One thing I have learned while managing and hunting free-ranging whitetails in South Texas over the last quarter century is the impact rainfall has on antler development. A variety of habitat management techniques can be employed to enhance the habitat such as disking, roller chopping, aerating, burning, even fertilizing, but without deer nutrition rain, these practices are ineffective. The chaparral of South Texas is a harsh environment for deer. To the casual observer, it is simply a desert, but to a trained eye, it is an ecologically diverse ecosystem occupied by a plethora of brush and plant species rich in the valuable components required to support some of the finest deer herds in North America. However, it takes rain in order for the vegetative component to develop and release those nutritional advantages.
To fully understand the importance of rain and its impact on antler size, I tabulated the antler statistics of the six highest-scoring bucks harvested on one Dimmit County ranch. The reason the top six bucks were selected is because only six hunters were allowed to shoot a deer of their choice, hence bucks displaying undesirable antler qualities make up a higher proportion of the harvest, reducing the overall average. By isolating undesirable antlered bucks from the harvest statistics, a unique opportunity to critique those "highly desirable" bucks becomes available. Based on this data, the highest average annual gross scores since 1990 were recorded in 1993 (174 Boone and Crockett average); 1997 (180 Boone and Crockett average); 2000 (171 Boone and Crockett average); and 2001 (172 Boone and Crockett average). It is important to point out that these animals exist on open range, surviving on native forage.
The one thing all these years have in common except for 1997 is that they were preceded by three years of above average rainfall. The year 1997 was preceded by a rather dry year, but 31.04 inches fell throughout 1997, with 48 percent occurring during the spring antler-growing period. Antler mass, the sum of eight circumference measurements, four per antler beam, and how it was affected by rainfall was also analyzed. The highest average mass measurements were recorded in 1992 with 36 inches; and 1993, 1997, and 2000, all of which had average mass measurements of 35 inches. Rain frequency equates to inches of antler.
Droughts of varying degrees have been recorded in South Texas since man has maintained records. The U.S. Weather Bureau defines drought as "a period during which annual rainfall is 75 percent or less of average." From the standpoint of whitetails, however, a drought occurs when vegetation stops developing, and this happens often for various lengths of time throughout any year.
The evaporation rate in South Texas often exceeds annual rainfall. Thus, deer dependent on native vegetation exist with either an abundance or lack of food. In Laredo, for example, the average annual rainfall is approximately 17.9 inches; however, the annual evaporation rate is approximately 114 inches. Thus, it's apparent how harsh this environment can become.Rainfall has a dynamic impact on native vegetation whenever it occurs, but it is not the only ingredient to the production of a healthy deer herd.
In portions of East Texas where rainfall is not a limiting factor, deer quality, particularly antler size, remains below that of South Texas. Some of this can be attributed to genetics, excessive harvest, etc., but the major problem is a lack of plant species diversity. Much of East Texas simply does not have the variety of nutritionally rich plants that occur in South Texas. But by taking advantage of rainfall, East Texas land managers can establish cool and warm season food plots, affording deer an excellent source of nutrition year round. In South Texas, particularly the extreme western portion south of San Antonio, summer food plots are extremely difficult if not impossible to sustain because of the lack of rain and extreme temperatures.
Regardless the amount of rain a particular region receives, additional factors affecting herd quality must be considered. For instance, an overpopulated deer herd can severely damage the habitat by eliminating preferred browse regardless rainfall. Deer numbers must be maintained within the carrying capacity of the land and sex ratios balanced before the benefits from rain can be realized. Domestic stock and its impact on the environment must also be monitored. It is irrelevant how much effort is spent reducing a deer herd if domestic stock numbers are excessive.
Rain "liquid nutrition" is the paramount ingredient for a strong healthy habitat, which equates to quality deer. This is true for fawns as well. With rainfall the South Texas landscape develops a lush understory affording protection for fawns from predators like the coyote.
Sportsmen often blame below average antler quality on lack of rainfall when the real culprit is poor management. Managed lands always have the potential of producing highly desirable-racked bucks. Non-managed lands have little chance of yielding trophy class deer, even under ideal conditions. In my opinion, deer populations in the Southwest should be maintained to thrive under less than ideal range conditions. Thus, when ample rain occurs and range conditions peak, the production of trophy bucks comes closer to reality.