It is much easier to determine the sex of an older hamster that is accustomed to being handled than a wriggling baby hamster. Surprisingly, it is quite easy to see the teats on a female hamster when she is 6 or 7 days old and not fully furred, but once the fur grows and the baby is more active, it becomes harder.
Male hamsters of all species have a fur-covered gap between the penis and anus, whereas female hamsters have a smaller, baldish gap between their two openings (anal and reproductive). Chinese hamsters might be the easiest to sex, because even young males have a marked protuberance at the rear end.
Hamsters held in a curled hand with the head held above the thumb and the whole of the rear end hanging relatively loosely can be sexed fairly easily. The head of a dwarf hamster held in this way would be under the thumb. The thumb and index finger of the other hand can be used (very gently) to hold the hamster’s rear end still.
When sexing a hamster, you must hold it so that the rear end hangs down. This may sound disrespectful, but it is far better to get the sexing right than to put a male hamster into a cage of females hamsters or vice versa.
Some people advocate gripping the hamster by the back of the neck (called “scruffing”) for sexing. This method often fails, however, unless the scruff of the neck is gripped very firmly — and hamsters do not take this kindly. A scruffed hamster usually ends up wriggling so much that it is impossible to tell whether it is male or female hamster. Also, do not scuff your hamster if it has food in its cheek pouches.
Excerpt from the Popular Critters Series magabook Hamsters with permission from its publisher, BowTie magazines, a division of BowTie Inc. Purchase Hamsters here.