How can you tell the sexes of male and female raccoons?

The distance from the anus to the genitals is far greater in the male than the female. It is very hard to see the gender differences in baby rats, unless you can look at the whole litter. It is also hard to compare the baby rat to a grown rat.

The penis on the male is far away from the tail, close to the belly. There are no nipples on males. If you look closely where the fur stops, you can see two little lumps just below the fur. Baby boys will start to drop testicles at around three to four weeks of age. By four to five weeks of age, the testicles are obvious.

Notice on the female that you can clearly see nipples, which look like a series of dark colored dots. Nipples on baby rats appear at ten days or so old, before the rats are weaned. The female's vulva is very close to the tail. Some fur may appear to hang down a little from the genital area, but there are no lumps on the females like there are on the males.