The basic differences are similar for all species of hamsters, Syrian, dwarf, or Chinese.
Hold your hamster on its back to look at the belly area. You can cup your hand over your hamster and gently turn it over onto its back, or hold the hamster by the scruff. Holding the hamster in a slightly upright ("sitting up") position will help you determine if testicles are present.
Anogenital Distance
The surest way to tell is by looking at the anogenital distance. This is the distance between the genital openings (penile opening in the male, vaginal and urinary openings in the female) and the anus. This distance is much shorter in females than males (in fact the openings can be difficult to distinguish in females while they are separated by about half an inch in males). This is illustrated in the diagram above.
Other Differences
- The back end of the male tends to be elongated and rounder in appearance in comparison to the female (especially noticeable in Chinese hamsters).
- Males often have a noticeable scrotum with testicles after about 4 weeks of age, although the testicles can be retracted.
- Only females have nipples
More Help Sexing Hamsters:
- Sexing Hamsters on the Pet Web Site
- Sexing Dwarf Hamsters, Part 1 - YouTube video from Animal Lovers Web; unfortunately not quite in focus during the critical bits, but you can still see enough to appreciate the differences.