As one of the most impressive structures in the animal kingdom, antlers don’t exactly have a simple growth pattern. Consequently, asking when they grow is a more complicated question than it might seem. Not only do antlers have a yearly cycle to their growth, but growth varies depending on the age of the deer and environmental factors.
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What Time of Year Do Antlers Start Growing?
Bucks start growing their antlers in the spring after having shed them in the winter. A good rule of thumb is April 1, but many deer will already have antler buttons in late March, and some later bloomers may not start growing until late April. The antlers grow over a period of about 120 days or four months.
The new antlers are covered in velvet and can grow over an inch per day, making them one of the fastest growing bones among mammals. Their final size will depend on the buck’s age and health as well as environmental factors, but when it reaches this point in the late summer, usually the end of August, the buck will shed the velvet, and debut the hard, calcified antlers.
This yearly cycle follows along with the buck’s yearly testosterone cycle. After the rut in the fall, his testosterone will drop, so he’ll shed his antlers. By the spring, his testosterone will start to rise again, so he’ll start growing new ones. At the end of the summer, the testosterone peaks significantly in preparation for the rut, so he sheds the velvet.
This hormone cycle itself is regulated by sunlight. The lengthening days in the spring prompt the beginning of the cycle while the shortening of the days in the late summer prompt its end.
When Do Bucks Start Growing Antlers?
Antlers are a secondary sex characteristic, so they can only grow when the animal has adult levels of sex hormones, specifically testosterone. Think of antlers like the deer version of a beard.
Of course, deer have much shorter and more condensed lives than human beings. They go through puberty much faster. In fact, fawns born in the spring are more often than not capable of mating the coming fall.
As a result, newborn male deer are usually capable of growing antlers their first year of life. These are far from the glorious mounts you want for your hunting lodge, though. In fact, they’re usually just little bumps of bone, leading to the term “button buck.” Think of it as the first fuzz above a teenage boy’s lip.
It won’t be until their second cycle that a “yearling” buck is capable of growing full antlers. Still, most don’t, only growing spikes that reach about 25% of their potential growth. Similarly, these are often called “spike bucks.” It’s not until a buck’s second year that he’s likely to grow large antlers more than half their potential size and differentiated into points, or tines.
Deer Age and Antler Growth
Arguably the largest factor affecting a buck’s antler growth is his age. As he matures, his antlers will increase in size, usually reaching their full potential in his seventh antler cycle when he’s 6-½ years old. From this point he will mostly grow the same, maximum-size antlers for two or three more seasons until he is 8-½, after which his health and dominance will begin to decline. The antlers will shrink in size and may develop abnormal, asymmetrical shapes and a weathered appearance.
This describes general deer antler development by age.
|Buck Age (years)||Percentage of Maximum Potential Antler Growth||Description|
|0.5||10%||“Button bucks” with only small buds of bone growth from their heads|
|1.5||25%||“Spike bucks” with longer antlers still limited to single points|
|2.5||60%||Antlers begin differentiating into tines and are as wide as the ears|
|3.5||80%||“Mature bucks” whose antlers will have thick beams and differentiate into multiple tines|
|4.5 – 5.5||90 – 99%||Antlers will continue growing and may gain more tines|
|6.5 – 8.5||100%||“Dominant bucks” who, if they live this long, have reached their maximum antler potential|
|9.5+||<100%||Few bucks live this long, but those who do are elderly and begin seeing a decrease in antler size|
What Environmental Factors Affect Antler Growth?
Furthermore, deer only grow antlers when they’re healthy enough to do so and have the nutrients to build them. A starved deer will likely not grow antlers at all or will at least grow antlers much smaller than their maximum potential.
Some nutrients can make an incredible difference.
Protein is arguably the most important nutrient necessary for a big rack. Bucks need access to high-protein foods during the spring and summer to keep up with the fast growth. These include soybeans, alfalfa and clover.
An active deer needs anywhere from 16-20 percent of its food to be protein. Studies have found that a four-year-old buck eating just eight percent protein could experience a whopping 20-inch decrease in antler size.
The minerals most important for growing antlers are those most important for growing bones in general: calcium and phosphorus. It’s just that, with over an inch a day of growth, antlers need a lot of it. Mature bucks need phosphorus levels upwards of 0.3 percent and calcium levels upwards of 0.5 percent. Deer with a phosphorus deficiency have been known to actually eat bones.
Deer also need salt to stay healthy and have to keep a proper balance between sodium and water. This is why salt licks make great bait and are an important part of your herd management plan.
Last but not least, a buck simply needs calories to be able to grow his antlers. Adult deer need about 131 calories per kilogram of bodyweight just to make it through the winter. An average buck weighs about 150 pounds, or 68 kilograms, so that’s nearly 9,000 calories per day. To grow antlers in the summer, he’ll need excess calories, so access to high-energy grains and grasses is essential.
How Do Genetics Affect Antler Growth?
Finally, a deer will only grow antlers if its genetics code for them. The size and even existence of a buck’s antlers may depend on his age and nutrition, but this is all within a potential maximum determined by his DNA.
Of course, the biggest genetic factor is sex. Normally, only male deer grow antlers. However, there are some exceptions. Still, even within the male population, there is a big variation in the size and shape of antlers as a result of their unique genetic codes.
In fact, the complex DNA in combination with environmental factors and age means that no two sets of antlers are exactly identical, making them all the more majestic.