In Missouri, most adult does have twin fawns; triplets are less common. Although the mortality rate for fawns can be 40 to 50 percent, deer have a 95 percent survival rate without hunting once they reach six months of age.
A question often asked by landowners is, "Can I effectively manage deer on my property?" The hunting season framework affords the opportunity for landowners to achieve desirable harvests on any property. Yet landowners' ability to control deer numbers on their property depends upon the land's size, shape and quality of habitat. Habitat quality and hunting pressure on surrounding properties also are important factors to consider.
The amount of land owned by one person decides how much of a role outside factors may play. As described earlier, deer move over large areas. As a result, the ability to manage deer increases proportionally with amount of acres owned. For example, landowners with 10 acres will have less control over deer on their property than landowners with 1,000 acres.
The amount of hunting or other activity on adjacent properties also is an influencing factor. Light or no hunting pressure on surrounding land may make it easier for a person to produce large bucks or increase deer densities. On the other hand, people trying to reduce deer numbers on their property may find it difficult if hunter access is limited on surrounding properties.
The physical shape of the property may affect how often deer move onto adjacent land. A long linear shape, as opposed to a more compact shape, may have more individual deer on the area, but these animals may spend less time there. When surrounded by heavily hunted ground, deer that live on a linear holding would spend more time off the property and, therefore, would be exposed to greater hunting pressure.
Quality of deer habitat and primary sources of food control how much time is spent on an area because deer shift movement patterns according to food distribution. In a year with a good acorn crop, deer may select oak-hickory forests for foraging in the fall instead of agricultural fields. On the other hand, deer may favor agricultural fields at other times of the year and also in years of poor acorn production.
Population Principles
Whether a deer population increases, decreases or remains stable depends upon the balance between reproduction and mortality. Deer reproductive rates in Missouri are high, typical of those throughout much of the lower Midwest. Studies in several parts of Missouri determined deer mortality by monitoring free-ranging deer fitted with radio transmitters. These studies show that fawn mortality during the first six months of life may exceed 40 percent. Predation and farming activities are the primary causes of mortality in fawns less than two months of age.
Without hunting, the annual mortality of six-month-old and older deer is usually less than 5 percent. An exception to this occurs during hemorrhagic disease outbreaks, which take place periodically in Missouri and kill up to 20 percent of the deer in some areas.
Hunting is the leading cause of deer mortality in most of Missouri. Each year hunters take 40 to 70 percent of the antlered bucks and up to 25 percent of the does. It is apparent, therefore, that hunting is the primary factor governing deer abundance. A population model represents how we might expect deer numbers to respond to hunting given the reproductive and mortality rates experienced by animals within the population. The model provides a means of predicting the growth or decline of a population given the number of fawns produced and adults killed each year. Usually the model is not a perfect match. Nevertheless, the population model gives us a reasonable idea of how factors, such as hunting, affect deer populations.
Hunting mortality of does is the most important factor determining whether a population increases, decreases or remains stable. One male can mate with many females, so bucks can remain at much lower numbers than does without affecting reproductive rates. This can be shown by simulating a deer population under various buck and doe harvest rates. Harvests of 10 percent and 40 percent of the antlered deer from a herd has little effect on the overall population growth. Similar harvests of does, however, affect population growth.
If hunting mortality is eliminated, and all other mortality and reproductive factors remain the same, a deer population increases rapidly, nearly quadrupling in size in just 10 years. Growth at this rate, however, could not continue indefinitely. As the deer population increases, it eventually reaches and exceeds the the land's carrying capacity-the number of animals a habitat can support on a sustained basis.
When deer numbers exceed the land's carrying capacity, heavy browsing destroys the habitat. The physical condition of the deer degenerates and results in lower reproductive rates and survival. Ultimately, growth rates and deer numbers stabilize at some lower density (Figure 6). Unfortunately, when deer numbers exceed the lands's carrying capacity, the habitat destruction affects other species, and habitat recovery is slow.
There are many examples of deer populations in various parts of the United States that have grown out of control when hunting was curtailed. Such cases are rare in Missouri but have occurred in localized situations. Knob Noster State Park in west central Missouri provides an example of what can happen when a deer population is not managed.
