I have four Boer does, three and four years old. I never saw them do this before - they are rubbing their horns on trees, bushes and their shelter. The rubbing has stripped the bark from bushes and they do it in the evening when they are in their shelter. This started last week, and they seem to be doing it a lot. One seems to be doing it more often than the others. Like I said, this is the first I have ever seen them do this. Anyone know whats going on?