Why Is My Hamster Biting My Other Hamster On His Back?

The same thing was going on with my teachers 2 hamsters so if one is female she could be in heat like what Jim1949 said or shes pregenate

They can be in the heat or if your trying to make them have babys the male hamster will go on top of the female hamster and bite her on her back that's what happened to my hamsters

hope I helped Byyy :D:D

If you suddenly realize your hamster is getting fatter than you should separate the two and get ready for the new arrivals. If they are both females/males than you should put a mesh separate in the middle of your cage. Remember to put food in both sides! Wait a couple days then take the mesh out and see what happens. If they keep fighting do the process over again.

Could be - emphasis on could - that one is a male, one is a female, female in heat. Would separate them if possible.

If the hamster that's biting is a boy he might be trying to show hes the leader ...

Ps:
Some hamsters sometimes prefer to be by themselves aka solitary