Looks like an accident waiting in the wings.
There used to be a bush or small growing tree in the pasture next to my building where the lady's llamas would move over it and scratch their bellies with it. Or at least one of them --they all look alike to me.
I'd spot that activity once in a while, but one day I realized the bush was gone. It's not like I was carrying out a surveillance assignment on it, just one day I noticed it missing. I could infer, without actually knowing, that one of them may have injured itself on it.
And of course, deer use trees to rub the velvet off their antlers, too.
Me, I use a good wooden backscratcher.
Terry