Hamsters generally reach sexual maturity from 4 weeks old, meaning the male and female hamsters are able to mate and have babies. Therefore, it is important to start sexing baby hamsters and separate them by gender from 4 weeks onwards. Mating between siblings or between offsprings and parents is known as inbreeding and is strongly discouraged.
The following are two pictures to help hamster owners differentiate their hamster's gender:
Visible differences:
On the male, there is a significant distance between his male sexual organ and his anus. On the female, the distance between her sexual opening and anus is much shorter.
The male usually has a protruding rear due to the location of the testicles.
How to tell the sex of my hamster?