The sex of adult hamsters is easy to determine. Males have very large, prominent testicles. In fact, owners unaccustomed to seeing them are often astonished at these anatomic peculiarities.
Male golden hamsters should be first bred when they are 14 weeks old. Females should be first bred when they are 10 weeks old. As the time of copulation approaches, thin, stringy, cobweb-like mucus exits the female's vulva.
The female is then placed into the male's cage about one hour before dark. The pair must then be carefully observed for mating activity and/or fighting. Females can be very aggressive to males in this situation and can harm them.
The male should be removed at once if there is fighting. Because fighting is so likely, aggressive males are best hand-mated. In these situations, they are better able to defend themselves and "hold their ground." The male should be removed after mating.
Pregnancy lasts only 15 1/2-16 days. Before delivery, the female becomes restless and usually discharges a small amount of blood from her vulva. Litters usually range from 5 to 10 pups. The ups are born hairless, with ears and eyes closed. They do, however, have their front teeth (the incisors) at birth.
Female hamsters with young must be provided with abundant nesting and bedding materials, and plenty of food and water. They must not be disturbed in any way.
The young should not be touched or handled until they are at least 7 days old, the nest should not be disturbed, and the cage should not be cleaned during this period.
Failure to heed these cautions (especially with females nursing their first litters) most often results in cannibalism of the young. Observant owners may note an interesting maternal rearing activity, especially if the female with young is excited or disturbed. She will stuff pups into her cheek pouches and deposit them into the nest a short time later when she believes the danger has passed. Occasionally, pups suffocate as a result of this activity, especially during lengthy periods of disturbance.
Young hamsters usually begin eating solid food at 10 days of age but are usually weaned at about 3 weeks of age. Solid, pelleted food must be soaked to soften it and be placed on or near floor level of the enclosure for easy access by the weanlings.
As mentioned above, sipper tubes must be positioned low enough so that the smallest pups can reach them. Some pups will not be strong enough to extract water from sipper tubes, so owners must be vigilant for this potential problem and provide an alternative water source for them.