one hand while the mouse sits on the other.  It will get less jumpy if you handle it often.  

By the way, female genitals look a lot like what you would think a male looked like.  The two ways to tell are 1) only females have nipples (4 rows), and 2) when males get older their testes make it look like they have big buttocks.  

Have fun with the little thing!

squeaks n giggles,

Natasha