Deer disappeared from the area around Knob Noster in the early 1900s. Between 1945 and 1947, the Missouri Department of Conservation reintroduced about 50 deer into Knob Noster State Park. The population grew rapidly, and by 1953 most plants showed signs of heavy browsing. A severe winter in 1959-60 caused the only documented case of winter starvation of Missouri deer. Seventeen deer were found dead or starving in Knob Noster, and it is likely there were more. If the habitat had not been browsed severely by too many deer, the deer probably would have survived.
The Missouri State Parks Board, in cooperation with the Missouri Department of Conservation, responded to the situation by conducting a three-day archery hunt in 1960. A total of 1,054 hunters harvested 136 deer. Since this first hunt, periods of hunting have alternated with non-hunting periods. Increasing deer populations and severe browsing characterized nonhunting periods. In recent years, modern firearms hunts have controlled the Knob Noster deer population successfully, and habitat quality has improved.
As illustrated above, uncontrolled populations ultimately exceed the land's carrying capacity. Fortunately, agriculture in much of the Midwest provides an almost unlimited supply of food for deer. Deer in Missouri, especially in the northern agriculture areas, exist at levels well below the land's carrying capacity. These populations could reach much higher densities if deer were not hunted (Figure 6). Severe crop damage and unacceptable numbers of deer/vehicle accidents would take place long before the land's carrying capacity was reached.
The need to control deer numbers in Missouri, therefore, is not related to the land's carrying capacity but to a typically lower cultural carrying capacity-the maximum number of deer that the public will accept before the negative aspects of high deer numbers, such as damage to crops and deer/vehicle accidents, become intolerable.
The Conservation Department's statewide deer management program attempts to maintain deer populations at levels high enough to provide adequate opportunity for hunters and people who enjoy watching deer. Conversely, numbers must be low enough to minimize crop destruction and deer/vehicle accidents. Of course, people do not always agree about how many deer are too many or not enough.
The Conservation Department monitors the attitudes of the two groups most affected by deer abundance: farmers and hunters. Periodic mail surveys serve as the basis for setting deer population goals, along with information supplied by Conservation Department field staff.
Legal hunting most efficiently keeps deer at or below the cultural carrying capacity. Doe harvests have the greatest effect on the population so control of their harvest is necessary to avoid overharvest and to ensure an adequate harvest. Missouri is divided into 59 deer management units (Figure 7). The Conservation Department annually establishes a quota of any-deer permits in each unit that allows the holders to harvest any deer regardless of sex or age. Bonus permits, which restrict harvest to antlerless deer, are issued in units where quotas exceed applications for any-deer permits and increased doe harvests are needed. Until 1997, hunters seeking any-deer and bonus permits had to apply for them, and recipients were chosen by random drawing. Since 1997, any-deer and bonus permits have been sold over the counter through an automated point-of-sale system.
MANAGEMENT UNITS
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Figure 7. Missouri is divided into 59 deer management units. The Conservation Department annually establishes a quota of deer permits in each unit.
odels, public opinion, conservation agent reports, harvest data and deer/vehicle accident summaries are used to set doe harvest goals. Conservation Department wildlife managers know the average harvest success rates on any-deer and bonus permits and the percentage of does in the harvest because this information is gathered annually. Therefore, they can set quotas at levels that will attain the desired doe harvests. Landowners with deer damage problems can recruit hunters with any-deer and bonus permits to achieve a sufficient doe harvest and control the local deer population size.
The quota system has worked well. It provides much hunting opportunity while carefully controlling deer harvests to meet population objectives. Nevertheless, 93 percent of the land in Missouri is privately owned, and hunting access varies among properties. The variability in hunting pressure produces harvests that are high on some properties and low on others. Although the overall unit harvest may be appropriate, there are often spots where hunters have taken too few or too many deer. Fortunately, landowners can control harvests and populations, especially if cooperative agreements are arranged between neighbors.
Figure 9. Population modeling shows the dramatic difference hunting pressure has on the number of antlered deer in an area. The key to management for larger bucks is simply to allow males in younger age classes to survive to older age classes.
