Science of Whitetail Antlers: Big Questions Answered
What exactly are deer antlers? How do they grow and develop? What's their purpose? What influences antler size?
As long as humans have hunted deer, we’ve been fascinated by antlers. Our ancestors have used them as tools, weapons, medicines, decorations and ceremonial symbols in tribal rituals. We’ve even used them as alleged aphrodisiacs. Today, hunters spend millions of dollars and countless hours in search of the biggest antlers.
But even with our long history of antler worship, many antler questions remain. What exactly are antlers? How do they grow and develop? What’s their purpose? What influences antler size?
Antlers are special – and not just because they’re a source of bragging rights among deer hunters. Antlers are one of the fastest-growing tissues known to man, rivaled only by some forms of cancer. Because of their unique properties, scientists study antlers in hopes of finding potential treatments and perhaps one day a cure for cancer.
The rapid growth of antlers – about 1/8 inch per day – also makes them a source of interest for researchers looking into treatments and cures for other maladies such as osteoarthritis. They’re also a tissue of interest for research into organ and limb regeneration.
Antlers are exclusive to the deer family, Cervidae, which includes elk, moose, whitetails and mule deer. Unlike horns, which are permanent and won’t grow back if lost to injury, antlers are shed and regrown every year.
Hardened antlers are made up of roughly 45 percent protein, 22 percent calcium, 11 percent phosphorous and 1 percent fat. They also contain magnesium, sodium, aluminum, potassium, copper, manganese and zinc. The chemical composition of antlers varies with location and can be affected by environmental factors such as soil characteristics and the amount of rainfall during the antler growth cycle.
The antler growth cycle is greatly affected by photoperiod, which is the amount of light present in a day. When days grow long in the summer, bucks produce higher levels of testosterone, which in turn triggers antler development. Antlers start as cartilage growing from bases called pedicles. A fuzzy skin known as velvet, which is rich in blood vessels and sensitive to the touch, supplies the growing antlers with essential nutrients.
As the amount of daylight dwindles later in the summer, bucks go through another testosterone increase that triggers a mineralization and hardening of the antlers. Bucks rub their antlers on vegetation to remove the velvet and reveal bony antlers, which are carried throughout the fall and winter. At the end of the breeding season, a drop in a buck’s testosterone level triggers the antlers to release from their pedicles. Within days of the formation of a scab-like material over the pedicles, the process starts anew with the development of new antler-growth cells.
The significance of photoperiod to antler development can’t be overstated. Much research has been conducted on the effects of light on antler development. In controlled laboratory experiments, bucks have been capable of producing multiple sets of antlers in a single year, as well as retaining a single set of antlers for several years, just by altering the amount of light to which the bucks were exposed.
Antlers likely serve multiple purposes, but biological research still hasn’t found a definitive answer to why male deer have antlers. It’s likely that antlers help with defense against predators, but because they’re present only in male deer, it’s doubtful that predator defense is the primary reason for antler evolution.
Another explanation may be that antlers serve as a signal to display dominance to other bucks. The theory goes that a large rack will deter potential competitors from engaging in actual combat, thereby reducing potential for injury, energy expense and death.
While whitetails use threat posturing and sparring to establish dominance during the breeding season, the size of the antlers alone probably isn’t enough to establish that dominance. Rather, it’s a matter of what a buck can do with his antlers. Just before and during the breeding season, whitetails commonly spar by locking antlers and pushing and shoving each other to determine the stronger of the two bucks, with the “loser” assuming a subordinate role in the company of the stronger buck.
Yet another explanation may be that antlers serve as a signal of genetic quality to female deer, reflecting age, health and nutritional status of a buck. Although the jury’s still out on the ultimate reason for the evolution of antlers, many biologists agree that they likely serve as both “armaments and ornaments.” They probably evolved as armaments to facilitate combat among bucks, and they probably also play a secondary ornamental role in attracting mates.
The three-legged stool of antler quality consists of age, nutrition and genetics. From a hunting perspective, age is probably the most important because it’s the easiest to manipulate and progress is easily documented. Studies have shown that whitetail bucks, on average, produce 28 percent of their ultimate maximum Boone and Crockett gross score at one year; the percentage increases to 62 percent at two years; 78 percent at three; 92 percent at four; and 99 percent at five.
So by allowing a buck to move from one to two years, a hunter or herd manager typically doubles the antler size in that buck. Nutrition also plays a critical role, and it’s also another facet that is somewhat within the hunter or land manager’s control. By increasing habitat and forage quality and quantity through forest management and supplemental plantings, the land’s nutritional value may be increased, therefore leading to increased antler development.
Research has shown that protein is key to antler development, with an optimal level of 16 percent protein in a whitetail’s diet from spring through autumn. Genetics is obviously important to antler size because a whitetail’s headgear will only grow as large as its DNA will allow. But genetics is also largely outside the hunter or land manager’s control and therefore hard to manipulate. Most biologists agree: When trying to grow bigger-antlered deer, focus on age and nutrition and forget genetics.
Of course, there are other factors that influence size and shape of antlers. Birth dates have been shown to have an effect, with later-born fawns exhibiting less first-year antler growth than their year-class cohorts born earlier in the year.
An Alabama study, for instance, showed that forked-antler yearlings had an average birth date of roughly a month earlier than spike-antlered yearlings, and a similar comparison in Mississippi found that fawns born in August/September were more often spikes and had fewer antler points at one year than fawns born in June. These effects are more common in southern latitudes because there’s less variation in breeding dates in northern latitudes.
Variation in antlers also shows up as a result of regional soil types and land-use patterns that affect habitat and nutrition. Injuries and genetic predisposition also can affect antler size and shape, and the prevalence of abnormal points such as kickers and drop tines and other abnormalities such as palmation and clustered tines increases with a deer’s age.
It’s important to keep in mind that incredible variability exists in whitetails and their antlers. Just as every hunter is different, so is every deer. Myriad factors go into the development of antlers, many of which are beyond a hunter’s control. Perhaps that’s why our fascination with antlers never seems to fade.