For the Smoky Mountain herd, March is the beginning, and also the end of the yearly antler cycle. Testosterone is the chemical in elk that controls the development of antlers each year. During the spring an elk’s testosterone levels drop, which causes the bond between the antler and the pedicle to weaken, and the antlers fall off.
Usually both antlers drop within a 24-hour period. As the days begin to lengthen, testosterone levels in the bulls’ blood increases, signaling the onset of new antler growth.
Antlers begin growing as soon as the previous year’s set has fallen off. Antlers can grow as much as an inch a day during the spring and summer months and are considered one of the fastest growing tissues in the world.
During this development, they are covered in a soft layer of velvet that functions very much like skin. The antlers are living tissue, and the velvet layer contains veins and capillaries that carry blood and minerals to the developing bones. While still in velvet, an elk’s antlers are light and somewhat malleable. They continue this rapid growth for about four months until they reach full size.
Sometime around August, a bull’s antlers will fully mineralize and the new hardened bone will emerge. As the antler hardens, blood flow to them is halted and as a result, the velvet begins to fall off. This velvet will be shed over a 24-hour period, usually rubbed off against trees, and the newly emerging antlers will appear bloody for a few days afterward. These new bones, which can weigh up to 40 pounds, are made up of calcium, phosphorous, and up to 50 percent water.
As a bull ages, his antlers will continue to grow larger each year provided that he is in good health and there is an abundance of nutrient-rich food. Larger racks are typically a sign of mature bulls in good health, and signal to the cows that they are a worthy mate.
While the antlers are developing, a bull does little besides eat to ensure that he has enough nutrients to grow a large, uniform rack capable of defending himself and competing for the right to breed when the rut begins. Bull elk will carry these antlers and spar throughout much of the fall and winter until March rolls around and the process begins all over again.
Joe Yarkovich is a biologist with the Great Smoky Mountains National Park elk management team.