When the female is in heat she will be more active than usual in many cases. (or so my observations are. This is not a rule) There are other ways to tell if she is in heat, but I think the easiest is to watch her activity level. Though, some animals are just very active all the time! You can also try gently, yet firmly stroking her back especially near her tail. If she is in heat she will 'freeze’ (back low slightly arched down and tail in the air. Eyes may or may not close) I have only had 2 females I've ever had do this for me, so I don't rely on this method. You can also just start trying to breed her. She will usually fight the male if she is not in season/heat. She may also just ignore him, but usally she will fight him.

To breed you will have to put the female in the male's cage or a neutral breeding cage. The male always goes in first. The female is much more territorial than the male and will fight and possibly kill him even if she is in season if you do it the other way around.

Always watch the pair carefully. Have leather gloves handy at all times. Fighting could break out at any second. If a fight breaks out use gloves and separate the two immediately! The gloves are to protect your hands when you separate the two. (You do not have to wear gloves, and I no longer do unless I know that one or the other is likely to be more vicious than usual. In most cases I try to get my hamsters friendly enough that once they feel my hand they will stop fighting.)

If the female is in season the male will mount her shortly. They will mate quickly and repeatedly in a short amount of time. After 30 minutes to an hour they will most likely loose interest and you should quickly separate them before fighting breaks out. Most of the time they will fight when they're finished. They may also just ignore each other when they're finished. The female should be put back in her own cage, or a cage specially prepared for her use during pregnancy and nursing. I just move her to her regular cage and then on the 12th day or so of pregnancy clean it and make it extra nice for the babies.

The female will not come back in season if she became pregnant. You can check to see if she is pregnant by putting her back in the male's cage or the breeding cage with the male. If she is pregnant she will fight the male and will not let the male mount her. (from my experience fighting breaks out very quickly. But again, they may just ignore each other) If she is friendly to him you can assume she wasn't pregnant after the first mating and let them mate again if you really want babies. I usually check in this manner every day for about 5 days just to be sure.

Throughout the pregnancy you should try to not handle the female at all. (some breeders disagree with this. I think it depends on your female. If she really enjoys being held you can hold her gently now and again. If she doesn't care either way I prefer to leave her be.) You will also want to provide more protein rich foods. Some foods she will especially enjoy are milk soaked bread, milk, nuts, some fresh vegetables and fruits and scrambled or hard-boiled eggs (small amounts of all these things!). You should not disturb her except for feeding her. Try to keep her away from noise if possible. The main thing to remember is to try to keep her as stress free as possible.

Around the 10th day of pregnancy she will most likely start showing pregnancy. On this day or the 12th day you should clean her cage, provide more than the usual shavings and more toilet paper than the usual amount. You should not disturb her again except to feed her. Even if you've been handling her from the 12th day on it begins to get a little more risky. Judge carefully on if you want to hold her or not.) On the 16th day of pregnancy she will most likely deliver (though it could be as long as the 18th day, it's usually the 16th day). It is best to leave her alone on this day and the few days around this.

Do not touch the babies at all! The mother will smell you on them and may kill, eat, or abandon the babies If the mother leaves the nest you may be able to see the babies.

There may be a few rare cases where the mother will abandon a baby even if you haven't touched them. Watch and see if she doesn't retrieve it with in half an hour and if it's still outside the nest rub a spoon in the shavings (preferably the 'toilet' corner) and gently scoop the baby into the spoon and set it beside the nest. The mother will likely go and take it straight back to her nest.

Here are some things to watch for until the wonderful day that you can touch the babies! Fur starts showing on back at day 5 (dark hair) and belly and paw fur (if white) shows up around 8-10 days. The babies start relieving themselves on their own day 8, eyes open day 10, and they are following the mother from open eyes to find out what to eat. Day 14 you can touch the babies (handle the mother too) and clean the cage! You can safely handle the babies at 14days of age. The cage may smell because there are so many little animals living in there. Do not clean the cage until the babies open their eyes. Keep the mother and babies together when you clean the cage so they will not act like strangers. When you decide to clean the cage either have another cage ready to put them in or use a large bucket. Something you can do before you clean the whole cage is you can clean out the urination corner daily or when it gets especially wet. You can then put clean shavings in to replace those.

The mother builds a nest to keep the babies warm and safe, and she can and does leave them for short times. This is perfectly normal! She leaves to eat, relive herself away from the nest, to get a drink, to stretch her legs. She shouldn't be handled as the smell from your hands will rub off on her then she will put this smell onto her babies which will confuse and stress the mother and she may harm her babies. The babies can be taken away from their mom at 18 to 21 days or later. Some breeders prefer to wait until the babies are 4 weeks old before they remove them from their mother. Usually if this is done the males are taken away a little earlier (like 3 weeks old). If you don't take them away from their mom the males will try and mate with her and the other females in the litter. Females are able to be bred at 21 days but you should never purposely breed her until she is 4 months old.

You can tell the males from the females by examining their body shape and genitalia. The males' testicles may start showing near the tail area giving him a more tapered look than a female at about 5 weeks old. If you turn them over you will see the gap between the anal and genital area is further apart in the males and closer together in the females, Also if you look on their undersides the females may have small dots showing where their nipples are.