When antlers start to harden, bucks will shed their velvet by rubbing it off on trees, shrubs, and even fence posts. deer use velvet to grow their antlers. The antlers underneath the velvet start out as cartilage; therefore, they need oxygen supplied from the velvet to grow.
The antlers underneath use the flow of the blood-rich oxygen in the velvet to strengthen and calcify into bone. Velvet antlers are equipped with tiny hairs that improve the deer’s sensory function and heat regulation throughout the antlers. The improved sensory function helps gives them more feeling in the antlers so they can easily navigate through thick buck bedding areas without getting stuck or damaging their antlers. The blood supply to the velvet is cut off which makes the velvet antlers dry and harden. This hardened velvet creates an uncomfortable itch since it has a tighter grip on the antlers underneath.
When they feel this itch, deer start rubbing trees and other rough surfaces to remove the velvet.
The friction between these surfaces helps remove the bloody velvet and leaves the polished and hardened antlers underneath.