Rat pups

How old do the babys have to be to tell there sex? I had a litter 3 weeks ago and I fed one off *trying to find out what was a male and all look the same* as in females

Hold them under their arms and let them dangle. If you see testicles dangling, those are boys obviously :) Females have amuch shorter distance from the urethra to the anus.

I can tell at two days old.

females have a "bump" closer to the anus than the males.
Males will have a 'bump" about half way between their umbical scar and the anus. Like this.

http://www.afrma.org/sexing101.htm

THANKS ED!!!! Great link I have one male and a female I see the nipples so I'll grow the male up and feed him off and keep the female =] there so CUTE!!!