March 21, 2022
If a picture is worth 1,000 words, a whitetail herd model is worth 2,000!
Since I’m limited to 1,000 words in this column, I’ll provide two herd models on the next page that detail the impacts of two completely different harvest strategies — mismanaged and well-managed — and let you tease out the implications for your hunting area.
Truth is, there is not a state wildlife agency in America with the ability to better understand how the local deer herd uses your Back 40 than you do. State agencies use models designed to achieve management objectives across a vast landscape, and as such, these models contain large numbers that lead to large assumptions that may not be applicable to your piece of deer dirt.
Our two herd models are simple numerical representations of the same herd. Although the herd starts out the same, these examples help you to see how it changes when two different harvest strategies are applied over the course of three hunting seasons. This allows you to see how the different harvest plans impact overall deer numbers and quality in just three years. The more you think about the numbers in each model, the more you realize that the harvest decisions you make this fall will have huge impacts on the quality of your local herd for years to come. I'll point out a few harvest decisions made by each “camp,” but I challenge you to dig deeper and play some “what ifs” with your hunting area. Every harvest decision you make has a major impact on population size, age structure and buck-to-doe ratio of your deer herd.
Both camps begin with 60 adult deer. Of those, 45 are adult does and 15 are adult bucks, giving us a starting buck-to-doe ratio of 1:3. We'll say our goal is to maintain the herd size of 60 adults so we don’t cause long-term habitat destruction. We’ve also determined we can maintain 60 adult deer, plus our annual fawn crop, in optimal condition. As we go over 60 adults, individual condition (antler size, body weights, fawn recruitment) declines.
Since fawns generally drop at a male/female ratio of 1:1, we'll strive for a buck-to-doe ratio closer to 1:1.5. To do that, we need to consider lowering our buck harvest pressure and potentially increasing doe harvest.
We naturally experience herd additions each spring as fawns are born. Some fawns die between birth and fall recruitment. So, knowing our “recruitment rate” also tells us something about our fawn loss in the interim.
While I’ve seen recruitment rates range from zero to more than 100 percent, we will plug a 50 percent recruitment rate into our model. Based on my experience on client properties, this is a reasonable average. So, in our example, 45 adult does will produce about 22.5 fawns (22 for simplicity) that survive into their first fall, with 11 being buck fawns and 11 being doe fawns. As the number of adult does in a population fluctuates, so does the recruitment rate.
It’s important to note that the recruitment rate declines in overpopulated herds as the availability of quality food declines. In other words, simply stockpiling more does will not equate to more fawns available for harvest, since every habitat has a “nutritional carrying capacity” — a fancy term for the number of deer a given property can support in optimal condition. When recruitment rates are consistently low (below 50 percent), we need to address that through increased doe harvest, improving habitat quality or a combination of both. There will be some years when weather conditions (droughts) play a major role in recruitment rates, and that “blip on the radar” will carry through with that age group and show up in a harvest several years later.
Deer are removed from any population through natural mortality and hunter mortality. For our purposes, we'll consider any non-hunting mortality (car collisions, disease, predators) as natural mortality and assume a 10 percent natural mortality rate.
Hunter harvest is where the rubber meets the road, and our models don’t lie! If you are a bottom-line person, compare the last row in each model detailing the deer herd in the fall of 2024. Which would you rather hunt?
The Bottom Line
The mismanaged herd only has one buck 3½ years old or older, while the well-managed herd has 11! After three years, the mismanaged herd has a total of 14 bucks and a buck-to-doe ratio of 1:4 (worse than what we started with), whereas the well-managed herd has 27 bucks and a buck-to-doe ratio of 1:1.33. I can assure you rutting behavior will be much more intense in a herd with a buck-to-doe ratio of 1:1.33 than it will be in a herd with a ratio of 1:4!
In the mismanaged herd, hunters clearly overharvest young bucks and underharvest does. This “traditional deer management” approach of protecting the reproductive segment (does) and harvesting any antlered buck has resulted in population characteristics that will deliver low-quality hunting experiences for a few adult bucks. While hunters in the mismanaged group may have enjoyed instant gratification by harvesting a few younger bucks in the early years, hunters in the well-managed camp were heavily rewarded for their patience as they built a population with 40 percent of bucks being 3½ years old or older!
Meanwhile, the majority of bucks in the mismanaged population are 1½ years old. After just three years, the well-managed camp “shot their way” to a buck segment that has individuals well distributed across all age classes. They've set themselves up for many great hunts going forward as they continue to improve herd characteristics.
Harvest and herd models allow us to make decisions without actually making the wrong decision in real life. Think of a financial advisor adding your retirement goals to a spreadsheet and reporting the “nest egg” available at your desired retirement age will be “X” thousands of dollars assuming an average rate of return of “X.” Are there assumptions in the model? Absolutely! Is it better to run the numbers now, with a few educated assumptions, and realize you’re not close to your retirement goals? You bet! Knowing where you stand in your 30s or 40s allows you to make the right moves to set yourself up for the golden years you’ve always imagined! Likewise, if your goal is to harvest more, larger or older whitetails, now is the time to start modeling your herd for many successful hunting seasons in your golden years.