Antlers. They have fascinated man since the beginning. Going back thousands of years, one can see man’s love for animals with antlers etched and painted on the walls of caves. Antlers were a trophy in a different way before they were used to decorate walls of our hunting camps and game rooms. Before modern civilization, antlers were used to make tools, ceremonial wear, and weapons just to name a few. So how do these intriguing bones grow? What are they made out of? How do they go from this soft looking, furry velvet, to a durable set of rock hard fighting gear?
Antler genesis is an amazing process and is one of the fastest growing tissues known. The antler growing process for whitetails is an annual event and is regulated by hormones which are controlled by the photoperiod or length of day. The primary hormones responsible for antler growth are testosterone and IGF (insulin like growth factor). The rise and fall of testosterone levels initiates the peeling off of the velvet and the casting or shedding of the antlers, while IGF that is produced in the liver promotes actual growth. The longer days correspond with a drop in melatonin production; this kicks off the hormone cycle for antler growth. You can get very scientific and complicated with all the glands and organs involved in this process, but basically a buck’s brain measures the length of day by the amount of melatonin produced. This in turn influences testosterone and IGF levels. If you have ever noticed the bucks that are late in the velvet shedding process are often the yearling bucks and older bucks that have survived and are past their prime. This is directly related to the lower levels of testosterone output.
To fully understand antler, and more specifically, velvet antler growth we need to start at the beginning. In a whitetail’s case, the beginning would be the pedicel. The pedicel is the base from where the antlers will form and are located on the frontal bone of the skull. Buttons begin to grow from the pedicels somewhere around 6 months of age in male whitetails. During the growing season (spring& summer) a whitetails antlers are covered in a very fine and soft membrane most commonly called velvet. Underneath this furry membrane, the antlers are supplied by a very rich supply of blood and nutrients by veins that run on the outside of the antlers and back down to the base. During the growing stages, antlers are high in water and blood content and low in dry matter. The dry matter at this stage is around 80% protein and 20% phosphorous and calcium. Conversely, in the hardened stage, antlers are about 60% phosphorous and calcium and 40% protein. While in the velvet stages, antlers feel alive and warm to the touch because of all the activity taking place inside. I was lucky enough to feel this first hand while helping raise whitetails for a couple years.
When antlers are in velvet, they are very vulnerable to being injured. Bucks seem to be very aware that they have this fragile treasure on their head and are very careful in their actions through antler genesis. Bruises, cuts, or tears to the velvet can all have an impact on the formation of the antler. These injuries often result in abnormal points or in serious injuries complete deformation. It is worth noting that leg and pedicel injuries can also lead to deformed antlers. Vehicle collisions, bullet or arrow wounds, and fighting injuries to the legs, shoulders, or hind quarters can be seen sometimes in the following season’s antler growth by abnormal points or deformed main beams. Injuries on the rear legs affect the opposite side antler, where front leg or shoulder injuries will affect the same side. Research shows this oddity may be from the buck’s ability to pull or redirect nutrients for healing the injured leg. Pedicel injuries can happen during the numerous fights during the rut causing part of the pedicel to shed with the antler. If the pedicel injuries are bad enough, they can sometimes affect antler growth for several years.
With the days of late summer getting shorter, testosterone levels begin to rise and the growth cycle begins to slow down initiating the process of hardening or mineralizing of the antlers. So how does the velvet come off? The velvet ceases to be fed by blood by the formation of what some call the base or the burr on the antler. When the buck grows this burr at the end of the antler cycle, it puts a “kink in the hose” so to speak, cutting off the blood supply to the velvet. In as little as a few hours, the drying velvet is rubbed off on trees and bushes the buck is left with a blood stained rack that he will continue to polish for several days. I think many early fall rubs that are seen are areas where bucks use sapling trees and bushes to scrub the drying velvet from their newly hardened set of headgear.
There are rare cases where a buck does not shed his antlers, and instead keeps a velvet covered rack that continually grows throughout the year. The condition is referred to as cryptorchidism. These “cactus bucks” are the result from an injury or castration of the testes at some point which alters their testosterone levels. The age at which the injury occurs will determine the severity of antler deformation or interruption in the normal antler cycle. Fawns that are castrated will likely not develop a pedicel and therefore never grow any antlers. An older aged buck that has a testes injury or castration while he is hard antler will likely shed his antlers early due to the sharp decrease in testosterone production. The following season the buck can grow a rack that is permanent and stays velvet covered and growing.
The antler growing process is very interesting and one of the most unique cycles in the animal kingdom. Whether it be whitetail, mule deer, or elk, antlers are a large part of hunters fascination with these big game animals.