A wild animal documentary that I saw mentioned that stags would eat their own bloodied velvet hangings that were scratched off on branches ("velvet" is the livi

A wild animal documentary that I saw mentioned that stags would eat their own bloodied velvet hangings that were scratched off on branches ("velvet" is the living covering of the antlers at the beginning of the growing season). It claimed "biologists don't know why the deer, which are herbivores, eat the bloody remains." Which is stupid, of course. The answer is because deer can't read, so they don't know they are "herbivores".