It may be that the blood you saw came from your hamster’s urinary system or from the rectum. Blood in the urine can indicate a few things, such as bladder stones and a problem with the kidneys. However, kidney problems, such as chronic renal failure, are usually seen in older hamsters, and the signs include excess drinking and urination plus blood in the urine. If none of these symptoms had been apparent this is unlikely to be the cause of death in a young hamster.

Diarrhoea, such as Tyzzer’s disease, can result in hamsters dying quite suddenly. Salmonella infections can also be fatal. There can be severe soiling around the anal area. Although wet tail and a rectal prolapse that can follow on from this are infrequent in Russian hamsters, they can still happen so this may have been a factor.