My hamster has that too today. I looked it up and its because it is constipated. There is really nothing you can do about it. But give it a small amount of lettuce because that makes their poop more wet. Massage its tummy lightly or its sides to help the waste move down. In some cases it may end up passing away. But if you sit there and help it it wont. Ive done what I just told you and he is starting to poop. Constipation is also caused by too much fluff bedding, lack of exercise, poor food or a lack of good water. So make sure your giving your hamster the necessary things. I believe mine was cause by the bed fluff.
