image

Photograph by Joe Mac Hudspeth, Jr. · www.southernfocus.com

Magazine


The Need for Doe Harvest in Mississippi

From the Winter 2008 issue

By Bronson Strickland and Steve Demarais, Mississippi State University
Lann Wilf, Mississippi Department of Wildlife, Fisheries and Parks

The quote “All good things must come to an end…,” applies to many situations in life, like your favorite team’s winning record and your summer vacation. Another application of this quote is with deer population management. The capacity to grow and expand was critical for recovery of deer populations during the restocking efforts of 30 to 50 years ago. A few deer relocated to a new area and protected from hunting were able to rebound and saturate the forests. Unfortunately, all good things must come to an end. Now, in many areas there’s an overabundance of deer.

The tremendous capacity for deer population growth was first documented in the 1930s. A research population was established within a deer enclosure with 4 adult females and 2 adult males. Within 5 years, this population had grown to an amazing total of 133 deer. At this growth rate, the population was more than doubling itself every other year. Using this same growth rate, a doe and buck could multiply to 25 deer in 5 years, 300 deer in 10 years, and an astounding 45,000 deer in 20 years (Figure 1)! Obviously, this growth rate could not be maintained due to a limitation of physical resources, including food and space. By monitoring the deer population for many years, the researchers observed what is now termed density-dependent population growth. That is, the population growth rate declines as population size or density increases beyond optimum conditions.

image
Figure 1.

As deer populations grow, increased foraging pressure reduces the quantity and quality of forage resources over time. Habitat quality declines, which is followed by a decline in health of the deer. Decreased herd health is evidenced by decreased fawning rates and body weight and higher mortality of fawns and older deer. These effects were documented in one population that was protected from hunting and allowed to grow to the absolute limits of the habitat. Deer were so small that many people suspected the population was somehow genetically different than surrounding deer herds. Wildlife managers were eventually given permission to allow regulated hunting and the subsequent changes in deer quality were remarkable. After 5 years of significant harvest, biologists documented a 96% and 75% increase in body weight of yearling and 2-year-old bucks, respectively. Also, antler beam diameter increased 93% and 35% for yearling and 2-year-old bucks, respectively. Genetics were not the problem with this deer herd, food limitation due to extreme deer numbers was the problem.

Harvest is Necessary

Clearly, deer must be harvested to keep their populations under control. But how many deer should we harvest? Well, that depends on several factors. First, you must determine what your objectives are – do you want many low-quality deer, or do you want fewer high-quality deer (unfortunately, you can’t have both). Second, inherent habitat quality affects how many deer the habitat can support. In lower-quality habitats deer numbers must remain lower to achieve high-quality animals (in terms of antler and body size). Lastly, it depends on how many fawns are killed by predators, a relatively new problem in the southeastern U.S. We’ll now expand on each of these factors.

Mississippi State University and the Department of Wildlife, Fisheries and Parks have demonstrated how deer density influences animal quality, and one of the best examples is from the Mississippi Delta. Implementing a heavy doe harvest caused yearling buck body weights to increase 33% and yearling buck main beam lengths increased over 200%! Antler and body growth were limited due to a shortage in food supply caused by an overabundance of deer. Simply decreasing the deer herd through regulated hunting allowed the natural vegetation to respond and animal quality responded soon thereafter.

Believe it or not, up to 30% of the does can be harvested annually in most Mississippi populations. This harvest rate will typically keep the population below the carrying capacity of the habitat and improve deer quality. By improving deer condition you will actually increase reproductive effort, which ensures that in most situations you can’t overharvest a deer herd to the extent of eliminating it. Density-dependent population regulation works in both directions. As the population increases, reproductive success and survival decreases. As a deer population is reduced through harvest, their reproductive success and survival increase. The implications of this relationship can cause frustration for landowners and hunters. Initial harvest reduces deer density, but increased health actually increases the growth rate, and thus the need for additional harvest. Thus, an adequate antlerless deer harvest is not a short-term solution, but must be part of a long-term management program.

How Many is Too Many?

So how do you determine how many to harvest? As a general rule, in lower-quality soil regions a harvest of 1 doe per 100 acres may be appropriate. In higher-quality soil regions, like the Delta, a harvest of up to 1 doe per 25 acres may be suitable. Determining habitat quality and specific harvest numbers is best left for a wildlife biologist familiar with your property. If you don’t have the help of a biologist, start with a lower harvest rate and increase the harvest rate annually until you reach the desired balance of deer population size and deer quality.

We are often asked “which doe should I harvest?” Should we target the really young does, or should we strive to harvest the really old does? If you restrict your harvest only to a particular age you may fall short of your annual goal. Our philosophy is to harvest any female deer when you have the opportunity, but avoid the harvest of buck fawns. One safer approach to avoiding buck fawns is to avoid all fawns, but careful hunters can discriminate male and female fawns based on the presence of antler buds in the males. The bottom line is to harvest an adequate number of female deer, so don’t worry about which type of female.

What about coyotes, are they impacting deer populations? High coyote populations can certainly impact fawn production. Occasionally, coyotes will kill adult deer, but not enough to affect the population. A biologist can help you identify if you have a fawn predation problem. If you do, your first action should address management of the habitat for proper fawn cover. Thinning forest stands, prescribed burning, and conversion of old fields to a permanent cover with native grasses are all good solutions. Trapping coyotes may be the least effective and most expensive option. So please check with a biologist to help you develop the best management plan for your property.

Sex Ratios

If there is heavy buck harvest and inadequate doe harvest the sex ratio can become unbalanced and affect the peak of breeding activity in a deer population. Skewed sex ratios during the breeding season can result in does being bred until their second estrus period. A prolonged breeding season takes a toll on bucks because they have to expend more energy later into the winter, instead of eating and recovering from the “rut.” A later breeding season delays birth date, which means fawns will be smaller than normal during their first winter. The breeding season varies throughout Mississippi due to a combination genetics, deer herd composition (herd sex ratio and age structure), and habitat quality. Figure 2 shows general trends in the breeding season by county. The breeding season in your particular area may be somewhat different, depending on local deer herd conditions.

The only thing that’s constant in life is change. Despite the fact a buck-only harvest was the proper management prescription years ago, now we face a new challenge – keeping deer populations under control. The most influential management activity you can do is harvesting a sufficient number of female deer to keep the population below carrying capacity. This activity alone will improve deer body size, antler size, and reproduction. Remember, all good things must come to an end.