Not only deer, but all antlery animals (moose, reindeer, elk, etc). It’s completely normal and pain free, but it looks like something out of a horror movie.
For some reason, this does not happen to animals with horns, such as cows.
Unlike horns, which like finger nails grow from the base, antlers are basically bones.
It always weirds me out that antlers just fall off. Like, bone isn’t supposed to do that for us. What if we randomly shed bones every year?
If you’ve ever seen the skull of a horned animal versus an antlered animal the difference between antler and horn is pretty clear. The center of a horned animals horn is bone and forms a single continuous piece connected to the skull, surrounded by flesh and hard keratin (like finger nails). Antlers grow more like a knuckle, not connected to the skull as one continuous piece.
Another horned oddity is the rhino, whose “horn” is more like a specialized fingernail (keratin again) than a true horn. A rhino “horn” is like a compressed lock of hair filed to a point, a hair shiv if you will.
Yet another weird horn like thing is the giraffe. They have bone knobby lumps on their head that are like something between a horn and an antler, being bone fused to the skull surrounded by flesh but without keratin.
Then there are narwhals. I don’t know anything about narwhals. But they are cool and have “horns”.
