So I need some advice. I have had a guinea pig (Nibbler)for over a year now. We were informed that Nibbler was a female when we bought her but after buying a young female recently (Snarf) we were told by the vet that Nibbler is in fact a boy. So they have been living together for around a month now and more recently we have noticed that Nibbler is chasing Snarf around the cage growling and appears to be nipping her on the butt. Snarf runs from him squeaking, not like a loud "I'm in pain" squeak. Is this normal? I'm afraid that Nibbler is just bullying Snarf around and I don't want her to get hurt.