Spikes and the Antler Equation
(En anglais seulement)
By: Ben Koerth and Dr. James Kroll
"There he goes!" was the cry as the buck ran across the road into a narrow clearing on the other side. Hard behind the buck the helicopter swooped in low and fast over the brush, followed by the clear boom of a gunshot in the morning air. Literally within seconds of that first sighting, the buck was down and being loaded by eager hands into the back of a pickup truck.
No, despite your first thoughts, this is not a tale of illegal hunting. Rather, it¹s an introduction to an important research study we are conducting on antler growth in wild whitetails. The gunshot was not a normal gunshot. Rather, it was from a specialized gun that shoots a net instead of a bullet. Combined with a helicopter to rapidly find and approach a deer, we can quickly and precisely capture individual deer for marking and measuring before releasing it unharmed at the capture site - all very important aspects of the study described herein.
The basis for the study is an age-old controversy that has, so far, evaded being solved by even the best whitetail biologists in the country. Future antler growth of white-tailed deer that have spike antlers as yearlings versus yearlings with three or more points as their first set of antlers, has been a particular point of contention among deer hunters and managers for many years. Results of various studies on captive whitetails have produced recommendations ranging from removing all spike-antlered yearlings as inferior individuals to complete protection of all yearling deer no matter the amount of antler growth in their first year. Inferior, in this case, refers to an animal that has less potential for future antler growth than other members of the same age group do.
In trying to grow the highest quality animals, only the animals believed to have the greatest potential for good antler production are desired. If an antler type with low growth potential can be identified at an early age, intuitively it would seem a good idea to remove those animals before they make a substantial contribution to the breeding population. The genetics for poor-quality antlers would not be sustained in the population. The question is, can this really be done?
Over the years, numerous studies have been conducted on the predictability of antler growth in whitetails. Results of the two most well known studies seem to conflict. Studies at the Kerr Wildlife Management Area by Texas Parks and Wildlife Department personnel suggested that spikes on yearling whitetails may be an antler type with low potential for antler growth at maturity. Thus, their recommendation is to cull spikes as a management tool to increase average antler size of bucks in that age group as they grow.
At the other end of the spectrum is a well known study done by Dr. Harry Jacobson at Mississippi State University. Dr. Jacobson asserted spike antlers on yearling bucks could be related to many factors including age (when during the fawning season a deer is born) and nutrition. Results of the Mississippi State study indicate spike antlers could not be used reliably to judge antler growth potential. Therefore, culling of yearling bucks based on antler criteria would have little positive impact on average antler quality in the future deer herd and would simply result in fewer bucks available for hunting.
A primary drawback in both studies is that they were conducted with captive deer. It often is difficult to take results from confined animals with a known history and fed a high-quality diet and apply those results to animals born and raised under a wide variety of range and management conditions. Research similar to that conducted on captive deer needs to be done on a larger scale with free-ranging deer populations similar to the ones we hunt.
While that sounds great on paper, studies of this nature are not easy. One of the biggest problems in studying free-ranging deer is being able to positively identify a large number of known-age animals. Also, you have to be able to handle the animals in a manner where measurements can be taken from the same deer from one year to the next. Believe me, that is no easy task.
The net gun method allows easy and safe handling of animals after they are entangled in the net. Once the animals are captured, we affix a color-coded ear tag that is individually numbered. The color of the tag tells us instantly the age of that deer when seen again in the future. We also tattoo a number corresponding to the ear tag on the inside of the ear in case the ear tag is lost. Antler measurements can be taken quickly and the animals released unharmed at the capture site. In a nutshell, that is the study and the methods we are using to accomplish this task.
By its nature, this is going to be a very long-term study. A large number of yearling bucks have to be captured so we can measure their first set of antlers. In just three years, we have captured and tagged 444 bucks over a three county area in South Texas. These same bucks will need to be repeatedly trapped in future years to measure the antler growth. Also, we are capturing new bucks each year along with recapturing bucks caught in previous years. In this way, we will have a sample of animals that are born and raised in different years in a variety of weather and range conditions. At this point, we are only three years into the project. As such, we are not in a position to make positive conclusions about anything. The point of this article is to introduce the research so you can see what we have found so far and be able follow along as the study progresses.
However, even with the short time period so far, some interesting trends are being revealed. Whether these trends hold throughout the remainder of the study remains to be seen. Nonetheless, these initial results may give you something to think about next hunting season. For many hunters, one of the most important criteria in antler quality is the number of points. So let¹s look at the development of antler points from the yearling bucks we have captured and how they progress through various ages. From our data, if you plot the number of antler points bucks had as yearlings against the average number of points those same bucks had the next year you will see that the yearlings with the fewest antler points still had fewer points as 2-year-olds. Yearlings with two or three points on their first set of antlers averaged about eight points as 2-year-olds. On the other end of the spectrum, yearlings with eight or nine points on their first set of antlers were 10-pointers on average the next year. The middle group, yearlings with four to seven points, averaged about nine points the next year. On the surface this appears to support the contention that spike-antlered deer may be inferior and on average will never produce the kind of antlers that multi-pointed yearlings will.
