DEERDeer are probably the most widely distributed and best-recognized large mammals in North America. The white-tailed deer (Odocoileus virginianus) is found throughout much of North America. The mule deer (O. hemionus) is primarily a western species restricted to buttes, draws, and stream bottoms with sufficient forage. The black-tailed deer (O.h. columbianus) is a subspecies of the mule deer. Both white-tailed and mule deer are very important game animals. In 1974 about 2 million white-tailed deer were harvested by over 8 million hunters. The trend in both harvest and hunter numbers has been generally upward since then. The positive economic value of deer through license fees, meat, and hunter expenditures for equipment, food, and transportation can be measured in hundreds of millions of dollars. It is estimated the value of each deer harvested in the United States to be $1,250. With the additional aesthetic value of deer to landowners and vacationers, importance of deer as a wildlife resource cannot be disputed.
Despite their economic and aesthetic values, deer also have a variety of negative economic impacts—they damage crops and personal property, and harbor diseases common to humans and livestock. Unlike moles, rats, and other species implicated in damage, deer cannot be casually eliminated when in conflict with humans. But neither can landowners be expected to bear the entire burden of support for this valuable public resource.
These factors often make deer damage control a difficult social and political problem as well as a biological and logistical one. Control methods are built around effective deer herd management. Thus the various state wildlife agencies are often indirectly or directly involved through subsidy of control techniques, direct damage compensation payments, or technical advice.
Scare devices, repellents, and shooting all have a place in deer damage control. Effective control for fields, orchards, and other large areas, however, usually depends on excluding the deer with one of several types of fences, discussed later in this chapter. Toxicants, fumigants, and in most cases, trapping, are not used in deer control.
The volume of literature on deer ecology and management exceeds that for any other wildlife species. The following review is meant as a brief summary using the white-tailed deer as an example (the mule deer is very similar in all respects).
Identification
Deer are even-toed ungulates of the family Cervidae. Adult animals may weigh 50 to 400 pounds (23 to 180 kg) depending on species and location. Their general form is well-known. At birth, fawns are rust-colored with white spots. Their spotted coats are shed in 3 to 4 months and are replaced by a grayish-brown fall and winter coat. The summer coat of adult animals is reddish-brown. Underparts of the tail, belly, chin, and throat are white during all seasons. Antlers grow on males (bucks) from April to August. Antler development is nourished by a layer of soft, vascularized “velvet” on the antlers. The dried velvet layer is rubbed off and the antlers polished during the fall rut (breeding season). Antler size depends on nutrition, age, and genetics. Mule deer antlers are forked while the tines of a white-tailed deer’s antlers arise from a central beam. Both mule deer and white-tails have deciduous antlers that are shed in mid-winter. The rump and tail area and facial features also differ slightly between the species. Both mule and white-tailed deer lack upper incisors.
Habitat
Deer are creatures of the forest edge rather than the dense, old-growth forest. They thrive in agricultural areas interspersed with woodlots and riparian habitat. They favor early successional stages which keep brush and sapling browse within reach. Dense cover is used for winter shelter and protection.
Food Habits
Browse (leaves, stems, and buds of woody plants) is generally available all year and is a staple food for deer. Plant species vary considerably in quality and regional availability, so a list is not presented here. Forbs are eaten in spring and summer when available. Fruits and nuts (especially acorns) are seasonally very important. Grasses are relatively unimportant. Agricultural crops--corn, soybeans, small grains, alfalfa, vegetables, and fruit trees--are readily eaten when available. Local food habits studies are available in most states--consult your local wildlife agency.
Nutrient requirements and the amount of food consumed vary with age of the animal, season, and the reproductive cycle. Daily dry matter consumption averages 2% to 4% of live body weight. For adult bucks, daily consumption is greatest in spring and averages 4.4 to 6.4 pounds (2.0 to 2.9 kg) of air-dry food per day. Consumption is about half that during winter. For does, greatest daily food consumption occurs in early fall, just prior to the breeding season.
General Biology, Reproduction, and Behavior
Breeding occurs from October to January depending on latitude. Peak activity is in November. Does are in heat for 24 hours every 28 days for 2 to 3 consecutive cycles. One buck may inseminate several does. No pairing takes place. Most does breed during their second fall, although on good range up to 30% of the doe fawns (6 months old) will be bred. Gestation is about 202 days. The peak of fawn drop is in May or June. Most reproducing fawns give birth to a single fawn, but adult does typically bear twin fawns. Reproductive potential is very sensitive to nutrition. Fawns weigh 7 to 8 pounds (3.2 to 3.6 kg) at birth and increase in weight for 5 1/2 to 6 1/2 years. Adult size varies with latitude. In northern states, a mature buck may weigh 200 to 300 pounds (90 to 135 kg). A key deer buck (white-tailed deer subspecies) in Florida may weigh only 50 pounds (22.5 kg). Does average 25% to 40% less than bucks for all subspecies.
