Can QDM Improve Deer Management in Forested Landscapes? - Paul D. Curtis
Department of Natural Resources, Cornell University. Ithaca, NY 14853
There is little doubt that deer (Odocoileus virginianus) management is demanding increased attention and resources from many state wildlife agencies. Deer conflicts have greatly increased during the past 10-15 years (Flyger et al. 1983, Diamond 1992). Population increases of deer in parks and suburbia have been aided by hunting restrictions imposed by towns and private landowners (Curtis and Richmond 1992). Hunting is the traditional control method used to manage deer numbers in rural landscapes. However, long-term declines in hunter participation, and limited hunter access to private and public lands, may soon make it difficult to harvest adequate numbers of deer.
The challenge now facing many wildlife agencies is how to manage growing deer herds to meet a variety of conflicting public demands. Deer present safety hazards to motorists, consume ornamental shrubs, and are perceived as agents in Lyme disease transmission (Connelly et al. 1987, Decker 1987, Siemer et al. 1992). These negative deer-people interactions have increased public concern and awareness about deer management, and expanded the list of potential stakeholders in the decision-making process.
Deer also have substantial positive recreational and economic values. During the late 1980s and early 1990s, nearly 200,000 deer were harvested in New York, and another 400,000 deer were killed in Pennsylvania during hunting seasons each year. Kosack (1991) estimated that income generated by deer hunting adds more than a billion dollars to the Pennsylvania economy annually. The last three generations of hunters have come to expect high deer densities and associated harvests as normal and sustainable (deCalesta 1997), and hunters represent a significant lobbying force for maintaining current or expanded deer population levels.
Increasingly, wildlife management agencies are being asked to balance the positive and negative values of deer, and develop management strategies that are acceptable to many stakeholder groups. It's impossible to remove politics from the decision-making process, and no matter what the final outcome may be, not everyone will be supportive of a single solution. However, Quality Deer Management (QDM) offers a flexible approach that could potentially regulate deer numbers across broad agricultural and forested landscapes, yet still be acceptable to many stakeholder groups.
Deer as a Keystone Herbivore
Chronic high densities of deer may have multiple and often substantial negative impacts in forest communities (Waller and Alverson 1997). Paine (1969) defines a keystone species as one that affects the abundance of other species, and community structure by changing the relative numbers of competing species. It is very clear that deer influence the relative abundance of tree seedlings and shrubs in forest stands. Forestry textbooks mention that deer browsing can be a problem for regenerating economically-valuable trees, such as oaks. Suppression or elimination of the most-favored seedlings results in a slow but steady conversion of the forest to less palatable species, such as American beech. At very high densities, grasses and ferns may dominate vegetation within the reach of deer. Ferns can interfere with the germination and growth of desirable trees, and thereby add to the direct impacts of deer feeding. Slow-growing conifers like eastern hemlock may be particularly sensitive to deer damage.
Deer also eat many species of native herbs reducing plant diversity in the forest (Waller and Alverson 1997). Rare lilies and orchids can be adversely impacted by deer feeding, and fencing may be required to sustain populations of these flowers. The height of trillium can be used as an indicator of deer browsing pressure and density (Anderson 1994). In northwestern Pennsylvania, hemlock stands lost 60-80% of their ground-cover species during the last 70 years as a direct impact of deer browsing.
Bird populations have also been severely reduced by deer over-browsing. Canopy-nesting birds declined 37% in abundance and 27% in species diversity at high deer densities (deCalesta 1994). Forest structure is modified by deer, and bird species that nest in low shrubs are particularly sensitive to deer damage. Biodiversity can be diminished across entire ecoregions.
Finally, deer quality is diminished when inadequate food resources are available, and the potential exists for dramatic herd reductions during severe winters. Pennsylvania deer herds have experienced steady growth during the past 80 years, except during the late 1930s and 1970s, when a series of severe winters cut herd size nearly in half (deCalesta 1997). Deer populations maintained at lower densities in balance with their food resources are less likely to be impacted by deep snow and cold temperatures. As more forage is available per animal, deer will have greater fat reserves to make it through difficult winters, and bucks may produce better-quality antlers. This is the biological basis for QDM.