However, remember these are really young deer with a lot of growing left to do. Another way of looking at the data is to compare the amount of growth each group put into antlers their second season. If you plot the number of antler points that bucks had as yearlings against the percent of antler growth change in their second set of antlers, there appears to be somewhat of a different story. The little guys were kicking butt by the next year. Much more energy appeared to be expended toward growing larger antlers by yearlings that started small. A yearling that starts with nine points and goes to 10 the next year is a small change. However, going from a spike to an 8-pointer is a tremendous change. Still, a 10-pointer is better than an 8-pointer, right? If a yearling started with spikes or three points and only averaged about eight points the next year, that¹s still smaller than yearlings that started with eight or nine points and averaged 10 points on their second set of antlers. It doesn't matter how much energy they put into antler growth if they¹re still smaller. Is there some credence to the claim that small-antlered yearlings will never be as good as yearlings that start with a better set of antlers?
Let's fast-forward to year three and compare the average antler points those same yearlings had on their third set of antlers. If you plot the number of antler points that bucks had as yearlings against the average number of points those same bucks had as three-year-olds you will see that the yearlings with few antler points have caught up. Yearlings that started with spikes averaged just as many points as yearlings that had many more points on their first set of antlers. There are minor differences in the average number of antler points as three-year-olds, but basically there appear to be no real differences no matter the number of points a yearling started with.
By the third year, data from our wild-trapped bucks seems to agree more with the results of Dr. Jacobson and the Mississippi State study. Yearling bucks with small antlers seemed to have just as good a chance of turning into a good deer by their third year as the yearlings with larger antlers did.
Now, we realize there is much more than simply the number of points that make a high-quality set of antlers. However, this indicates the trends in the data we have seen to this point. As we stated earlier, this study is still in progress and the final results may lead us in a totally different direction. However, our results in the study so far show there is no indication that the size of antlers on yearling deer is a good predictor of what a buck might grow in the future if allowed to mature. Some other interesting aspects from the study we have found so far are that the number of spikes in a herd varies from year to year and can be affected tremendously by weather conditions - specifically rainfall. This is especially true in drought-prone areas like south Texas. Comparing data between years on the number of spikes and 3 pointers on a single ranch where we captured bucks is quite revealing. In 2000, 23 percent of the yearling bucks were spikes. If you add in 3-pointers, 33 percent of the yearling age class had three points or less. While not a great rainfall year, it certainly was better than the next year.
In 2001, with even less rainfall, 53 percent of the yearling bucks were spikes. Again, if you add in 3-pointers, 64 percent of the yearling age class had three points or less. The number of spikes and 3 pointers essentially doubled in one year. The genetics didn¹t change in one year, but the average antler quality of yearling bucks sure did. If you were in a program that culled spikes and 3 pointers as inferior deer, you would have lost nearly two-thirds of that age class in the low rainfall year. Think of how many bucks that would leave you to hunt in a few years.
However, we don¹t want to lead you to believe that we think culling is not a worthwhile management practice. We still contend you can change the average antler quality of a well-managed deer herd by culling bucks with inferior antler quality. However, results of this study so far support our long-standing contention that culling should be done only on the older age classes of bucks - never on the yearlings. Young bucks, especially yearlings, are just too sensitive to weather and growing conditions to give you a good idea of the kind of antlers they are capable of growing in future years.
Also, an effective culling strategy not only involves removing bucks with perceived inferior antler quality, but also includes removal of females. An adequate doe harvest allows you to control the overall population, manipulate the age structure and remove the less productive females from the herd. In the long run, there really is only a need for enough females to produce the annual crop of bucks and replacement females. Usually, this is far fewer females than many think. Early in a management program, we feel you should remove the older age does. This results in an immediate reduction of the population and significantly lowers the average age of females left in the herd. Also, younger does usually produce fewer fawns, so maintaining control of the population is not as difficult in the future. As time goes on, having a young doe age structure allows you to better take advantage of improving nutritional conditions and overall genetic makeup of the remaining herd. If you have been doing a good job of culling bucks, the younger does are the ones most likely to have been conceived by the higher antler quality bucks you have left to breed. Thus, the offspring potentially have higher genetic quality than their parents and are more likely to pass on those quality genetics to their offspring.
There are few issues that have created more controversy than the culling of spikes. While we still do not have the definitive answer, results of our study should increase our understanding of antler growth in free-ranging whitetails. At this point, it appears that culling of yearling deer, no matter what they produce as their first set of antlers, may not be a good idea.