Deer antlers are some of the most iconic features of these common mammals. But not all deer grow antlers. If you’ve ever seen a deer without antlers, you may have wondered why.
If you’re short on time, here’s a quick answer to your question: Some deer, including most female deer and young males, naturally lack antlers. The antlers are used for competing for mates and establishing dominance.
In this comprehensive guide, we’ll explore the reasons why some deer have no antlers. We’ll look at the different types of deer, the antler growth cycle, and how hormones and genetics control antler growth.
Types of Deer Without Antlers
Females
Female deer, known as does, are one of the three groups of deer that typically do not grow antlers. This is due to their lack of testosterone production, which plays a key role in antler growth. Does still have antler pedicles, which are bony protrusions on their skull where antlers would normally grow.
These pedicles are covered in velvet skin. If given testosterone injections, a doe could potentially grow antlers!
On average, only about 10% of female deer have antlers. This anomaly occurs due to a hormonal imbalance that causes increased testosterone production. When a female deer grows antlers, they are often small and poorly formed.
Female deer use their antlers to establish dominance in the hierarchy and compete for resources.
Young Males
Young male deer, called bucks or fawns, do not grow antlers until they are about one year old. Up until this point, young males have velvet-covered pedicles similar to females. Around their first birthday, bucks begin developing button antlers, which are small rounded nubs.
Each subsequent year, the antlers will become larger and more branched as the buck matures.
Antler growth begins in spring when a buck’s testosterone levels peak. The speed of growth is extremely rapid, up to 2 centimeters per day. The antlers are covered in soft velvet while growing, which delivers blood and nutrients.
By late summer, the antlers stop growing and the velvet dries up and falls off. The deer will rub their antlers on trees to help remove the velvet. Male deer use their antlers for sparring, establishing dominance and competing for females during the autumn rut.
Castrated Males
Male deer that have been castrated, either in domestication or by injury, shed their antlers and fail to regrow them. This is because antler growth is heavily dependent on normal testosterone levels. Just like females, castrated males may still have pedicles covered in velvet skin where their antlers would have been.
Castration causes testosterone levels to drop significantly, disrupting the hormonal cycle that leads to antler regeneration. However, the pedicles do not disappear and can still be stimulated to grow malformed antlers if the deer is given testosterone supplements.
For deer farmers, castration is sometimes used to make males less aggressive and easier to handle.
The Antler Growth Cycle
Antler Growth
The growth of antlers in deer is an amazing process governed by hormones, nutrition, and age. Male deer, called bucks, grow and shed antlers each year. The cycle begins in spring when rising testosterone levels trigger antler growth from the pedicles, which are permanent boney protrusions on the buck’s skull.
Over the summer, cartilage develops into bone tissue which creates branching antlers covered in velvet, a soft furry epidermal layer containing blood vessels that supply oxygen and nutrients.
At peak growth in late summer, an adult buck’s antlers can grow up to 2 inches per day, which is one of the fastest growth rates of any mammal! By fall, the velvet dries up and bucks rub their antlers on trees to remove it, revealing the hard bone beneath.
Increased testosterone and the approach of mating season cause the antlers to mineralize completely and stop growing.
Antler Shedding and Regrowth
In winter, after the mating season ends, testosterone levels drop which causes the antler bone at the pedicles to weaken and eventually break off. Bucks shed their antlers from January to March each year. The pedicles stop supplying blood to the antlers so they die and fall off.
Almost immediately, new velvet covered antlers will regenerate each spring to restart the cycle again.
If a buck does not get proper nutrition, it may experience abnormal antler growth cycles. According to research from the Quality Deer Management Association (QDMA), about 10-20% of yearling bucks and 2% of adult bucks have antler deformities. Poor habitat and injuries can also affect antler growth.
The antler cycle is an outstanding example of how deer adapt to seasonal changes. Bucks grow majestic antlers to establish dominance and attract mates each fall. Then they shed their antlers in winter once their purpose is served to conserve energy. Truly an amazing process!
Factors Controlling Antler Growth
Testosterone
Testosterone is the key hormone that drives antler growth in deer. It is produced by the testes and other organs in response to changes in day length. As daylight increases in spring, testosterone levels rise, initiating antler growth.
By late summer, testosterone levels decline, signaling the end of antler growth. Castrated male deer do not grow antlers unless given supplemental testosterone.
Age
Antler size generally increases as a buck matures. Yearling bucks often have spikes or two to four points. By three years of age, bucks will have eight points or more. Antler growth peaks between five to seven years of age and then begins to decline as the deer ages.
Genetics
Genetics plays a significant role in antler size. Some bloodlines of deer produce bucks with larger antlers than others. This is why wildlife managers select superior bucks with trophy antlers to breed.
Over time, implementing such genetic selection can increase average antler size within a deer population.
Injury or Disease
Any injury or disease that affects testosterone production, nutrition uptake, or overall health can negatively impact antler growth. Parasites like lungworms, injuries to the pedicle area, and diseases like chronic wasting disease are examples of factors that can reduce antler size and quality.