Scale-Related Deer Management
Small-scale options- Many things can be done to protect vegetation and tree seedlings from deer if only a few acres require protection. Tree-tubes can be used to protect seedlings and get the terminal bud above the reach of hungry deer. Simple electric fences baited with attractants or repellents can protect small areas if deer densities and foraging pressure are low. Landowners have significantly reduced deer damage to orchards and Christmas tree plantations on blocks up to 20 acres in size using invisible fencing and dogs with radio-collars.
All of these strategies have significant installation costs, and are primarily useful with high-value crops that produce an annual income (e.g., orchards). The economic return for enhanced forest regeneration has not been well-documented. Also, these methods perform best in areas with low to moderate deer feeding pressure, a criteria that has already been exceeded in many agricultural and forested landscapes. Consequently, other management strategies are needed to cost-effectively control deer impacts across broad landscapes.
Large-scale options- Few low-cost options are available to enhance forest regeneration on areas hundreds or thousands of acres in size. Larger-scale timber harvests have sometimes succeeded in "saturating" local deer herds with more new browse than they can consume. Although this strategy can work to regenerate some hardwood species, seedlings that are highly preferred by deer may be selectively removed, even at relatively low deer densities. At 20 deer/square mile, seedlings of six tree species were missing or prevented from reaching the overstory by deer browsing (deCalesta 1992). As deer densities exceeded 20 deer/square mile, clear-cut sites became monocultures of black cherry, and uncut sites were dominated by American beech and striped maple (Tilghman 1989). Obviously, timber harvests can only produce adequate diversity in tree species during regeneration cuts in areas where deer numbers are maintained at low to moderate densities. QDM has the potential to reduce deer numbers over large areas (thousands of acres), and improve biodiversity in our future forests. QDM also makes sense economically, because it primarily requires a change in hunter and landowner attitudes to implement.
Quality Deer Management Applications
The main goals of QDM are to shift the age and sex structure of the deer population, and provide more forage per deer so each animal is in better physical condition (Miller and Marchington 1995). The benefits to hunters that make this strategy attractive include: (1) a higher proportion of bucks in the deer herd, (2) more mature bucks that are likely to have larger racks, (3) an increased opportunity to harvest deer as more does are removed from the population, and (4) a stable deer population that is in better physical condition and less likely to succumb to severe winter weather. Also this program will require increased hunter skill to identify and select appropriate deer to harvest, and many sportsmen find that this increases the quality of the hunting experience. Drawbacks for some hunters are that deer will be less visible at lower densities, and more female deer must be harvested. In addition, as an area is recognized to have large bucks, poaching and trespass problems may need attention. Accomplishment of these changes in deer management will require cooperation of hunters and landowners, and a shifts from traditional bucks-only deer seasons.
The basics guidelines for QDM are readily available (Miller and Marchington 1995), so I will only highlight a few of the most important components here. First, is enough land area available to effectively implement QDM? Although QDM can be practiced on 500 acres, it is better to have at least 1,500 acres in this management system to control boundary affects and allow for deer movement. It may be possible to get neighboring landowners to form a cooperative to ensure that adequate land area is available to measure changes in deer quality.
Second, does the habitat provide adequate food to maintain healthy deer? In mixed agricultural and forest land, crops provide sufficient resources for deer. However, large blocks of mature forest where there has been little timber harvest may not provide adequate browse to get deer through a tough winter. Either cuttings or plantings may be necessary to provide food for deer. Lure crops (i.e., alfalfa, corn) may be a way to concentrate deer feeding in areas away from sensitive forest regeneration.
Third, are hunting rules and regulations flexible enough to allow adequate harvests of antlerless deer? Many state wildlife agencies will work with landowners or hunt clubs to help them achieve their deer management goals. To reduce deer densities across broad landscapes and provide more food for bucks will require aggressive harvests of antlerless deer through a permit or quota system. Often equal or greater harvests of does than bucks are required for several years to help balance the deer sex ratio. Over time (4 to 5 years), the proportion of bucks and associated buck harvest from the herd will slowly increase.
