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Hunting season brings on myriad Facebook posts featuring harvested bucks with weird deer antlers. The hunter often notes that he “culled” it to remove bad genes from the herd. Then there are the hunting shows where comments are made about harvested bucks with one side of the rack deformed. On occasion, the hunter comments that it’s good to get such bucks out of the gene pool before they pass on the poor-antler trait.
Truth is, and as science confirms, most aberrant antlers are not due to genetics. A prime example is the “contralateral effect.” For years we have known that body skeletal injury causes non-typical antler development. In this situation one antler looks normal, while the other is deformed in some way, usually smaller and non-typical in appearance. If there is an injury to the back leg, then the opposite antler is affected. It can also happen with front leg injuries. In these case, the affected antler is on the same side as the injury.
Bucks hit by cars or bucks with leg damage caused by a bullet will exhibit this phenomenon. If the injury heals, the buck will usually develop normal antlers the following year. If not, one antler will always be smaller and abnormal.
In 2005, a 15-year-old boy shot the highest-scoring buck ever killed by any hunter during the Iowa muzzleloader season. The deer, wounded by a shotgun in the 2001 hunting season, had 38 points and scored 319½. With 162 inches of non-typical points, it was an amazing buck. In 2002 this buck was a dandy. But his antlers showed the contralateral pattern: one antler was much smaller and deformed. Evidently that wound healed and in 2003 he returned to his “normal” form and in future years he became even bigger.
What causes antler-point growth from random areas of the skull?
Antlers grow from the pedicle on the frontal bone of a buck’s skull. You can get deformed antlers if the pedicle at the base of the antler is damaged during antler growth. When this happens, a buck may end up with one antler growing down instead of in the normal position. Bucks have been found with a tine twisting out of the base of the pedicle and going down the side of the head.
Crazy as this sounds, you may also get an extra antler tine growing from another place on the skull. This is caused by collagen fibers. These fibers grow in bundles at the tip of the developing antler in velvet. If there is damage in that area, when the antler starts to grow it can move these fibers to other parts of the skull near the pedicle. This can lead to non-typical points projecting from various parts of the skull.
Related: How deer see and hear
Here’s another way to describe the misplaced antler growth: There are cells on the tip of the growing antler that can be moved by some type of injury. Wherever those cells end up on the skull, you may get a third whole antler or just one or more antler tines. Usually these extra tines are near the base of the antler and grow from the frontal bone, but in rare cases, they might be as far as 4 inches or more from the base. We know these extra tines or antlers can occur because of research experiments where cells taken from the pedicle and put somewhere else on the deer’s body leads to the growth of a new antler or tine.
Injury to growing antlers can lead to abnormal racks
After the velvet antler starts growing, any injury to the growing antler can lead to abnormal points. In fact, one of the most common ways a buck can develop non-typical antlers is because of an injury when the buck is in velvet. These injuries can include a bump on the velvet, a twig cutting the velvet or an insect burrowing into it.
In the early days of red stag hunting in Europe, hunters would use birdshot to purposefully injure the stag’s growing antler to get extra tine development. The light birdshot stimulated the growth of more non-typical tines. Such shooting sometimes led to the development of lots of branches.
How do abscesses cause non-typical bucks?
Research taken from the eastern shore of Maryland, shows around 10 percent of the natural mortality (excludes hunting) of all mature, older bucks is caused by something called intracranial abscession. Intracranial abscession is a bacterial
infection of the brain that leads to deterioration of the skull near the pedicle and death. It is believed that any skin abrasion allows the bacteria to enter, which erodes the bone especially at cranial sutures. This can lead to infection and death of the buck. Upon examination of a dead buck that had intracranial abscession, you can often see pus oozing from the base of the antler or the eye socket. In some cases, there is no visible outward sign of death, and the cause of death from the abscess can only be determined by autopsy.
How and why does this happens, why is it more common in older bucks and what do abscesses have to do with non-typical bucks? The theory is that older bucks tend to die from this disease because of damage while fighting each other during the rut. Since the big guys fight harder than younger bucks, they are more susceptible to skin damage. Somehow (presently unknown), the bacteria common in forests of the East find their way into these incisions and then the infection process begins.
Related: Do bucks fight to the death?
The way this type of mortality was discovered was interesting. Researchers noted a foul odor on a few antler sheds they picked up. They also noted some sheds had pieces of the pedicle attached to them, indicating eroded bone that may have led to the dropping of the antler. In other words, the infection may cause part of the pedicle to break off while still attached to the antler, leading to the antler dropping before it normally would. They also noted the disease appeared more common in non-typical bucks. Apparently the disease causes damage to the pedicle and this leads to non-typical antlers. It also leads to infection of the surface of the brain and death. As you can imagine, if the antler breaks off still attached to the pedicle, this creates a hole through the skull to the brain. Not good.
Are there less-common cases where genetics can cause weird racks?
Though difficult to prove, genetics can have an impact on antlers. For example, the lack of brow tines on mature bucks is probably genetic. If a buck has very long brow tines, that is probably genetic. Antler beam palmation also appears to be genetically controlled, as we see bucks from one area with this characteristic year after year.
Drop tines could be genetic, but they could also occur from other causes. If a buck has one drop tine in one year but loses it the next, that’s probably not due to genetics. But if he develops that tine and keeps it every year, genetics most likely was the reason it was there.
Age is also a factor
As some bucks age, the more non-typical their antlers become. This is proven over and over again on game farms where large-antlered bucks are bred to does that have sired non-typicals, hoping to get offspring that also have huge antlers. And it works. Game farmers are able to take large non-typical bucks, breed them to quality does and get huge bucks that develop non-typical antlers. Almost surely this works the same in the wild, but to a lesser degree.
Let’s get back to the average hunter and “culling” bucks with one antler smaller and more abnormal than the other. As noted at the outset, doing this is really a waste of time and a waste of a potentially good buck. Body and velvet-antler damage is the main cause of abnormal racks, and in most cases their next set of antlers will be bigger and better.
Additional Resource: Spike on one side: genetics or injury? (QDMA)