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Deer World

TPWD biologists at Kerr Wildlife Management Area have helped make Texas the epicenter of white-tailed deer research.

By Russell A. Graves

For Texas deer hunters, these are the good old days. Of all the game species in the state, white-tailed deer are the most biologically successful. From an estimated population of 232,000 in 1938, white-tailed deer now flourish. Currently, the Texas deer herd numbers about 4 million animals and holding steady, and 529,854 hunters harvested 436,942 deer during a generous two-month-long season last year. A productive, healthy deer herd in Texas is a boon to small-town businesses across the state. More than 500,000 hunters make an enormous impact on the Texas economy. In 2001 (the last year that data were collected), the economic impact of deer hunting in the state was just more than $690 million.

As a result of contemporary management strategies, Texas ranks fifth in the nation in the number of Boone & Crockett class, trophy white-tailed bucks recorded, and the state is a premier destination for whitetail hunters nationwide. During the last 25 years, the number of Boone & Crockett record book entries (196) from Texas surpassed, by 20 animals, all the entries from 1892 to 1979 combined.

Much of the phenomenal growth of Texas white-tailed deer populations can be attributed to the Donnie E. Harmel White-tailed Deer Research Facility at the Kerr Wildlife Management Area. Situated 10 miles from the town of Hunt at the edge of the Hill Country on the Guadalupe River, this WMA is the birthplace of deer research by the Texas Parks and Wildlife Department. The lessons learned here have improved the quantity and quality of deer not only in our state, but also nationwide.

When I visited the Kerr WMA, I was greeted at headquarters by TPWD biologist Bill Armstrong, an affable man with an encyclopedic knowledge of the area and the deer research conducted on the premises.

“Our main research focus here at the Kerr Wildlife Management Area is to promote healthy land with a healthy deer herd,” explained Armstrong. “One of the key things we’ve learned over the years is that you can manage for both a healthy piece of land and a healthy deer herd through management of the ecosystem. By using a combination of fire, livestock grazing, deer numbers and controlling the deer and cattle’s use of the range, we can maintain a healthy habitat for a number of species.”

The Kerr WMA is a study in land reclamation. Purchased in 1950, the original 6,493 acres were severely overgrazed by deer and domestic livestock and lacked substantial plant diversity. Through prescribed burning, brush control and improved grazing systems, managers at the Kerr WMA encourage healthy plant growth and demonstrate the compatibility of domestic livestock with wildlife. By holistically managing livestock, wildlife and the rangelands as parts of an interconnected system, weaning weights of calves at Kerr WMA have increased an average of 130 pounds since 1968, while the field-dressed weights of white-tailed deer have shown a substantial increase as well.

Since 1977, some 50,000 people have toured the WMA and learned of the Kerr’s ecosystem approach to managing the land. With ranchers and land managers implementing the lessons learned at Kerr over the past quarter-century, Texas deer lands have been the most productive in history. A side benefit of the rangeland work is that researchers in the area can study the effects of land management practices on endangered species such as the black-capped vireo, the golden-cheeked warbler and the Tobusch fishhook cactus.

In 1973, the Texas Parks and Wildlife Department constructed a 16-acre research facility to study white-tailed deer physiology with an emphasis on the roles of genetics and nutrition on antler size. Since antler size is an important indicator of a buck’s age, this study helps achieve the primary goal of creating a stable age distribution in the deer population. Some of the first findings remain groundbreaking work 30 years later, and still set the pace for deer research nationwide.

Once the research facility was built, biologists collected deer from across the state to stock it. For the first seven bucks collected, five to seven does were isolated in a pen with each buck. These first deer created the genetic foundation for the research that has been conducted during the past 30 years. Today, every deer at the facility traces its lineage to those early penned deer.

Every October, each of the 300 or so deer at the facility is weighed, the bucks’ antler mass measured and blood drawn from selected deer to gather DNA information. The research, funded by the Wildlife Division of the Texas Parks and Wildlife Department through the sale of hunting licenses, seeks answers to the mysteries associated with antler growth. Among the many broad research areas, the WMA’s eight staff members and various university researchers look at which factors contribute to white-tailed deer antler formation and the effects of nutrition on antler formation and body development. Also, the researchers look at the influence of genetics on antler characteristics and if spike-antlered yearlings have the same potential for antler development as forked-antlered deer of the same age.

“These facilities help us isolate genetic, age and nutritional traits that impact antler and body development,” adds Armstrong, as a group of white-tailed bucks run by us, and between protein feeders at the facility. Each of the bucks has a colored tag in its ear that helps researchers identify its age and lineage.

Even though the influence of diet on body weight and antler development might seem common knowledge now, researchers at the Kerr were the first to establish the scientific correlation. By feeding and breeding deer under controlled conditions in the research facilities, investigators can remove any extrinsic environmental factors that may affect the outcome of their studies.

The Kerr research has demonstrated that a deer’s antler size and body condition responds positively to a steady diet of 16 percent protein that’s made up of a pelleted ration of peanut and rice hulls, cottonseed meal and other cultivated ingredients. Conversely, they found if a buck is fed a low-protein diet, the deer will not reach its genetic potential for antler size. Through the regime of rangeland management practices that the WMA endorses, landowners can raise the protein level of their rangeland browse and mimic the results of the Kerr research – thus enhancing the quality of deer on their land.

