It's probably poop that won't come out.
usually a boy hamster will get something that looks like a very large butt which is their testicles. Female hamsters will not get this. Usually boy hamsters from the store do not have this at first because their so young but after time progresses they will start to get this
it might be a long poop that happens sometimes
A butt looks like something round. With a crack straight in the middle
poop
Out of his butt.
none
Yes. Out their butt.
She's menstruating.
yes not sure what it is called but it means your hamster it going to die
a waffle that looks like a butt
No
if you have just cleaned it out it may have banged its nose or if you have to hamsters they may be trying to kill each other