Can We Cull Bucks? Part 3
September 22, 2010
In the first two installments of this series, we presented results from our landmark study on antler development in free-ranging deer. For many years, biologists and hunters alike have debated the practice of culling spike-antlered yearlings from the herd. The two "camps," as one outdoor writer once described it, thoroughly mixed and permanently fixed! In other words, both thought they were right although they vehemently disagreed.
One opinion states that spike yearlings will never develop quality antlers later in life. The other supports the idea that, given a chance to grow up, spikes will indeed produce quality antlers. The two opinions arose for various reasons, but most are the result of two scientific studies that produced diametrically opposed results. The study conducted by Texas Parks & Wildlife at their Kerrville research facility showed that spike yearlings were genetically inferior to their fork-antlered cohorts.
The other study, conducted by Dr. Harry Jacobson at Mississippi State University, found the exact opposite results. Dr. Jacobson concluded that there was no correlation between a buck's first set of antlers and those he sports at maturity. Obviously, both conclusions cannot be right.
We are at a loss to explain the different results from these two studies. On analysis, both have their strengths and flaws, yet one fact is consistent with each: Both studies were conducted using penned deer. Not to criticize either study, but we must point out that penned deer face entirely different conditions than do the deer found on the average hunting property across North America.
On the one hand, penned deer are coddled all their lives. They seldom want for anything except freedom. On the other hand, they also are maintained under very unnatural, crowded conditions that can affect their physiology. That's why we decided back in 1996 to design an entirely new study that looked at antler development of wild deer. We wanted our subjects to face drought, cold, breeding stress, and constant harassment by coyotes and other predators. In other words, we wanted them to be just like wild deer everywhere.
The study was designed to not be a genetics study. Instead, it was aimed at answering one simple question: Can you look at a buck's first set of antlers and predict what he will have at maturity? In addition to genetics, the end result of what any animal grows into at maturity is also controlled by certain environmental factors.
But the Texas and Mississippi studies assumed antler size was controlled by a simple set of genes. They did not consider other genetically related traits, such as the ability to efficiently use nutrients, escape predators and compete for mates. You may have the genetics to be an NFL linebacker, but without proper nutrition you'll never even make the Pony League team!
HOW WE DID THE STUDY
As described in earlier sections of this series, our study began in South Texas in 1997 and involved capturing buck fawns and yearlings over several years on 12 different ranches.
Thanks to helicopter capture techniques developed in New Zealand, we captured over 1,100 yearling bucks alone (not including buck fawns). We then marked each buck with ear tags and tattoos and released them.
In subsequent years, we attempted to recapture as many of these animals as possible. This allowed us to measure a buck's antlers over several years to determine how he performed under natural conditions. We also obtained data from bucks harvested by hunters on these properties. (Some bucks were being culled for management purposes on some of the ranches.) It was necessary to capture large numbers of bucks, because unlike working with penned deer, the chances of recapturing a specific wild buck are never 100 percent, especially when you factor in natural mortality.
To date, we have obtained data on 1,132 yearlings, 277 2-year-old bucks, 131 3-year-old bucks, 62 4-year-old bucks, and 33 5-year-old bucks. Last month in Part 2, we revealed our findings. Basically, we found there was no correlation between the size of a buck's first set of antlers and his antler size at maturity (4.5-plus years).
We did, however, find statistically significant differences for immature bucks. When divided into two classes (3 or fewer points and 4 or more points), yearling bucks with 3 or fewer points had significantly smaller antlers at 2 and 3 years of age. This was true for all standard Boone and Crockett measurements except inside spread for the 3-year-old class. However, when these bucks reached the 4-year-old age-class, antler sizes in both groups were very consistent.
Since research has shown that whitetail bucks reach full body maturity at 4 years of age, it appears that bucks starting out with 3 or fewer points catch up by the time they mature at 4'‚1/2 years. Other researchers have hypothesized that buck fawns born late in the fawning season tend to have spikes as yearlings, while those born earlier have larger racks at 1'‚1/2 years of age.
Although we generally support this theory, there was no way to know when the bucks we captured were born. Whatever the reason, though, our data support the idea that bucks starting out with smaller antlers can produce antlers as good as those beginning their antler growing life with multiple points, if they're allowed to reach maturity.
SORTING IT ALL OUT
Now, what do our results mean to you? Let's look at some additional information. First, if we look at all the antlers from the yearling bucks we caught on one ranch in one year (see photo, Figure 1), we see that there is no clear-cut line we can draw to separate them into two well-defined groupings.
The antlers in this photo are arranged by the number of points. If we were to rearrange them by B&C score, the small ones would stay in the same ranking, but the larger ones would occur in different order. So just saying that you need to "cull" spikes is not as easy as it sounds on the surface.
Now take a look at the chart. This chart represents the percentage of yearling bucks with three or fewer points by year for the same study areas during an eight-year period. In 2000, 2004 and 2005, over 60 percent of yearling bucks had three or fewer points. In the other years, this percentage ranged from 20 percent to 30 percent. What caused these profound differences? Do genetics change from year to year? Of course not! There must have been some other factor causing these wide shifts in yearling antler quality.
