This morning I saw one of my hens lying on the ground. Upon inspection it appears that something has eaten the flesh off the "drumstick" of that leg. The bones are not broken but are exposed. She drags that leg when hopping. Is there anything I can do for her or is it time to put her down? What might have done this? I found no other injury on her or any other bird. I did see where a small animal dug under the door but it was only about rat sized.