As soon as a bull elk’s antlers finish growing, the mail hormone testosterone is introduced into the bull’s body and cuts off the blood flow to the antlers, essentially killing them. They quickly harden, and the bull then rubs the velvet protective covering off the antlers.
Even after the velvet has been rubbed off, the bull continues to rub small trees and saplings as he begins his rutting ritual. It is not unusual to find dozens or trees with the bark completely rubbed off them, and many saplings up to four inches in diameter may be broken off.
In the whitetail deer world rubs carry great significance for the hunter because they generally mark out the deer’s boundaries. An elk rub has not such significance. Instead, the rubs simply indicate the presence of a rutting bull in the general area.
This is not to say that rubs should be discounted when scouting for elk. On the contrary, several fresh rubs along a ridge are a sure indicator that a bull elk is living somewhere in the general area. He may have moved to the opposite hillside by the time you arrive to hunt. But rest assured, he should be within hearing range of your calling.