Okay, so recently I got two guinea pigs who I believe are getting along with each other? I have a cage and a playpen for them that is big enough for the both of them, of course, its empty so I need to give them toys and blankets for them to hide in, right? I also need to make sure, when I see them together they typically nip each other in the body but it only happens like sometimes only once an hour and then sometimes not at all for 2 more hours. Is this aggression or is this normal for Sows (or is it females?) to do when they are introduced?