Male deer, including white-tailed deer, moose, elk, and caribou, lose their antlers every year. Antlers are bone structures that grow from bony pedestals on the skull called pedicles. The annual shedding and regrowth of these structures represent one of the fastest rates of bone growth in the animal kingdom. This yearly cycle is timed to the seasons, ensuring deer have hardened antlers available for the breeding season.
Antlers Versus Horns
Antlers and horns are often confused, but they are different biological structures. Antlers are composed entirely of bone and are shed and regrown annually by members of the deer family, known as cervids. They are typically branched and grow as a single extension of the skull.
In contrast, horns are permanent structures that are never shed, growing continuously throughout an animal’s life. Horns are found on animals like bison, sheep, goats, and cattle (Bovidae). They consist of a bony core covered by a sheath made of keratin, the same material found in human fingernails and hair.
The Biological Mechanism of Shedding
Antler shedding is regulated by the fluctuation of the male sex hormone, testosterone. After the rut, or mating season, a buck’s testosterone levels drop significantly. This decrease initiates the formation of a precise separation point, known as the abscission line, at the junction between the antler and the pedicle. Specialized bone cells called osteoclasts rapidly reabsorb the bone tissue at this line. This degeneration weakens the attachment until the weight of the antler, or a slight bump, causes it to detach completely.
The Seasonal Timeline of Antler Growth and Loss
The annual cycle of antler growth and loss ensures antlers are available for the fall breeding season. Shedding occurs in late winter or early spring, typically between late December and early March, as testosterone levels are lowest. Once an antler is cast, a scab forms over the pedicle, and new growth begins immediately.
The period of rapid regrowth throughout spring and summer is known as the velvet stage. During this time, the soft, growing bone is covered by highly vascularized skin called velvet, which supplies the nutrients and oxygen needed for growth, sometimes up to one and a half inches per week.
By late August, growth is complete, and blood flow to the velvet ceases. The bone mineralizes, turning the antler into a hardened, dead bone mass. The dry velvet peels and shreds away, a process deer hasten by rubbing their antlers against trees and brush. This rubbing cleans the antlers, exposing the hard, polished bone surface just in time for the rut. The hard antlers are used for sparring with rival males and establishing dominance until the cycle concludes.
What Happens to Shed Antlers
Shed antlers, which are rich in calcium and phosphorus, rarely remain on the forest floor for long. They are quickly utilized by small mammals and scavengers. Rodents, such as mice, voles, squirrels, and porcupines, are the primary consumers of the discarded bone material.
These animals chew on the dense bone to wear down their continuously growing incisor teeth and to seek valuable minerals. Calcium and phosphorus are often scarce in winter diets, making the fallen antlers a temporary source of these essential nutrients. This process efficiently recycles the minerals from the deer back into the local ecosystem, where they are eventually absorbed by plants.