Managing Deer: What are the Goals?
Landowners have diverse attitudes toward deer on their property. Some would just as soon have no deer vying for the crops they produce. Others would like to have a deer behind every tree. Most landowners are somewhere in between. Harvest preferences also vary. Some landowners who hunt just want the opportunity to harvest a deer; others want only that trophy buck.
Whether it be population or harvest goals, there are steps that can be taken to increase chances of achieving them. Sometimes a goal may be achieved simply by adjusting harvests. Other times it may require considerable effort, including regulating harvest and cooperating with adjacent landowners.
One difficult question facing most landowners is just how many deer should be taken from a property during hunting seasons. As described above, the answer depends upon many characteristics of the property and those surrounding it. A careful assessment of these conditions is necessary before making even a rough estimate of how many deer to take each year. Even then, this figure will require regular evaluation and correction.
On the previous page, Figure 8 provides some harvest guidelines based on population modeling. The data used to generate these graphs are based on a square mile segment of habitat. Average densities, mortality and reproductive parameters for different regions of the state was used for input. Deer hunting pressure on adjacent properties was entered as light (little or no pressure; bucks are the only deer taken), moderate (heavily hunted the first weekend of the firearms season; little hunting after that; both bucks and does taken but mostly bucks), or heavy (hunting pressure heavy throughout the firearms season; both bucks and does harvested at high rates).
The initial deer densities are based on regional averages. These, of course, vary locally and are greatly influenced by historical hunting pressure on and off the area. Therefore, actual starting values on your area may be different from those used in these calculations. The recommended harvests indicate the number of deer that can be removed and still maintain a stable population. If higher or lower deer densities are desired, harvests should be adjusted.
Although the recommended harvest figures can be used as a guide to deer management on your lands, monitoring deer populations is important. Annual population estimates are essential to decide if goals are being achieved. It is likely that adjustments in annual harvests will have to be made. This requires continual monitoring to re-evaluate harvest strategies. In the end, landowners need to design a harvest schedule that works best for them.
Click on the region for graphs of harvest guidelines or chose from the menu below.
Figure 8. The data used to generate these graphs are based on a square mile segment of habitat. Average densities, mortality and reproductive parameters for different regions of the state are used for input. Deer hunting pressure on adjacent properties was entered as light (little or no pressure; bucks are the only deer taken), moderate (heavily hunted the first weekend of the firearms season; little hunting after that; both bucks and does taken but mostly bucks), or heavy (hunting pressure heavy throughout the firearms season; both bucks and does harvested at high rates).
The initial deer densities are based on regional averages. These, of course, vary locally and are greatly influenced by historical hunting pressure on and off the area. Therefore, actual starting values on your area may be different from those used in these calculations. The recommended harvests indicate the number of deer that can be removed and still maintain a stable population. If higher or lower deer densities are desired, harvests should be adjusted.
Specialized Deer Management
Considerable interest in managing land for mature bucks has developed in recent years. Two tenets dominate popular and management-oriented literature: quality and trophy management. The concept of quality deer management began in the southern United States. Its primary objective is to manage deer populations and habitat to ensure a quality hunting experience. Although deer in older age classes is one goal, other factors are considered.
Trophy management is more restrictive. Its primary emphasis is producing a buck with the largest possible rack. This requires intense management and strict control over harvests. It is not practical in most situations in Missouri. Most trophy management is confined to large land ownerships in the southern United States. Information presented in the discussion of population management is based on regional averages that promote the regulation of deer numbers only. Antlered buck harvest is not regulated regionally because buck harvest has little influence on total population levels. Under this management scheme, few bucks survive to older age classes.
A common concern expressed by deer hunters is a lack of bucks with well-developed antlers. Often the hunters believe that the deer lack adequate nutrition or are inbred. The real problem, however, is that most of the bucks they see are 1 1/2 years of age. In some areas, bucks simply do not live beyond their first set of antlers because of heavy hunting pressure. Although genetic and nutritional factors can affect antler size, the majority of deer in Missouri that reach 3 1/2 to 4 1/2 years of age are trophies to most hunters. The key to management for larger bucks is simply to allow males in younger age classes to survive to older age classes.
