Wet Tail is a disease very common in hamsters that they get either from too much stress, or from another hamster (highly contagious). Basically they get diarreah until they dehydrate themselves to death. I highly recommend when bringina new hamster home to purchase some Dry Tail which is a liquid medication that you can either add to their water or force feed. My old hammie Zoe LOVED the stuff and would always be waiting at the door to get her "treat". I gave it to her every day for her whole life and she never contracted the disease and lived to be 4years old!