By Dr. Grant Woods
I recently shared in a column that big antlers start in the dirt. Let me explain that another way: deer with a healthier diet produce larger antlers, no matter where they are living. This may seem contrary to a principle most biologists were taught in school called Bergmann’s Rule. This principle states that for critters that are broadly distributed, the ones living further away from the equator typically have larger body sizes.
Bergmann’s Rule generally holds true for whitetail deer. Deer in the Northern states typically weigh more than deer living in the Southern states. During the early 1990s, I collected lots of data from deer in New York’s Adirondack Mountains. There were almost no food plots in this vast area and very little timber harvest due to government regulations. Simply put, there wasn’t much quality grub for Adirondack whitetails.
During the same period, I was doing a lot of fieldwork in several Southern states. We collected biological data from literally hundreds of deer that were 1,000 miles or more south of the Adirondack Mountains. The Southern projects were primarily on properties with good food-plot and timber-management programs. Even though the Northern deer were living in an area of poor habitat and the Southern deer were living in an area of good habitat, the average body weight by age class was higher for the deer living in New York. In this case, Bergmann’s Rule seemed to hold true.
Body Size vs. Antler Size
But body size isn’t always related to antler size. An easy example is seen in the bucks from South Texas. Even though many ranches in South Texas have aggressive supplemental feeding and habitat-management programs, in general average body weights for each age class of deer in South Texas is substantially less than for whitetails from the northern part of their range.
Despite that, most hunters know that South Texas produces more than its share of large-antlered bucks! This is easily confirmed by viewing the Boone and Crockett Club’s map of whitetail record-book entries.
The same trend was true based on the data from my projects in northern New York and in the Deep South. In fact, the average antler size for bucks from the South was larger than those from the Adirondack Mountains for the same age classes! This was most likely due to the difference in habitat quality.
The bucks from the Adirondacks had access to an ample quantity of low-quality food. The primary food source was hardwood browse. Clearly, a significant factor that determines antler size, based on my work, is the quality of the buck’s diet. In addition to my work, Drs. Bronson Strickland and Steve Demarais from Mississippi State University have found the same trend based on analyzing data collected by several state and provincial agencies throughout the whitetail range.
They reported the findings from 74 locations across the whitetail range to the Quality Deer Management Association (www.qdma.org). Their findings from this large dataset showed that “body size generally conformed to Bergmann’s Rule.” That is to say that the average body size of whitetail deer increases as distance from the equator increases.
However, they found a weak relationship between antler size and latitude. In fact, Strickland and Demarais sum up their findings by saying:
“Deer from northern latitudes do have the framework to be larger because antler size and body size tend to be related. However, the map clearly shows that deer habitat (in this case, soil quality and food) can have a bigger impact.”
Better Food for Bigger Racks
Their work and mine show the same trends. This is great news for hunters! The take home message is that no matter where you hunt, quality herd and habitat management can result in producing larger-antlered bucks than the average for the area! This research also serves as a call to have realistic expectations. If you are hunting an area where the forage quality is low, don’t expect most bucks to produce large antlers for their age.
I started this series by saying, “Simply having a warm-season food plot doesn’t ensure quality forage for the deer where you hunt. This is primarily because plants are simply nutrient transfer agents. That is to say, plants transfer nutrients from the soil and air to the critter that consumes the plant or back to the soil if the plant isn’t consumed, decomposing back into the soil. Either way, plants are simply nutrient transfer agents. To have the best deer in the neighborhood you must have the best food in the neighborhood!”
The antlers you will see this fall are a product of what that deer consumed long before hunting season started. No matter where you hunt throughout the whitetail range, you can work toward improving the soil to allow the herd to produce larger antlers.