Antlers are bony extensions of a deer’s skull, unique to members of the Cervidae family. These temporary structures are composed primarily of bone and are regrown and shed on an annual basis. Found predominantly on male deer, antlers are among the fastest-growing bones in the animal kingdom. They play a significant role in the animal’s yearly cycle and social hierarchy.
Antlers Versus Horns
Antlers are fundamentally different from horns, despite the common confusion between the two terms. Antlers are composed entirely of bone tissue and are shed and regrown each year. Horns, conversely, are permanent structures found on animals such as cattle, sheep, and goats (Bovidae family).
A horn is a two-part structure consisting of an inner bony core, which is an extension of the skull, covered by an outer sheath of keratin. Horns grow continuously throughout the animal’s life and do not branch, with the exception of the pronghorn, which sheds its keratin sheath annually.
The Annual Cycle of Growth and Shedding
The growth of antlers is a rapid, hormone-regulated process that begins each spring, initiated by increasing daylight hours. New antlers emerge from bony supporting structures on the skull called pedicles. During this initial phase, the antlers are covered in “velvet,” a soft, highly vascularized skin. The velvet supplies the growing bone with oxygen and nutrients, allowing for rapid development that can reach up to one inch per day in some species.
As summer progresses, the antlers begin to mineralize, or harden, from the base toward the tips. Once hardening is complete, blood flow to the velvet is cut off, causing the tissue to dry and die.
The deer then rubs the dried velvet off against trees and shrubs, leaving the surface polished. After the breeding season, a drop in testosterone levels triggers specialized cells to de-mineralize the bone where the antler meets the pedicle. This weakening connection causes the entire structure to fall off, or be “cast,” typically between late December and early March.
Composition and Purpose
The final, mature antler is a dense, hardened structure composed of approximately 60% ash and 40% protein, rich in minerals like calcium and phosphorus. The primary function of the antlers is to serve as a weapon for male-male competition. During the breeding season, or rut, males use their hardened antlers to fight rivals and establish a dominance hierarchy.
Antlers also function as a visual display, with larger racks signaling the male’s health and genetic quality to potential mates. After the antlers are shed, they return nutrients to the ecosystem, as they are often consumed by rodents and other small animals for their high mineral content.