My grey chinchilla, Kulu, can be really bad about that. It seems to come and go in cycles. Lately he's been doing better but he's had a cage mate. I guess in a way that helped since I haven't had problems with him since before then. The cage mate, Spot, is another story. I have separated them as of Friday because they were pulling each other's fur out and it was escalating to where I thought it was getting dangerous. He was really bad about humping on Spot and I wonder if that was a contributing factor.
All chinchillas are going to be different. Kulu is prone to getting randy. Spot, my other chinchilla, is completely different and I've never seen him go after me. When Kulu gets randy he'll start by pulling at my skin. When that happens I just pull back and if that's not enough I'll pick him up and hold him against my chest so he can't go any farther. That's usually enough to stop him.
I know some chinchillas will pick up on other female animals or even people during their cycle. Some are just like that all of the time and you just have to deal with it. If you want to get him something be careful because your chances of observing fur rings becomes higher. For those that have done this the results seem to be mixed. It really depends on the personality of your pet.
