Antlers are among the most identifiable characteristics of species of the deer family, Cervidae, which comprises caribou, elk, moose, mule deer and white-tailed deer. Antlers have been prized and pursued by hunters for many centuries. Their rapid growth and deciduous (regrown each year) nature has made them fascinating for hunters and wildlife enthusiasts alike.
Antlers are often referred to as “horns”, but they are not. Horns are found on sheep, goats, and cows and are formed from hair-like tissue that grows over a bony core. Horns are typically not shed, and some species, like big horn sheep, can be aged by counting the annual growth rings on their horns. Unlike horns, antlers are true bone and are composed primarily of calcium and phosphorus.
So what purpose do antlers serve? Four of the most popular theories are described below.
Signal of male quality
Because they are grown mainly by male deer, antlers are thought to serve as a visual cue signaling health and genetic quality to female deer. If this were true, females could determine the quality of potential mates by evaluating their antlers.
Weapon used to fight other males
During the breeding season, male deer use their antlers to fight and establish dominance over other male deer. Male deer will often lock antlers and push one another to determine which individual is stronger, therefore establishing a dominance hierarchy between individual animals.
The size of antlers on deer has been thought to display age-related dominance between males without the males actually having to fight. If this were so, a dominance hierarchy could be established within the male segment of the herd without the risk of serious injury or death.
Defense against predators
Some researchers have suggested that deer may use antlers to defend themselves against predators, as antlers can inflict severe injury. Although this theory may be true, it would mean that females are always defenseless and that males are defenseless once their antlers have shed and during the antler growing phase.
The Growth Cycle of Antlers
The annual antler cycle is ultimately controlled by day length or photoperiod. The brain contains a kind of clock that measures the periods of light and dark and uses this information to ultimately control the secretion of the reproductive hormone testosterone in males. Testosterone controls the antler cycle. In tests, bucks kept in constant 12 hours of light and dark were unable to shed their antlers and grow new ones, and bucks kept in constant light grew and lost three sets of antlers in two years.
Growth of antlers typically begins in April in response to increasing day length. In fact, antler growth is one of the fastest known types of tissue growth in mammals, and a deer’s antlers can grow at a rate of ¼ inch per day.
When the antlers are growing, they are full of nerves and blood vessels and are covered with a hairy skin covering tissue commonly called “velvet.” Antler growth is like building a skyscraper. What is first built is the structure or a frame or matrix. Think of pouring concrete; you must first build a form. That is what deer do. During the early summer, deer antlers are soft to the touch or spongy. Towards the middle of summer, as the form is being finished, the deer begins to “pour” the bone.
By late summer, as day length decreases, testosterone levels begin to increase, the form is filled, and the antler begins to harden. Finally the blood vessels within the antler itself are filled and lose their ability to nourish the velvet, and it dries up and falls off. The velvet is typically totally removed in a day, and some of it may be eaten by the buck.
Antler size is determined by three factors: age, nutrition, and genetics. Age is pretty simple, as a buck gets older his antlers get bigger. Nutrition is also simple as a deer has to have enough to eat to grow antlers. As deer population density increases, overall herd condition and reproductive rates decline. Genetics, on the other hand, is not simple, but just like in humans genetics play a role in the overall health and antler size in deer.
Lastly, one interesting fact about deer antlers is the impact that injury to the back leg of a buck has to antler development on the opposite side. The next time you see a deer with a normal rack on the right side and a stunted rack on the left, check its right back leg for an injury!
Biologist, T. M. (2017, November 30). The importance of antlers. Retrieved from https://www.wxpr.org/post/importance-antlers#stream/0
Pierce, R. A., Sumners, J., & Flinn, E. (2012, January). Antler Development in White-tailed Deer: Implications for Management. Retrieved from https://extension2.missouri.edu/g9486.