Ok, so I bought two supposedly female hamsters from pets at home last week, they were getting along fine until a few days ago when they started fighting. The smaller one seemed to chase the big one quite a lot and wouldn't let her in the house along with her. Today when I came home I noticed the larger one was bleedin from it's tail end, I am worried about her.

The hamsters are from the same litter and were living together in a smaller environment along with other hamsters in the pet shop. The sales person told me they would play fight but this is a bit more serious.

When my brother had hamsters he was told that they were both girls, but we found out otherwise when one kicked the other out and then had babies, could this be the case with my hamsters (although it is the smaller one who is aggressive) and what should I do?

You need to separate them. Hamsters are solitary animals by nature and do not do well living with other hamsters for a long period.

Some types of hamsters will fight to the death.

Please don't believe anything a pet store sales person tells you about the animals that are sold. Most of them are clueless. Hamsters, as J_9 indicated, don't "play fight." Please separate them.

Oh dear :( guess I'll have to do that. Thanks guys

This is why I hate pet stores. They hire teens that don't know anything about animals, and then it's all about selling those animals. They don't give a damn about the health and welfare of the animals they're selling.

If your hamsters are Syrian hamsters (most pet store hamsters are), then they should never be housed together. They're only kept together at the pet store because they're still young, but once purchased they should be separated and kept separated. They will fight to the death.

I know that we humans feel everyone should have a friend, and that hammy will be lonely without one. That's not the case. Syrian hamsters must be alone. They prefer it that way. They only come together to mate in the wild.

Time to buy another cage and get these two separated.

Everywhere I've looked it says they like to live in same sex pairs, they are russian dwarf hamsters

Everywhere I've looked it says they like to live in same sex pairs, they are russian dwarf hamsters
Well, in real life, your hamsters are not getting along, so that should tell you to separate them. Etiquette classes will not help.

Everywhere I've looked it says they like to live in same sex pairs, they are russian dwarf hamsters

Russian dwarfs can get along. They're one of the only breed of hamster that can, but same sex often doesn't, and opposite sex is asking for trouble.

All animals are different. Your two are telling you loud and clear that they don't want to be roommates.

Your problem is Pet stores tened to be well... EVIEL. I'm not blaming you at ALL I'm glad your concerned. You need to separate them most hamsters do not need to be with otter hamsters. Tess they could have sexed them wrong but most likely they have just gotten older and there hormones tell them to fight. After they are older they really don't "play fight" and most will fight to the death. Sorry about having to bye a nother cage but that prob the best saloshion that don't end with one if not two dead pets.