This can have several causes, too much or decaying vegetables or fruit, a sudden change of diet, stress or infection from another hamster with diarrhoea. A hamster with diarrhoea will have soft droppings, may be soiled underneath and may have an unkempt coat. Ideally the hamster should have only water for 24 hours then a diet of hamster mix only until the droppings have hardened. Never give milk or fatty foods to a hamster with diarrhoea or it will make the problem worse. If the condition doesn't clear up within a few days or the hamster looks poorly take him to a Vet. There is an extremely contagious disease which affects hamsters which is commonly referred to as wet tail. The symptoms of this are very severe diarrhoea and the hamster will appear wet and dirty all round the rear end. There will often be an unpleasant smell from the hamster and cage. This disease is often fatal and veterinary advice should be sought straight away. The hamster should be isolated from any others.
This is a dominant gene in both the Syrian hamster and the Chinese hamster. In the Syrian hamster crossing two dominant spotted hamsters produces two thirds of the litter dominant spotted offspring and one third non spotted, instead of the normal expectation of three quarters of the litter showing the dominant characteristic and one quarter the normal non spotted version. This is because the dominant spotted gene is a dominant lethal with 'pure' dominant offspring not being born. This therefore reduces the proportions to those shown above as the quarter that would have been pure dominant spots do not appear.
The world is a dangerous place if you are as small as a hamster, therefore you need to keep his surroundings safe. Always keep larger animals out of the room if you are going to let your hamster out to roam, and if possible make sure humans are not going to walk around. Block all areas that the hamster could get under or into as fireplaces and the sides of radiator pipes etc are wonderful places to explore.
Cage - wise make sure it is properly shut each time you put your hamster back and make sure toys are not so small that the hamster could get stuck in them or have sharp sides, Make sure baby hamsters cannot drown in water bowls or fall from great heights.
Hamsters love to dig. You can make a digging tub by taking a deep waste bin and half filling it with shavings or dry peat. Ensure there is a foot between the top of the bin and the sawdust so the hamster can't escape while you are not looking. Remember if he digs down a long way, it may take a while for him to surface.
Hamsters have long front teeth, the incisors, which are for gnawing and nibbling. Hamsters also have teeth at the back of their mouths, which are grinding teeth to enable them to crush the hard seeds and nuts, which are their normal diet. The enamel on hamster's teeth similar to all rodents is yellow. If a hamster breaks one of it's teeth it may need the other clipping to the same length to ensure it can bite evenly. To do this, get some sharp clippers. Get as much of the scruff of the hamster as you can. Hold it upright and put the clippers firmly behind the tooth to be clipped and cut quickly! You do need a very good grip of the hamster as they have very loose skins and can almost turn round in them. Good luck. Remember hamsters have very long teeth anyway and as long as they are approximately the same length and straight they do not need clipping.