Deer are a valuable natural resource, but when overpopulated, can cause extensive damage to their environment and ultimately the herd itself. It is estimated there are 35 million deer in the U.S. with over 15% of the population residing in Texas alone1. Within the state, the Edward’s Plateau region, a.k.a. the Texas Hill Country, has one of the densest whitetail populations in the nation, averaging 1 deer to 7 acres, with some counties in the area having an even greater density of 1 deer per 3 acres2. Other areas in the eastern and southeastern U.S. with dense whitetail herds include most of Wisconsin and Mississippi, as well as parts of Michigan, West Virginia, the Carolinas, Louisiana, and Alabama. Population densities in these areas average more than 45 deer per square mile3. In such areas with exceptionally high deer numbers, the implementation of population control measures is imperative to maintain a deer population that is in balance with the environment.
As deer numbers rise in concentrated areas, the ability of the natural resources to meet the increased demand is reduced. In other words, the carrying capacity of the land, or the number of animals the land can support, declines. This issue is exacerbated if there are grazing cattle, sheep, or goats sharing the same tract of land. In addition to animal factors, environmental factors, such as urbanization, drought, fire, and other extreme weather events, can also affect carrying capacity. Environmental factors are often not the same from year to year, meaning the carrying capacity can, and often does, fluctuate seasonally. Whether induced by overgrazing, overpopulation, or mother nature, the outcome is the same – an undersupply of nutrients for growing and adult deer. If these conditions exist for extended periods, deer performance is hindered in more ways than one. Nutritional consequences of a deer population out of sync with its environment can include less desirable antler development, reduced body size and thriftiness, and reduced fawn crop.
Adequate nutrition is necessary for antler development, specifically during spring and summer seasons while antlers are growing. It is estimated while in velvet whitetail antlers grow as much as one and a half inches per week during peak growth! During that time, the buck is mobilizing a lot of nutrients to make this possible, all of which must be replaced by his diet if he is to maintain body condition and bone strength. Thus, insufficient dietary protein, energy, and minerals can result in adult males with decreased antler beam volume. Buck fawns can be equally affected by poor nutrition. If dietary nutrients are limited during initial pedicle development, subsequent antler growth can be negatively affected, even delaying the age at which bucks reach their maximum antler size4.
Antler development isn’t the only aspect of deer performance that suffers from overpopulation. Overall body size is decreased when forage resources are limiting, ultimately reducing thriftiness across bucks, does, and fawns. When nutrient intake declines, body growth is minimized or even reduced. Additionally, less body mass is a sign of fewer nutrient reserves available for mobilization in times of need. Rut, gestation, lactation, and fawn growth are nutrient-demanding processes requiring significant energy expenditures to support increased activity, tissue development, and muscle growth. Deer entering these production phases with limited fuel in the tank, so to speak, will undoubtedly suffer greater nutritional stress than larger deer with ample body reserves.
Similarly, overpopulation conditions that hinder the health or nutritive status of does can lead to poorer fawn crop and increased fawn mortality. Research indicates a 50-60% reduction in fawn crop for does inhabiting nutritionally poor ranges verses those on healthy, productive ranges5. Where forage is abundant, there are sufficient nutrients for nursing does to raise healthy fawns. However, in nutritionally poor ranges, the doe’s energy intake may not meet the requirements for lactation, and milk production suffers. Fawns of these does will likely be weak and more prone to disease and death due to the lack of nutrients from both the doe and their home range. Furthermore, habitats with poor browse and forage quality due to overpopulation will not provide good cover for fawns, increasing the likelihood of newborn fawn predation6. While smaller fawn crops over time may correct the overpopulation problem, it is more humane and ecologically efficient to prevent the deer herd from getting to this point by maintaining the integrity of the native range through proactive population control measures. Not to mention, there can be long-term negative effects of poor nutrition during early development of the surviving fawns as discussed previously.
While there is a better understanding of the nutritional needs of deer today than ever before, many unknowns remain. Variables affecting nutrient requirements include the time of year, stage of production, nutritional characteristics of native browse species, and environmental temperature, among others. Because protein, energy, and mineral requirements will fluctuate with these variables, it is important to routinely observe your herd’s habitat to make effective management decisions. Some tell-tell signs you may be facing an overpopulation issue include noticeable browse lines, limited or nonexistent populations of native forage species preferred by deer, and increased deer sightings.
A critical aspect of managing whitetail numbers is to first understand your deer herd. Camera, spotlight, and infrared surveys can be used to estimate total deer numbers, density, buck-to-doe ratios, and age structures. In addition to census surveys, maintaining harvest records may provide further insight into herd demographics. These suggestions may be most practical for larger landowners or high-fenced ranches but deserve consideration, nonetheless. Wildlife experts with Texas Parks and Wildlife or your local AgriLife extension office should be able to assist with understanding your particular wildlife situation as well as best management practices to achieve your desired goals.
Negative effects of nutritional deficiencies may be seen as many as 2 years after the deficit. Nutritional stress can be particularly detrimental to young fawns and have lasting impacts for generations. Thus, it is imperative to overall herd health and longevity that deer populations be aligned with the carrying capacity of the native range. It should also be noted that supplemental feeding does not resolve nutrient deficiencies associated with overpopulation or overgrazing. Rather, it can further exacerbate the problem since supplemental feeding has been shown to increase fawn crop and survival7. Therefore, it is just as important, if not more so, to implement population management strategies when also providing supplemental feed. Consult with your local wildlife biologist to define your management goals, characterize your deer herd, and identify the population control strategies that will be most effective for your situation.
References Cited
1Wildlife Informer. Deer Population by State (Estimates and Info). Accessed Oct. 2022. Deer Population by State (Estimates and Info) – Wildlife Informer
2Texas Landowners Association. How many deer are in Texas? White-tailed deer populations listed by region. Accessed Oct. 2022. How many deer are in Texas? White-tailed deer populations listed by region – Texas Landowners Association (landassociation.org)
3USDA. Ag Data Commons. White-tailed deer density estimates across the eastern United States, 2008. Accessed Oct. 2022. White-tailed deer density estimates across the eastern United States, 2008 | Ag Data Commons (usda.gov)
4Hewitt, David G., editor. Biology and Management of White-tailed Deer. Taylor & Francis Group, LLC, 2011.
5Armstrong, W. E. and E. L. Young. 2000. White-tailed Deer Management in the Texas Hill Country. Texas Parks and Wildlife Department.
6Buck Manager. Fawning Habitat is Important for Deer Populations. Accessed Oct. 2022. Whitetail Management: Fawns Need Habitat, Too! (buckmanager.com)
7Richardson, C. 2006. Supplemental Feeding of Deer in West Texas. Texas Parks and Wildlife Department. Trans-Pecos Wildlife Management Series, No. 9:1-10.
