Hi. A smal percentage of gliders for whatever reason try to "pull" the pain or discomfort out with their teeth while making a horrible noise, I have heard of a few that did not make the noise, they quietly mutilated or crabbed every now and again. I wish I could tell you the cause and if it could be one of yours but I cant. I will never for get the night in Jan. 2008 when I went to do my last glider checks and Spencer was ripping at his cloaca and making that horrible sound, splattering blood every where. Not good. He is fine now though, however he will aways be dubbed as a mutilator so I had his bottom incisors removed to break the cycle. Some confuse mutilation with overgrooming. Missing fur on head or tail is overgrooming. The head is usually stress or from the heart, The tail is normally a physical illness. Hope this helps