To Cull or Not to Cull - Reasons for Abnormal Antlers in White-tailed Deer
Should you cull that buck with the odd rack?
For thousands of years deer have captivated the imaginations of humans like no other animal. This is evidenced by the numerous paintings, etchings, and rituals involving deer in nearly every culture where the two have coexisted. Not only were deer antlers used as weapons, tools, and adornment, they were revered for their fascinating shapes and sizes. This fascination and reverence remain today, with few subjects generating more discussion among deer hunters than antlers.
Antlers are wonderfully complex and unique structures. They are among the fastest growing structures in nature requiring less than six months from start to finish. They even grow faster than some cancer cells. For this reason, antlers are the subject of human medical research for cancer, osteoporosis, and limb regeneration.
Antlers vary considerably in size and shape according to age, nutrition, genetics, disease, injury and many other factors. As a result, hunters and managers commonly record, analyze, and discuss various antler criteria to determine which bucks should be harvested to meet management objectives. Debates involving whether to remove bucks with abnormal or malformed antlers also are common, especially among those involved in QDM programs.
While little evidence exists regarding the benefits of selectively removing bucks with “inferior” antlers from wild, free-ranging whitetail populations, any potential benefits would only exist if genetics were the cause of the antler abnormality. However, most abnormal antlers are not genetically based, but instead are caused by an injury to a buck’s growing antler, skull, pedicle, or body.
One of the most common causes of abnormal antler growth in deer is injury to the growing antler. During growth, antlers are covered in velvet, which is similar to human skin. However, velvet differs from skin in its ability to grow more rapidly and assist in appendage regeneration. Since antlers grow from the tip, injury to the tip of the antler can cause misdirected or abnormal growth, depending upon the timing and severity of the injury.
In general, the earlier and more severe the antler injury, the more profound the outcome. This is due to the increased time for additional antler growth before the antler matures. For example, a 3-year-old buck involved in one of my research projects at the University of Georgia several years ago damaged both of his budding antlers early antler growth. That year he produced a very short, malformed set of antlers that nearly any hunter would have considered a “cull” if viewed in the wild (Figure 1). However, the following year he produced a typical 21–inch, 10–point rack scoring over 145 Boone and Crockett points. The point here is that injuries to the growing antler generally only affect antler growth that year. As a result, countless bucks are harvested as “culls” each year that would have produced normal and generally larger (due to older age) antlers the following year.
When the injury to the antler occurs during the later stages of growth, the outcome is generally less dramatic and more predictable. There simply isn’t enough time remaining before the end of antler growth period for significant abnormal growth. For example, another one of my research bucks, a 10-year-old, damaged his antlers during the later growth stages during a “kick–boxing” match with a 4-year-old. (Figure 2). During the engagement, one of the older buck’s main beams was completely severed and the other was fractured. Both antlers remained protected by the velvet. The fractured antler beam continued growing, albeit at a downward angle. To our surprise, the severed antler reattached and even sprouted several “kicker” points. Unfortunately, this buck died before completing the next year’s antler growth cycle, though it is almost certain his main beams would not have reflected the previous year’s injury.
Injuries to a deer’s pedicle or skull also can produce antler abnormalities because the tissue responsible for antler growth extends well beyond the actual pedicle (Figure 3). This explains why deer occasionally grow antlers on other regions of their head such as their forehead, eye region, or nasal region. Under normal conditions, the “extra” antler growth tissue remains dormant and no additional antlers are produced. However, when trauma to the pedicle or area adjacent to the pedicle occurs, accessory antlers may form, though they are generally smaller and poorly developed. Common causes of these injuries include fighting during the breeding season and the loss of all or a portion of the pedicle during antler shedding.
In most cases, injuries to the skull or pedicle result in permanent antler abnormalities. As a result, the decision to harvest, or not to harvest, a buck with such an abnormality should be made on a case-by-case basis. For example, if the buck has an exceptional antler on the uninjured side (e.g., a large 5-point antler), he might be worth leaving as a “breeder buck.” This is because he has demonstrated the genetic potential to produce quality antlers and he can be easily identified by property hunters. However, if the antler on the buck’s uninjured side is less than optimum, or if there are ample high-quality bucks on the property, removal is generally recommended. In such cases, the buck is not needed for any specific purpose and therefore will only be a “freeloader” with respect to property resources.
Compared to other causes of abnormal antler growth, those caused by skull or pedicle injuries are among the easiest to identify. This is because the injury is generally restricted to only one antler and the resulting abnormal antler “sprouting” is easy to recognize.
One of the most common antler deformities observed by hunters results from a break or amputation of a deer’s front or rear leg. Many hunters are aware that injuries to a deer’s hind leg generally result in a malformed antler on the opposite side. Typically, the deformed antler is smaller than normal and irregular or curvy in shape. Commonly referred to as “contralateral deformities,” the exact cause of this phenomenon is unknown. It is thought to be related to the fact that the left side of the brain coordinates the right side of the body and vice versa. It is also thought to be an adaptation to assist with balance. Since the animal has lost balance and mobility as a result of the injury, a smaller antler on the opposite side is thought to be of some assistance.
Interestingly, injury or loss of a front leg produces a less consistent response. With front leg injuries, the antler may become malformed on the same side, the opposite side, both sides, or neither side. The most common outcome is damage to both antlers or to the antler on the same side as the injury.
With both front and rear leg injuries, the resulting antler deformities are generally permanent. As a result, the same guidelines with respect to protection or removal as described for skull and pedicle injuries above are recommended. The only other influencing factor would be if the deformity impairs the buck’s ability to survive or compete for breeding duties. If the answer is yes to either, removal is recommended.
Summary and Management Implications
This article highlights the complexities involved with selective removal of male white-tailed deer based on undesirable antlers. Since most abnormal antlers are caused by factors other than genetics, extreme caution is recommended when selecting bucks for removal based on the premise of genetic improvement. Given that even the most experienced deer hunters and managers make mistakes when selectively removing bucks from a wild deer herd, it is unlikely that most hunters are experienced enough to implement a successful selective removal program. However, educating yourself and your hunting companions on the causes of abnormal antler growth will substantially increase the odds of making the correct management decision. As with other aspects of deer management, if you have any doubts make the “correctable” decision and let the buck walk.
Brian Murphy is a wildlife biologist and CEO of the Quality Deer Management Association (www.QDMA.com). He also has been an avid bowhunter for more than 30 years.