Cause and Effects of the 200 Days of Antler Growth

Whitetail Institute Staff Wildlife Biologist

What makes deer hunters get up morning after morning, check the weather, wind direction and head out into the cold to sit and freeze for hours? For most hunters, it is the desire to kill a big-antlered buck. Many hunters are driven for that one chance to get a deer of a lifetime, and many spend a lifetime awaiting that chance. What is the magical attraction of hunters to antlers? This is a question that involves much conjecture and is very difficult to answer. One thing we can tell you, however, is how antlers are made.  Knowing what makes antlers grow can better equip you to harvest that deer of a lifetime.

We all know that velvet covers and protects the antler while it grows. The velvet is very important due to its function of transporting the critical nutrients to the growing antler. The velvet consists of thousands of blood vessels, which makes the growing antler feel almost hot to touch. If the velvet is damaged it can cause deformities in the rack and will bleed very heavily for a short period time. Due to the high number of blood vessels in the velvet-covered antler, it does bleed for a short time when rubbed off in late summer or early fall.

Protected by the velvet is the growing antler. The growing antler inside the velvet is made up largely of a protein substance called collagen. In fact, the growing antler consists of about 80 percent protein. Because the antler consists of so much protein, it is vital that bucks consume high protein food during and before the antler-growing season. The antler-growing season is approximately between the months of March and August but can vary slightly across different areas of the country. So planting attractive, high protein food sources such as Imperial Clover can dramatically improve antler growth.

As the antler grows, the flow of blood supplies nutrients to the antler. While protein is an important nutrient, it is only one of the nutrients involved in antler growth. Another important nutrient group are minerals. Over the course of the antler growing process, minerals are deposited on the protein matrix of the antler. This process is called mineralization. During mineralization, massive amounts of minerals are needed to harden the antler and make it a solid bone.

Minerals are taken from the deer’s skeletal system and from the diet and deposited into the antler. The process of minerals being taken from the skeletal system and deposited in antlers is a form of osteoporosis. Due to the fact that antler growth is secondary to the overall health of the deer, the deer’s body will decrease the exchange before harm is done to the skeletal system. This is why mineral consumption is very important to antler growth. During the 200 days of the antler-growing period, intake of minerals will increase. Adding mineral supplementation to your management program will help to ensure adequate amounts of minerals are available to maximize antler growth.

So, what causes all this to happen? Hormones affect every biological function of a deer’s life. From the beginning of antler growth to the shedding of antlers, hormones play a role. White-tailed deer breed during the shortest days of the year, which are the winter months (short-day breeders) when the daylight decreases. The secretion of melatonin is stimulated by darkness. As spring approaches, the days get longer and the secretion of melatonin decreases and causes antler growth to begin. Added to this is a small spike of testosterone to start the growth of the antler. Growth hormones appears to have effect on antler growth, as yearly levels are highest just before the antler growth begins and decreases shortly after the majority of antler growth is done. 

During the construction of the antler, prolactin and growth hormone are at the highest levels. Then in the fall, the growth stops, the rut begins and melatonin levels increase.  Testosterone, along with other hormones such as calcitonin, causes the growth to stop and mineralization to speed up until a hardened antler is produced. There are other hormones that play a role in antler growth, but I only will mention the key hormones. Antlers drop in most areas in late January into February but in some states it can be later due to the increased testosterone in areas that have a later rut. I have personally seen deer in April with antlers.

Antler growth is a very complex and fascinating process. It is hard to believe that the process that only takes 200 days. So the next time you’re at the beach on vacation during the summer, you can understand what is going on in the woods and impress your friends by saying, “Did you know that the prolactin hormones in bucks are at is highest level as we speak.” That should make for a good conversation.