Perhaps one of the most revolutionary findings researchers at the Kerr uncovered is in a study entitled Spike vs. Fork-Antlered Yearlings 1974-1994. In the study, deer of the same age were fed identical diets, and their genetic phenotypes were carried through subsequent generations by selective breeding. The study revealed that spike-antlered yearling deer will not grow antlers as large as a forked-antlered deer of the same age, even when fed identical diets.

The “once a spike, always a spike” notion that permeates deer camps isn’t technically accurate, although it is pretty close to the absolute truth according to the research conducted at the Kerr WMA. Yearling spikes can grow forked antlers but their overall size is smaller compared to bucks that grow a forked set of antlers at 1 1/2 years of age. The fact that spike deer never get out of their phenotypical rut and become bucks of any significant size impacted in-the-field regulations being pioneered in a six-county region in the Post Oak Savannah east of Austin.

Field Trials

Bob Carroll, TPWD leader for the Oak Prairie Regulatory District, says that in this heavily hunted part of Texas, hunters tend to shoot too many bucks at a young age. The antler restriction regulation is intended to alleviate harvest pressure on the younger bucks. However, hunters prefer to shoot multi-tined bucks and pass on spikes. By passing on the spikes, hunters inadvertently allow them to stay in the herd and breed.

The problem for district leaders was to create a set of regulations that would encourage hunters to pass on young bucks, allowing them to mature, while culling out spikes. At the same time biologists wanted to avoid a moratorium on taking mature bucks or genuine trophy-class deer. Like slot limits on fish, the experimental regulations were designed to limit the number of animals taken in a given age group.

“We looked at the data and it indicated that the TPWD regulations might be inadvertently protecting spike bucks with the one-buck limit,” explains Carroll. “The data collected indicated that hunters were harvesting the first buck they saw that had more than spike antlers. We sent a questionnaire to hunters and landowners prior to the first season of the antler restriction regulations. The results showed that 71 percent of the respondents typically passed up a spike buck to harvest a buck with more points.”

The experimental antler restrictions, which were enforced last season in Austin, Colorado, Fayette, Lavaca, Lee and Washington counties, changed the historic definition from what Texans are accustomed to calling a legal buck. In these six counties a legal buck is defined as having:

  • a hardened antler protruding through the skin, AND:
  • at least one unbranched antler; OR
  • an inside spread measurement between main beams of 13 inches or greater; OR
  • six points or more on one antler.

“The age and antler data collected for the six-county area indicated that 80 percent of the bucks harvested were 1 1/2- and 2 1/2 -year-old deer before we implemented the regulations. We needed to get 3 1/2-year-old and older bucks in the herd and found that the average inside spread of a 3 1/2-year-old buck was 13.2 inches,” says Carroll. “Since a 13-inch inside antler spread was about the same as the distance between the tips of buck’s ears when in the alert position, we felt like this was a good starting point to get more age in the buck herd. The ear-to-ear distance also helps hunters to judge inside antler spread.”

Since implemented this past season, the restrictions reduced the harvest of 1 1/2- and 2 1/2-year-old deer from 80 percent of the animals harvested to 45 percent. Conversely, the harvest of bucks older than 3 1/2 years increased from 20 percent to 55 percent of the six-county harvest total. Carroll says that that progress is significant, as it illustrates how the antler restrictions can limit the harvest of immature bucks and establish a more stable age distribution in the population. He reports that hunters and landowners are supportive.

“Seventy percent of the landowners and hunters surveyed in 2002 supported the antler regulation. Most everything we are hearing from them is very positive. Anecdotal data indicates they are seeing more bucks and older and larger bucks.”

Looking to the Future

According to Carroll, the long-term goal of the antler restrictions is to increase the number of older deer in the six-county buck herd while increasing hunter opportunity in one-buck-limit counties. Ultimately, if proven successful, the regulations will allow hunters in one-buck counties to harvest an additional buck, provided it is a spike.

Carroll explains that “by adding a second buck to the bag limit and mandating that it must be a spike, these regulations allow hunters to harvest the poorest quality bucks in the herd while hunting for an older age buck.” The harvest logic Carroll touts dovetails with the research the Kerr WMA has been conducting for years.

Back in the educational center at the Kerr headquarters, Armstrong continues laying out facts on the genetic and nutritional influences that make one deer grow larger antlers than another. Throughout the center, mounted antlers from various life stages help explain the antler growth of selected bucks. He shows me how one buck, which started out with spike antlers his first year, only grew to be a small eight-point as he matured to 5 1/2 years old. Then he shows another buck that started his second full year of life as a six-point and eventually grew to an impressive size by his fifth year.

“You can’t isolate the genetics of a buck down to one simple gene,” explains Armstrong. “You can equate a buck’s antlers to a house. All kinds of materials go into building a house. Antlers are the same way: a buck’s genetic disposition to phosphorus uptake plays a part in antler growth; his ability to metabolize protein makes a difference; the efficiency at which he digests his food is another factor. There are a million different keys that may unlock a buck’s antler growth potential. What we are doing here at the Kerr will shed light on some of those keys and continue to improve the Texas deer herd.”

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