Evolutionary Purpose of Antlers
Competition for Mates
One of the main evolutionary purposes of antlers in male deer is to aid in competing for female mates. Male deer use their antlers to assert dominance and establish a hierarchy for accessing breeding opportunities.
Larger, more impressive sets of antlers demonstrate good genes and overall fitness to females. During the mating season, males will engage in ritualistic sparring matches, locking antlers and pushing to assess each other’s strength and endurance.
The winners gain preferential access to female deer for reproduction. Thus, antlers help ensure the biggest and strongest males sire the most offspring, propagating genes for large antlers through future generations.
Studies have found a strong correlation between antler size and mating success in male deer. Males with larger antlers relative to their body size tend to dominate more breeding encounters. Females also appear to actively select mates based on antler size, preferring males with bigger antlers.
This preference drives strong selective pressure on males to grow ever larger antlers to outcompete rivals and attract the most females during the rutting season.
In some deer species like elk, antlers can grow to over 4 feet long and weigh over 40 pounds. This incredible investment of resources serves no other purpose than to win mates, underscoring how fundamentally antlers evolved for sexual selection.
Males with tiny antlers or no antlers at all are essentially at a major reproductive disadvantage compared to well-endowed males.
Establishing Dominance
Another key evolutionary purpose of antlers in deer relates to establishing dominance hierarchies among males. As social animals, deer use antlers beyond just gaining mating access to females. Impressive antlers command respect and denote status throughout the herd’s complex social structure.
Deer frequently use their antlers to spar with subordinate males to assert their higher position in the pecking order. These ritualistic confrontations help minimize dangerous fights that might result in injury.
The male with the biggest antlers is able to intimidate rivals without having to resort to actual combat in most cases. All deer in the herd come to recognize which member is the dominant alpha male, based largely on his antler size.
This ability to establish clear dominance reduces conflict and promotes stability within the herd. For example, when the alpha male eats or rests, very few subordinate deer will challenge him. And during migration or predator encounters, all members defer to the alpha male’s leadership.
This cohesive social structure centered around antler dominance is evolutionarily advantageous for the herd as a whole.
Furthermore, the male with the largest antlers often has first access to food resources within his hierarchy. This means his good genes get passed on through better nutrition as well as mating privileges.
In all, antlers evolved not just for competing for females, but also for establishing reliable dominance that creates a more orderly and cooperative deer society.
Other Interesting Facts About Antlers
All Male Deer Grow Antlers
One fascinating fact about antlers is that they are grown exclusively by male deer, bull moose, bull caribou, male elk and other cervids. Females of these species, called does, do not grow antlers at any point in their lives.
This is likely an evolutionary adaptation, as antlers require a great deal of energy to grow and may impede females from investing resources in reproduction and caring for young. In most deer species, antlers begin to grow in the spring, fed by increased levels of testosterone.
They reach full size by late summer, when mating season occurs. After this peak time of testosterone, antlers stop growing and the males shed them each winter before growing a new set in the spring. This annual cycle of antler growth is unique to male deer and allows them to display their fitness to compete during the mating ritual.
Females likely find larger antlers attractive during courtship.
Antlers Get Bigger Each Year
Another amazing fact about antlers is that they get progressively larger each year as the deer ages. Yearling male deer grow their first set of antlers beginning in spring, which are typically small and simple. The next year, the antlers will be larger and have more points.
By three years old, a buck typically has a complex set of antlers with many tines sprouting from the main beams. They reach peak size by about five years old. As deer age, their testosterone levels gradually decline, which causes their antlers to slowly decrease in size over time.
A mature buck often has impressive, massive antlers to display dominance. Hunters use antler size and the number of tines to estimate the age of a white-tailed deer.
Antlers Grow Extremely Quickly
It’s astonishing how fast antlers grow each spring and summer. One of the fastest growing mammalian tissues known, antlers can grow up to 2 inches per day during peak antler growth. For elk and deer species living in northern climates, antlers begin growing in spring when days start to get longer.
Over the next few months, they rapidly increase in size. This is likely an evolutionary adaptation to take advantage of peak food sources in summer to fuel the costly antler growth. The antlers harden by late summer when testosterone levels drop after the mating season.
Velvet, which is a soft, furry skin covering the antlers, dries up and the males rub it off on trees and bushes. Amazingly, the antlers are shed each winter, typically in December through March. The regrowth cycle then starts again in spring when a new set begins to sprout.
Conclusion
While antlers are a signature trait of most male deer, not all deer grow these striking structures. Understanding the antler growth cycle and the factors that control it helps explain why some members of the deer family lack antlers.
Female deer, young males, and castrated males typically do not grow antlers. The antlers play an important evolutionary role in competing for mates and establishing dominance hierarchies.
Hopefully this guide gave you a comprehensive overview explaining why some deer have no antlers. Deer antlers are an amazing example of nature at work.
