I don't know what to do. We got a new Guinea pig yesterday but my old one appears to really dislike him. They fight each other and I have to pull them apart. My old one is being especially bold, chutting even when we move the other one to a different room and he can't even see him. I wouldn't have the heart to bring the new guy back but I can't make my old guy feel like he isn't loved anymore or that he is pushed out. What do I do?