How to Properly Cull the Herd — Part I
March 15, 2017
It happened one fall day back in the 1980s, just as we were starting to make progress in getting folks to manage deer on private lands.
Here in East Texas, among our "first adopters" of progressive management were the many timber companies that leased out their land for deer hunting. And so, as I was refueling my truck in Alto, Texas, I bumped into the regional forester of the second-largest company in Texas, along with his wife. Both were decked out in hunting gear.
"You're really going to be proud of us," my friend said as they pulled up in their truck. "We both killed perfect cull bucks this morning!"
I asked where the bucks were and was informed they'd been taken to a deer processor only a few blocks away. Naturally, I wanted to see these terrible offenders of good deer genetics, so I jumped into my truck and followed the couple to the locker plant.
When we got there, the cooler door swung open to reveal the bodies of two bucks lying side by side on the floor. One was a spike, the other an 11-pointer: both yearlings sporting their first racks. I congratulated the two hunters on their kills and went to my truck — where I mentally threw up!
Selling Management Concepts
Since those early days of private-land management, we've made a great deal of progress in many areas. Of particular significance has been the increased protection of young bucks.
In the early 1990s, North American Whitetail's financial support of a landmark study on antler restrictions in Dooly County, Georgia, was instrumental in bringing some folks around to the idea of protecting yearlings. Making bucks with an outside spread of under 14 inches off limits resulted in nearly all yearlings being protected. It also protected many 2 1/2-year-olds. Over time, the rule increased the number of older bucks. In the quarter-century since, modified forms of this strategy have found their way into use across much of North America.
The percentage of yearling bucks in the continent's overall harvest is now far lower than it was even a decade ago. However, the one area in which we've made little progress has been in changing the perceptions of hunters and managers about genetics and culling. Let's look at what scientific research has revealed on that topic.
First of all, the verb "cull" means to remove unwanted individuals from the population. This includes both bucks and does. Shooting the right number of does to control herd growth is the most important part of culling the herd. In fact, it's the single most effective herd-management tool we have, provided it's used properly.
On the other hand, culling bucks perceived to be genetically inferior isn't nearly as important. Unfortunately, many hunters use the idea of improving herd genetics as an excuse to kill specific bucks that otherwise didn't qualify for harvest under a given property's stated management guidelines.
At our Institute for White-tailed Deer Management & Research, landmark antler research on free-ranging deer over almost two decades has, in my view, once and for all settled the argument about spikes. What we learned is there's no relationship between a buck's first antlers and those he'll grow when mature; a spike is just as likely to end up a high-scoring trophy as one that has eight or even more points as a yearling.
It seems intuitive that a yearling with more or less than the average amount of antler on his head will continue that trend throughout his life. But our data from thousands of wild bucks captured with helicopter nets and then recaptured years later show this isn't the case.
Of course, there are exceptions. I'm talking about yearling spikes, not those 2 1/2 or older. (These exist, but they're very rare.) So there's no reason or excuse for culling any buck at age 1 1/2.
I go by the saying, "Every Boone and Crockett buck once was a yearling." How many times over the last decades has a yearling buck been taken from a property in the back of a pickup three or four years before he'd have become a record-book qualifier? Today's widely used antler restrictions — some more effective than others — have made a significant difference in improving age structure in many herds. Therefore, culling shouldn't involve removal of yearling bucks — pure and simple!
The antlers any buck carries are the result of the interaction of his genes and his environment to that point in life. Regardless of genetics, he grows up under a set of conditions that might or might not ever be fully repeated. That's why actual clones of a monster buck don't all grow up to look exactly like him.
So we can't look at a buck and divine all that much about his antler genetics. In attempting to cull, we're relegated to looking at the phenotypic appearance of his antlers. Phenotype is the outward expression of genetics as a blend of genetic potential and environmental reality. Nutrition plays as big a role in antler quality as genetics. So at best, we're left with making assumptions that could be wrong in many cases.
The Law of Average
If we could capture every mature buck on a large property and measure their antlers, the resulting numbers would be a normal, or "bell-shaped," curve. Almost everywhere, the peak of this curve would show the "average" typical buck has eight points and around 130 inches of antler score. (Average score is lower where very small-bodied adult deer are the norm, such as with Coues subspecies. For these diminutive deer, we must calculate a different curve with about a 90-inch average. But the "8-130" rule applies to most other subspecies.)
Our antler study also showed that only 12-15 percent of the thousands of bucks captured as fawns and yearlings ever broke 150 inches of gross score in their lifetimes. Bucks that broke 160 inches made up fewer than 1 percent of the total. So you can imagine how many zeros to the right of the decimal it takes to calculate the probability a given yearling ever will achieve a gross score of 170. And our study was done in some of the better trophy areas of South Texas, which have a history of B&C qualifiers.
What we have to consider in any culling program are the two ends of the tails of the normal curve. The fringe individuals represent the best and worst bucks, in terms of antler size. The vast majority of the "middle ground" bucks are, by definition, average.
So...What Should You do?
If a buck we shoot comes from one of the tails of the graph, his removal has a greater impact than if he's one of the much larger number of average specimens. But in a free-ranging population, a single buck doesn't breed that many does anyway. So even if he has poor antler genetics, culling him rarely has much genetic impact on the herd. It's really more of a "feel good" activity than anything else.
But let's say you still want to try to improve antler genetics through culling. If a buck is needing to be culled, at what age should it be done? For that matter, how do you know you're looking at bad genes instead of malnutrition or injury that's resulted in "inferior" antlers? We'll look at these questions, and several others concerning culling, in the Spring issue.