Antler Abnormalities in White-tailed Deer


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Antlers have fascinated me since I first observed a white-tailed deer buck, and more so later, as I admired other antlered members of the deer family. These “mystical” appendages have intrigued scientists for hundreds of years because antlers are such an unlikely feature from an evolutionary standpoint. It goes without saying, that hunters have also long been awestruck by the antlers of their quarry. The quest to acquire large or unusual examples of these external growths of bone, peculiar to the deer family, seems to have become an unrelenting and expensive pastime for many. It follows that a fascination with antlers would also support a fascination with unusual or abnormal antlers.

antlers-1.jpgThere are three possible causes for the various abnormal antlers we often observe in white-tailed deer. Abnormalities can arise from: 1) genetics or heredity; 2) internal malfunctions within the body of the deer or, 3) some type of direct injury to the deer or the antlers. Unfortunately it is not always possible to distinguish clearly among these causes. Most often hunters who observe or kill a deer with abnormal antlers leap to the conclusion that genetics, more specifically “bad” genetics, is responsible.

Once again genetics or heredity is the least likely explanation for most malformed antlers. Mechanical injury to the antler and sometimes to the body of the deer accounts for most abnormalities we see. Probably more than heredity, but still way down the list of probabilities, is some “internal” problem that has resulted in abnormal flow of hormones, especially testosterone, in the particular individual.

Since injury produces most abnormalities, let’s focus on this issue more than the other two. As regards injury, the most difficult to explain is the occurrence of a malformed antler on one side of the head which is opposite the injured side of the deer’s body. These situations most often are associated with leg injuries, and the antler abnormality may continue for successive seasons especially if the injury results in a permanent limp or loss of leg or foot. This happens but is not easily explained.

The growing antler is especially susceptible to injury and these injuries often lead to strange and exaggerated growth to the injured antler and sometimes to the uninjured side as well. Antler injury accounts for many of the wild-looking “nontypical” racks we see  and read about. These injuries, especially if they affect the pedicle (also called the “growth platform”) for the antler, can produce exaggerated size and growth to one or both sides. This “non-typical” growth can occur for several years after the initial injury. However, it does not preclude recovery and a return to normal growth sometimes later on.

antlers-2.jpgAntlers fractured during growth often heal but grow off in unusual angles. If a break is clean there can be growth of one or more points to the severed antler tip sometimes producing a rosette or crown of points. Should a buck damage one or more of the velvet antler tips after development is well along, we often see what has been called an “acorn” tipped antler. In acorn tipped antlers the tip or tips develop enlarged knots on the end that usually terminate to a point that is shaped like an acorn with its rounded body and sharp tip furnished by the acorn cup or the bottom of the acorn itself.

Over the past decade the most common observation reported to me has been the “half-rack” deer. The “half-rack” is an individual or individuals with one normal side and one malformed or nonexistent side caused by injury to the “bad” side. This type injury is so common that sightings of several different individuals with similar injury patterns on a given hunting area leads to the “genetic” conclusion. Not so. Why? Genetic or hereditary antler changes resulting from random mutations almost always affect both sides and are most often associated with antler shape and form. Many hunters looking for a reason to kill more bucks will cull these half-racked bucks in the belief that they’re helping the herd’s genetics. In my mind this action is neither good or bad. It may be “bad” if there are already far too few mature bucks in the herd.

antlers-3.jpgRandom mutations affect antler size and shape most often and may account for “high, tight” racks in a given area, or the extremely wide, short-tined racks found in other areas. Palmation of both sides of the antlers may be genetic but it is not necessarily a dominant gene. However, it must have been in moose, caribou, and fallow deer, huh? Finally, let’s examine “internal” or systemic reasons for abnormal antlers.

Abnormal antlers most often result from some injury or disease that changes normal hormone levels in a deer, especially testosterone. Castration of bucks results in the rather immediate shedding of any current antler growth and the regrowth of a permanent velvet antler set. This permanent antler set grows each year and combined with injuries, especially partial freezing in colder climates, can produce grotesque, tumorous growth about the deer’s head. This is unusual but does happen.

Endocrine (hormone) imbalance also can account for antlered females and antlerless males in whitetailed deer. Of course the presence of antlers in female caribou and reindeer is genetically caused. Antlers in female white-tailed deer can occur with variable frequency, reported in scientific literature from 1 in 900 to 1 in 4500. It is not that rare. Most often antlered females, for some reason, have just enough testosterone to stimulate antler growth but not enough to complete the velvet-shedding process. Therefore most, but not all, antlered females have simple spike, velvet racks. On occasion females with polished and branched racks are observed. Often the presence of antlers does not affect reproduction in the affected doe. There seems to be no consensus on whether these antlered does shed and regrow antlers each year, but since most have velvet racks one would suspect that they are permanent like those of castrated bucks.

Antlerless male white-tailed deer do occur but seemingly less frequently than antlered does. In two species of deer, the musk deer and the Chinese water deer, males are antlerless, obviously for genetic reasons. In European red deer (actually a species of elk) antlerless males occur with enough frequency to become named “hummels.” There is no clear explanation for such events but it appears to be related to the “polled” condition in cattle. In white-tailed deer, under experimental conditions, it is exceedingly more difficult to prevent antler growth in males than to promote it in females.

It is always good to remind our readers that biological systems are full of surprises and exceptions. We can never be absolutely sure about anything. In the case of abnormal antlers in whitetailed deer we have offered the “most likely” explanation. In nature, the simplest explanation is usually the most likely

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