Hi i was wondering what the best way to introduce two chins is. They are both 4 month old females and they are sisters. I brought home sophie first as we weren't sure if we could handle two but ended going back to the breeder 2 weeks later to get her sister sadie. They both lived in the same cage before i brought them home but when i let them both out for playtime they chased each other and sophie kept trying to mount the other chin. Sophie also kept "biting" sadie but i understand this is their way of grooming. Its kind of difficult to watch beacause to me it looks like shes trying to eat her face lol. The entire time they were playing both chinchillas were making contact sounds so i assumed everything was going good. Now my concern is that later on i noticed sadie had a small patch of fur missing from her left hip area but i didnt hear any alarming noises or squeals. Is this normal or should i be concerned. What can i do? sorry for the lengthy post.