Like most other rodents, hamsters reach maturity quickly. That's why it's important to separate male and female hamster "pups" by the time they're 4 weeks old. Otherwise, you could end up with brothers and sisters mating and unwanted litters of baby hamsters. The age at maturity also varies by breed, with dwarf hamsters maturing later than the common Syrian hamster.
For the first two weeks of life, baby hamsters are dependent on their mothers for food and warmth. They are blind and their fur hasn't completely grown in. By the following week, they can see and look like small adults. In their fourth week, they are weaned and their mother starts driving them off. That's the time to take them out of the cage and separate them by gender.
By the age of 12 weeks, all types of hamsters are mature. However, Syrian hamsters mature by the age of 5 weeks. Because this species is so territorial, you must keep each hamster in a separate cage or there could be fights to the death. Dwarf hamsters can be housed in same-sex pairs, but keep a close eye on them after the 12-week mark. That's when some dwarf hamsters turn territorial, so you'll have to separate them.
Jane Meggitt has been a writer for more than 20 years. In addition to reporting for a major newspaper chain, she has been published in "Horse News," "Suburban Classic," "Hoof Beats," "Equine Journal" and other publications. She has a Bachelor of Arts in English from New York University and an Associate of Arts from the American Academy of Dramatics Arts, New York City.