New Texas Deer Study Produces Surprising Results

A new book summarizes and explains 15 years of intensive research on South Texas deer.

“Advanced White-Tailed Deer Management: The Nutrition-Population Density Sweet Spot,” was produced by a group of top researchers who set out to find what combination of supplemental and natural nutrition and whitetail population density would produce the largest antlers on bucks without harming vegetation — finding the “sweet spot.”

The research was conducted through the Caesar Kleberg Wildlife Research Institute, led by Timothy Fulbright, Charles DeYoung, David Hewitt and Donnie Draeger, and assisted by 25 graduate students.

Now called the Comanche-Faith Project, the research is the first of its kind in the semiarid South Texas environment with frequent droughts.

Chapters in the book’s 164 pages include detailed information on vegetation response to increasing density and supplemental feeding, antler characteristics with increased deer density, and deer diets with increased density and supplemental feed.

Some of the results weren’t as expected, even for experienced researchers.

Vegetation and density

With respect to reducing deer numbers to improve diet quality for the remaining deer, the study showed that principle doesn’t necessarily work in South Texas.

“Harvesting deer to increase diet quality in semiarid South Texas is seldom necessary,” the book concludes. Noting the study areas were devoid of domestic livestock and feral hogs, the research found the vegetation was not materially impacted by an increase of deer density to one deer per five acres on the areas studied.

“Increasing deer density did not decrease first-choice plants in the habitat or increase second and third-choice plants, and supplemental feeding did not decrease first-choice plants,” the book states. “Increasing deer densities did not result in dramatic changes in vegetation when high-quality supplemental feed was available year-round.”

Possible reasons given were that heavy browsing during drought years is usually temporary and the native shrubs replace browsed parts through regrowth in wet years.

Antler quality and deer density

Deer managers have speculated that decreasing deer density would help antler scores for the remaining bucks.

Even in areas with supplemental feeding, antler scores in the same bucks still vary from wet years to dry years.

“A buck is more likely to have larger antlers in a wet year than a dry year,” the book reports. “A buck that meets your criterion for a “management” buck in a dry year might be a “trophy” in a wet year.

However, the research did not fall in line with the theory that antler scores increase when density decreases and vegetation improves.

“Deer population density had no effect on the gross Boone-and-Crockett score of mature bucks with and without supplemental feed,” the studies concluded.

Harvesting does

Southwest Texas is not an area where harvesting does is helpful, the book concludes.

“There are many cases when harvesting does makes sense; but in the semiarid, highly variable environment of our study area, doe harvest is either unnecessary or detrimental in the absence of supplemental feed,” the book reads.

So what is the “sweet spot?”

“Our assumption at the beginning of our study was that the sweet spot would be the population density at which antlers were largest and vegetation was unharmed,” the book reads. “We did not anticipate that increasing density would not affect antler size and other measures of deer performance, or that deer diets would be almost entirely supplemental feed at the highest deer densities.”

The conclusion was the anticipated “sweet spot” probably doesn’t exist, at least in a one-size-fits-all prescription.

“The keys for large antlers are supplemental feed and rainfall, regardless of deer density,” the book states.

Therefore, economics, such as the cost and logistics of feeding, may be the driver of finding the sweet spot.

During the study, researchers spent roughly $100,000 per year on feed for 2,000 acres with one feeder per 50 acres, at a cost of approximately $40,000 just for the feeders.

“In southwest Texas, the availability of high-quality food depends on precipitation and the type and amount of supplemental feed,” the book concludes. “Precipitation and supplemental feed influence the availability of high-quality food and antler growth in bucks more than deer population density.”

The book makes an excellent reference for landowners and managers in South Texas and beyond, gaining understanding of the relationship of vegetation, nutrition and deer density. It is available for $35 through Texas A&M University Press.