We think some environmental factor, such as nutrition, is the primary factor. However, our study was not aimed at identifying the causal factor. Our future research may reveal the true culprit, but for now it is enough to point out that, quite simply, there are some years in which higher proportions of spikes and 3-pointers exist, and there are other years in which those proportions are much lower.
But think about this: If the hunters or landowners involved in the study had bought into the theory that spikes were inferior and needed to be culled, they would have killed about two-thirds of their yearling bucks during that three-year period when the incidence of spikes and 3-pointers was 60 percent. What would that have done to their overall buck population?
When we further examined our data, we found that the distribution of antler points for 1,132 yearlings clearly showed that only a small proportion of these young bucks have more than 8 points. Only 7.3 percent of the yearling bucks had 8 points or more, while a paltry 0.3 percent had 10 or more points! Buying into the "cull all spikes and 3-pointers" rule would obviously lead to disaster.
OTHER FOOD FOR THOUGHT
Although our study showed that you can't predict what a yearling buck will ultimately produce from his first set of antlers, what if we assumed that the old thinking about spikes was true, and what if we went along with the idea of trying to cull them from the herd? Using this assumption, we conducted a few population-modeling studies based on published mortality rates for each buck age-class in South Texas.
And culling every yearling buck with fewer than 10 points, 8 points and even 6 points for each simulation resulted in virtually no mature bucks left to harvest. We are thankful that hunters in areas where this culling philosophy has existed for so long are not any more efficient at harvesting bucks than they are. If they were, no mature bucks would be left on the range!
So the two-part question is this: When should you cull bucks, and is culling a viable issue for most hunters and managers in the first place? If you have a management situation in which you need to cull bucks, the first age-class offering any predictability whatsoever is 3'‚1/2. Furthermore, our calculations show that if you cull yearling bucks based on antler points alone, you will make a correct decision only 2.5 percent of the time.
If you wait until a buck is 2'‚1/2 and cull on antler points alone, you will make the right decision about 10 percent of the time. And finally, based on antler points alone, culling at 3'‚1/2 increases the probability of making the right decision about 42 percent of the time. However, if you cull 3'‚1/2-year-old bucks based on both antler points and frame size, you will be right more often than you are wrong (that is, you'll be right about 60 percent of the time). That is the best you can do.
As scientists, we constantly guard against injecting bias into our research. So, we also asked ourselves: "Since some bucks were culled during the study, did we select out the small-antlered bucks before they reached maturity?" If we had, that may have had an impact on our results. So we analyzed the data for all bucks culled from the herds by age-class, and we found no statistical difference for any antler measurement, no matter how many antler points those bucks had as yearlings. Yearlings that started with 8 points were just as likely to be culled as yearlings that started with simple spikes. Hence, we feel there was no bias in our research methodology.
Another good point arose from this research. Since there was a significant difference in antler size between our two groups for both 2 1/2- and 3'‚1/2-year-olds, and since the vast majority of bucks harvested around the country are less than 3 1/2, this information certainly does not justify the culling of yearlings. A common misconception about spikes is that they always remain spikes. Neither the Texas Parks & Wildlife researchers nor the Mississippi State researchers ever said this in their studies!
In most cases, spike yearlings will produce reasonably good antlers their second and third years. In fact, a buck that one hunter considers to be "inferior" might be a "shooter" to another hunter. In East Texas, the average buck harvested annually sports fewer than 7 points, has a 10.7-inch inside spread, and is 2.4 years of age. In some parts of Pennsylvania, there are hunters who spend their entire hunting careers trying to harvest a buck with forked antlers! So you can see that in most areas, removing yearling bucks based on the number of antler points alone would significantly reduce the number of harvestable 2'‚1/2- or 3'‚1/2-year-old bucks.
The truth is, we know of only a handful of properties and management situations for which culling of any kind is a reasonable alternative. In many regions, large numbers of bucks are harvested at a very young age (less than 2'‚1/2 years). Consequently, no matter what genetics they were born with, those genetics never get a chance to be realized.
So in our opinion, instead of getting into the very complicated issue of trying to cull bucks, landowners and hunters are far better off focusing their attention on things they can do something about, such as nutrition. And that is precisely why we have spent so much time and energy over the past 15 or 20 years writing about food source management. Once you have your deer on a good nutritional plane, you should then turn to protecting young bucks.
Genetics certainly is an interesting aspect of whitetail management, and fun to debate around the campfire. But genetics is the least important of all the factors leading to the production of quality bucks. Our studies show you have to be in total control of your bucks before you start culling. That means you either must have a high-fenced property or you must own a huge piece of land. Neither is an option for most hunters/landowners today.
We hope this series will help lay to rest some of the misconceptions about "inferior' spikes and about culling young bucks from the herd. But alas, we are realistic enough to understand that some folks will not be encumbered by facts. So the debate will probably rage on and on. Hopefully, though, this series will open some eyes and help you make some objective dec
isions with your management program!