Managers can accomplish this by not shooting young bucks during the hunting seasons. This may seem too simplistic, but deer survival is high when they are not hunted. Chances are good that a buck will survive if not taken during the hunting season and, in so doing, will grow bigger antlers the following year.
Modeling hypothetical populations in which buck harvest is varied illustrates this the best. Sex and age ratios differ considerably depending upon the percentage of bucks harvested. A model with 10 percent antlered buck harvest indicates that 50 percent of the antlered bucks are between 2 1/2 and 4 1/2 years old, and 24 percent are 4 1/2 years old and older.
In contrast, populations where bucks are highly exploited, only 27 percent of the antlered bucks are between 2 1/2 and 4 1/2 years old and 1 percent are 4 1/2 years old and older. Antlered bucks would make up 35 percent of the total population in the low buck-exploited population compared with 16 percent in the high buck-exploited population (Figure 9).
When regulating buck harvest, the same factors that affect populations on a property apply except that bucks are more active and have larger home ranges. This is especially true during the breeding season, which coincides with the firearms season. As a result, the minimum acreage required to effectively manage quality bucks is higher. Unless ownership is at least 1,000 acres, effective management of bucks in older age classes will require the cooperation of surrounding landowners.
Landowners desiring this type of management should contact neighbors with similar goals and develop a plan that protects 1 1/2- and 2 1/2-year-old bucks during the deer hunting seasons. The relative experience of deer hunters involved dictates minimum antler size requirements. If most deer hunters are experienced hunters, a minimum antler spread, such as length beyond the ears, may be established.
Another way to restrict harvest to bucks with a minimum number of points. However, the number of points and deer age do not always correlate. Hunters may take yearlings with many points that should be protected. In contrast, hunters may pass up some older, larger deer with well-developed antlers but too few points to qualify for harvest.
Controversy currently exists over whether spike bucks should be culled. In Missouri though, most bucks that reach 4 1/2 years of age will be trophies to most hunters. Given most hunter expectations and the inability to control harvests and dispersals on small land holdings in Missouri, the best strategy is to pass up these young bucks during the hunting seasons. The result usually will be the production of a quality animal several years down the road.
Yearling bucks should be protected if your goal is to produce adult animals with large racks. Because mortality is low when they are not hunted, young bucks are likely to survive if not taken during the hunting season and will grow larger antlers the following year.
Record Keeping
Assessing the success of a deer management program on a property is an important part of every management effort. This can be as simple as keeping track of the number of deer observed and taken during the deer hunting seasons each year to more scientific efforts, such as aerial census of deer. Most landowners prefer the former, but those whose primary goal for their land is deer management may choose a more careful evaluation method.
Simple records carefully collected over a period of years can tell a lot about the status of the deer population. Most often landowners take these records during the deer hunting seasons when they spend the most time in the woods. Diaries of hunting trips (see Appendix) not only can be rewarding historical accounts of hunts and observations but also can provide useful information about the deer population. Population indices, such as the number of deer sighted by sex and age per hour, may be determined from this type of information.
Deer sightings per hour are used by some state conservation agencies as a population measurement on public lands. Many biologists believe deer sighting indices are better able to track population changes than track or spotlight counts. Population indices become more meaningful over time and are not intended to produce complete counts; they show general trends in sex and age ratios and population changes. The key is to record this information consistently from year to year.
Annual records of harvested deer, their sex, age, weight, antler beam circumference and date taken also may be useful (see Appendix). Records may provide information on the herd structure and condition that can be used to gauge the success of a management effort.
Census, or an actual count of deer, is much more expensive than those methods listed above and will not be a practical option for most landowners. An aerial census with a helicopter over snow-covered ground currently is the most accurate way to count deer. Unfortunately, necessary conditions, such as adequate snowcover, do not consistently occur in Missouri.
Infrared scanners, which detect body heat and do not require snow cover, have shown some promise for counting deer. Other methods include fecal pellet group counts, spotlight surveys and track surveys. These methods are of questionable accuracy if actual deer population estimates are required. They may be of more value as an index to population trends than for counting deer.
