Deer are ingrained in North American culture. Their range is global. They are one of the most studied families in the animal kingdom. The fascination in deer lies not only in their economic and ecological importance but in their agility, beauty, and grace. Not least among their striking characteristics are their antlers, which can be quite magnificent in some individuals. Antlers are unique to deer which are the only animals that have them.
Males of all deer species, except the Chinese water deer, possess a set of two antlers of usually symmetrical proportions on either side of their foreheads. Antler growth is even more remarkable than their mere presence. Unlike horns, antlers are true bones that serve as branched extensions of the skull. Deer typically shed them annually. Interesting side notes are elk do not shed their antlers, and female reindeer or caribou normally have antlers. Very rarely do normal females of other deer species grow antlers.
How do deer antlers grow?
Antlers start like most bone as cartilage. Bone for each antler grows from a cartilage base, also known as the pedicle. Velvet, the downy skin that covers antlers in their early stages, provides nutrition and blood supply for growth. Antlers are one of the fastest growing tissues in nature, growing up to an inch (2.5 centimeters) a day in elk. The quarter to half an inch per day by smaller species is still remarkable.
Velvet covers a deer's antlers until they reach full growth, which occurs after three to four months. Once this happens, blood supply is disrupted and the velvet peels away. At the same time, the antlers become hard and much less fragile.
Deer require a high protein diet to cope with antler growth that correlates with a stressful breeding season. A protein diet of 16 percent or more led to significant increase in length and breadth of antlers over those fed six percent protein or lower. Calcium and phosphorus, along with possible other minerals (potassium, manganese, and iron), are vital for healthy antlers and their growing needs.
When mating season ends, a deer usually sheds his rack. This will occur from late autumn to early winter. Mid to late spring signifies a start to the new cycle.
What determines antler size?
Relatively few factors affect antler size in adult deer.
Nutrition is the single most influential contributor to antler growth. Bone origin and expansion rate of antlers suggests significant energy output and a large requirement for vitamins and minerals. Simple observation illustrates that herd members with poorer nutrition have smaller (sometimes even deformed) antlers as opposed to their well-fed counterparts.
Hereditary traits are believed to have vital roles in antler size and rate of growth. Although a genetic influence is difficult to determine in a species so heavily hunted, regional variations in antler size and studies of captive herds support the theory of its significance.
It may not be possible to determine exact age by antler size, but maturity plays a factor. Young bucks under a year are still growing at a rapid rate and do not have extra resources to invest into antler growth. As buck growth tapers, antlers develop the capacity to become larger. Whitetail and mule deer are fully mature between four and six years old and at this time are able to reach their full antler potential.
Finally, a buck's health will determine how large his antlers will potentially grow. This is not always directly related to nutrition. Many deer with severe injuries to a leg, for example, will grow a small or defective antler on the affected side. Deer often have gnarled or stunted antlers for unknown reasons, perhaps related to past trauma or underlying illnesses.
How big can deer antlers grow?
In several game species, young bucks grow their first set of antlers when they reach ten months of age or become yearlings. This set is often represented by basic spikes but can be as much as ten points or five tines on each side.
Even at two and a half years old, ongoing data suggests a buck's antlers have likely only grown 25 to 35 percent of their full potential. A "typical" deer of this age has seven points and an outside breadth of about sixteen inches.
Maximum antler size is often not achieved until deer are five to eight years of age. Moose and elk may reach ten years of age before they peak. Depending on the type of deer, their antlers can be over twenty points and near twenty inches of inside spread. Moose antlers are closer to fifty inches of outside spread. The impressive fact is to imagine this amount of growth over a mere four months.
Once a deer passes his prime reproductive age, peak antler growth potential and size begins to slowly decline. This is related both to decreasing testosterone levels and lower ability to absorb nutrition (changes in metabolism, aging teeth, etc).
Deer antlers grow like any other bones in his body, but at an accelerated speed. They have been modified by natural evolution for mate rivalry and selection. Human activity in the form of trophy hunting has also contributed to larger racks. Ultimately, the most awe-inspiring antlers represent the crowning glory of a buck deer in his prime when he is at his healthiest and best able to help propagate his species.