Antlers are complex bone structures that grow from an animal’s skull and are completely shed and regrown every year. This yearly cycle involves dramatic physiological changes, meaning the coloration changes significantly depending on the stage of growth and the environment. The color transforms from a soft, blood-rich covering to a hardened, stained bone, resulting in a wide range of shades.
The Appearance of Antlers in Velvet
Antler growth begins as an extension of the skull, covered in a soft, fuzzy layer of skin referred to as velvet. This living tissue is highly vascular, supplying the massive amounts of protein and minerals required for the fastest growing bone in the animal kingdom. During the peak summer growth period, the rapidly developing bone can increase by as much as an inch and a half per week in mature animals. Antlers in velvet typically appear swollen, grayish, or even reddish-brown due to the constant presence of circulating blood and the fine hairs of the skin. This living layer is sensitive, and the animal takes great care not to damage the structure while it is still growing. Once the antler reaches its full size, the blood supply to the velvet is cut off, signaling the end of the growth stage.
The Hardened Structure and Base Color
Following the completion of growth, the velvet dies and begins to dry out, triggering the animal to rub it off against trees and brush. This action reveals the fully calcified, hardened bone structure underneath. The mature antler is composed primarily of calcium and phosphorus, similar to dense skeletal bone, with a compact outer layer and a spongy interior. The inherent color of this fully formed bone, before any external exposure, is a pale, off-white or grayish-white. This shade is rarely seen in nature for long, as the process of removing the velvet immediately begins to change the surface appearance. The surface texture of the bone, including the channels etched by arteries in the velvet, also influences how subsequent colors are absorbed.
Environmental Factors Shaping Final Color
The dark brown color commonly associated with mature antlers is not the natural color of the bone but is entirely the result of environmental staining. This coloration begins with the removal of the velvet; if the animal rubs the velvet off before the blood has completely dried, the oxidized blood residue can immediately stain the bone a dark hue. The primary factor dictating the final shade is the process of rubbing the hardened antlers against woody vegetation. As the animal scrapes the antlers on trees and shrubs, the bone absorbs pigments from the bark, sap, and plant tannins. Different tree species yield different colors: pine or cedar bark often imparts a reddish or darker brown color due to resins and saps, while certain hardwoods may result in lighter tan or gray shades. The mineral content of the soil, which influences vegetation composition, also contributes to the final palette, leading to variations that range from light tan to a deep chocolate brown.
Antlers Versus Horns
The color variability and annual cycle of antlers stand in sharp contrast to the headgear of other animals, such as horns. Antlers involve a complete annual color change from velvet to hardened bone. This cyclical nature means the color is constantly changing based on the season and the animal’s recent activities. Horns, on the other hand, are permanent fixtures found on animals like cattle, sheep, and goats. They consist of a bony core covered by a sheath of keratin, the same protein found in human fingernails. Because the horn structure is not shed annually and is covered by a sheath that grows continuously from the base, the color tends to remain consistent throughout the animal’s life. The only exception is the pronghorn, which sheds its keratin sheath yearly, but this is a unique trait distinct from the complete bone shedding seen in the deer family.