As you may have realized I have two sets of boys. I now have the big boys on the bottom and the little boys on top. They don't seem to get along one vet trip and weeks of introduction later we're still having issues. The newest one involved Brisby and the big boys. Brisby will sit by the *hole* in the middle floor of the FN (for those who don't have FNs there is an opening in the middle floor which you can close up with the ramp or leave open) and every time he sees a big boy he makes a loud horrible squeal. The first time I heard it I thought one of the big boys had grabbed his tail through the bars or was biting him. But there is no actual contact between the boys. Does anyone know why they are doing this?