Quote Originally Posted by satomi325 View Post
Females have nipples. Males do not. This is easily seen on their lower bellies.
Their genital to anal distance is also different. Females have a very short distance between the vaginal opening and anal opening. The male has a further distance between the penis and anus. Not to mention his scrotal sac will drop at around 4-5 weeks of age. So you could always just wait for that to happen before splitting the litter.


Around 3 weeks of age.
Female:


Male:


5 week olds
Female:


Male:


Those pictures are from this forum. It shows a pretty good guide of how to sex rats.
http://australianratforum.com/forum/...ustrated-Guide

http://www.ratz.co.uk/sexingrats.html

http://www.ratforum.com/showthread.p...xing-Baby-Rats
It is still rather disturbing to me how quickly you an post photos of rat's junk?

OP, once you get use to seeing them and a little confidence it will come easier.