Fourth, can adequate hunter cooperation be achieved? A primary objective of QDM is to protect yearling and 2.5-year-old bucks so they become more mature and have time to grow large antlers that hunters desire. On good range, 3.5- or 4.5-year-old bucks can produce quality antlers that will provide hunters with trophy opportunities. It requires very ethical and committed hunters to make this investment in the future. QDM programs are doomed to failure unless there is sufficient buy-in and self-policing among cooperating hunters.
Fifth, although not absolutely required, careful record-keeping is a great way to measure progress over time. Recording the number of points, antler-beam diameters, and dressed weights of bucks harvested can provide valuable data to determine if a QDM program is working as it should. The total number of deer removed from an area by sex and age is also important. QDM cooperatives that have the best success rates and hunter satisfaction are those that maintain harvest records to fully document their impacts.
QDM requires changes in hunter behavior and cooperation with landowners to meet management goals. Sportsmen benefit by having the opportunity to take the trophy buck of a lifetime and experience a quality hunt. Landowners benefit by selecting more ethical and experienced hunters, lowering deer densities on their property, and ultimately reducing deer impacts to crops and forests. We all benefit from more healthy forests with a diversity of native bird, mammal, and plant species.
Anderson, R. C. 1994. Height of white-flowered trillium (Trillium grandiflorum) as an index of deer browsing intensity. Ecol. Appl. 4:104-109.
Connelly, N. A., D. J. Decker, and S. Wear. 1987. Public tolerance of deer in a suburban environment. Proc. East. Wildl. Damage Control Conf. 3:207-218.
Curtis, P. D., and M. E. Richmond. 1992. Future challenges of suburban white-tailed deer management. Trans. N. Amer. Wildl. Nat. Resour. Conf. 57:104-114.
deCalesta, D. S. 1992. Impact of deer on species diversity of Allegheny hardwood stands. Proc. Northeast. Weed Sci. Soc. Abstracts 46:135.
deCalesta, D. S. 1994. Effects of white-tailed deer on songbirds within managed forests in Pennsylvania. J. Wildl. Manage. 58:711-717.
deCalesta, D. S. 1997. Deer and ecosystem management. Pages 267-279 in W. J. McShea, H. B. Underwood, and J. H. Rappole, eds. The science of overabundance: deer ecology and population management. Smithsonian Inst. Press, Washington, D.C.
Decker, D. J. 1987. Management of suburban deer: an emerging controversy. Proc. East. Wildl. Damage Control Conf. 3:344-345.
Diamond, J. 1992. Must we shoot deer to save nature? Nat. History 8(Aug.):2-8.
Flyger, V., D. L. Leedy, and T. M. Franklin. 1983. Wildlife damage control in eastern cities and suburbs. Proc. East. Wildl. Damage Control Conf. 1:27-32.
Kosack, J. 1991. Hunting is a booming business. Penn. Game News 62:14-19.
Miller, K. V., and R. L. Marchington. 1995. Quality whitetails: the why and how of quality deer management. Stackpole Books, Mechanicsburg, Penn.
Siemer, W. F., B. A. Knuth, D. J. Decker, and V. L. Alden. 1992. Human perceptions and behaviors associated with Lyme disease: implications for land and wildlife management. HDRU Series 92-8, Human Dimensions Res. Unit, Dep. Nat. Resour., N.Y. State Coll. Agric. and Life Sci., Cornell Univ., Ithaca, N.Y. 100 pp.
Tilghman, N. G. 1989. Impacts of white-tailed deer on forest regeneration in northwestern Pennsylvania. J. Wildl. Manage. 53:524-532.
Waller, D. M., and W. S. Alverson. 1997. The white-tailed deer: a keystone herbivore. Wildl. Soc. Bull. 25:217-226.
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