How do you tell difference between mice and rats when a few days old

[SQ]

I have yet to see this baby, but how do you tell difference between mice and rats when a few days old?

Deer mice in NB do carry disease so I do not want to ask someone else to take that risk.
How can I tell if the baby is a very very young deer mouse or a rat or ... ?

pictures highlighting differences?

 

[Joanne]

If you can get some pics from different angles you could send it to mouseranch.com and see what they think.

 

[jorats]

Wouldn't mice be much much smaller?