found a wild baby rat

Question
Hi.  Last week we found a dead female rat in my backyard.  It appeared as though she may have been a nursing mom.  I am not quite sure why she died because she looked very healthy and had no trauma on her.  Needless to say yesterday there was a cute little rat on my back porch.  I am not sure how old he or she is. But he is going to the bathroom on his own and I can see that he already has teeth.  I offered him some rat food and although very interested I don't think that he is quite able to eat it yet. Yesterday I feed him regular milk through a very small syringe.  I just put the tip by his mouth and he will kind of lap it up.  Today I found a recipe to make formula for puppies and have been giving it to him.  He seems to love it better than the regular milk.  I also bought multivitamin drops for rats and added it to the formula.  He is very sweet and gentle. If I put my hand in the box he will crawl right up my arm and nuzzle himself in to me. I would really like to keep him.  Is that possible, considering that he is a "wild" rat?  I have had pet rats and mice in the past and really enjoy them.  Do I need to be concerned about diseases?  Also is there a way to figure out how old he is?  Are there any other things I should be doing for him?  Thank you so much for your help.

Answer
You can keep him, and if he is clean (as it is the fleas on the rats that caused disease) there should be no trouble. Rats are born with teeth, I would guess he/she is probably 5-8 weeks.  If it is a boy you will see testes, if a girl you should see nipples.  Do you have a camera?

Well done on saving this little guy.  I would have done the exact same thing!!  :-)