Deer are most active in early morning and evening. They have a home range of several hundred acres (ha), but this varies with season, sex, and habitat quality. In northern areas, deer gather (“yard”) in dense cover for the winter. They may move long distances from summer range to a winter yard. Life expectancy is dependent on hunting pressure and regulations. Records show whitetails living 20 years, although 10 to 12 years is noteworthy in the wild.
Damage and Damage Identification
Deer damage a wide variety of row crops, forage crops, vegetables, fruit trees, nursery stock, and ornamentals, as well as stacked hay. In addition to the immediate loss of the crop being damaged, there is often residual damage in the form of future yield reduction of fruit trees or forage crops such as alfalfa. Ornamental trees or nursery stock may be permanently disfigured by deer browsing. Under high densities deer may severely impact native plant communities and impair regeneration of some forest tree species. Besides vegetative damage, deer/ vehicle collisions pose a serious risk to motorists, and deer have been implicated in the distribution and transmission of Lyme disease.
Damage identification is not difficult. Because both mule deer and white-tailed deer lack upper incisors, deer often leave a jagged or torn surface on twigs or stems that they browse. Rabbits and rodents, however, leave a clean-cut surface. In addition, deer tracks are very distinctive. The height of damage from the ground (up to 6 feet [1.8 m]) often rules out any mammal other than deer. Deer often are observed “in the act” of causing damage.
Economics of Damage and Control
A national survey conducted by USDA’s National Agricultural Statistics Service in 1992 identified deer damage as the most widespread form of wildlife damage. Forty percent of the farmers reporting had experienced deer damage. No estimate exists of nationwide annual crop losses to deer, but damage estimates have been made for some states. In Wisconsin, a 1984 survey of farmers suggested minimum statewide deer damage of $36.7 million annually. A similar study in Pennsylvania estimated the annual crop loss at $16 to $30 million. The situation is similar in most agricultural states with moderate to high deer densities. Estimates suggest that the cost of deer-vehicle collisions may exceed $100 million each year in the United States and Canada. In fact, the cost of deer/ vehicle collisions was estimated at $100 million in Wisconsin alone in 1990.
Deer also damage nurseries, landscape plantings, and timber regeneration. However, as established earlier, deer are a valuable public resource. Cost estimates for control techniques were presented with the appropriate techniques. A cost/benefit analysis is always advisable before initiating a control program.
Two additional economic aspects are worth consideration. One involves farmer tolerance for deer damage. Two summaries of social science research related to deer damage demonstrated that a majority of farmers were willing to tolerate several hundred dollars in deer damage in exchange for the various benefits of having deer on their land. Thus “total damage” figures are misleading because only a small percentage of the farmers statewide or nationwide are suffering sufficient damage to warrant control or compensation.
The second economic consideration involves state-funded programs of subsidies for damage control materials or direct compensation for crop losses. Such programs can be very costly but are probably necessary where large deer herds are maintained in agricultural landscapes. As an example, the Wisconsin Wildlife Damage Program expended $2.25 million in 1992 for abatement materials, claims, and administration. The program is a collaborative effort of the Wisconsin Department of Natural Resources, USDA-APHIS-ADC, and Wisconsin counties and is very effective. Individual states vary greatly, however, in their degree of financial or technical assistance. Consult your state wildlife agency for information on compensation or cost-sharing programs. Also, many states have local publications on deer and deer damage--Pennsylvania, Wisconsin, Minnesota, Michigan, and New York, for example. Consult your local Extension office or state wildlife agency.
Legal Status
Deer are protected year-round in all states and provinces, with the exception of legal harvest during appropriate big-game hunting seasons. In cases of severe or persistent damage, some states may issue farmers special permits to shoot deer at times other than the legal hunting seasons. Regulations vary on the necessary permits and on the disposal of dead animals. The popularity of deer as game animals and the need to curb poaching have led to the development of severe penalties for illegal possession. No lethal deer control can be initiated before consulting your local state wildlife agency. By law, some states provide technical assistance or direct compensation for deer damage. This is discussed under the section on the Economics of Damage and Control.
Damage Prevention and Control Methods
Exclusion
Fences provide the most consistent control: 8-foot (1.4-m) woven wire fence, Tensar®, or wooden snow fence around small plots or haystacks. Several configurations of electric fences are available: vertical five, seven, or nine-wire, slanted seven-wire, single strand, and others. Individual tree protectors include: woven wire or plastic cylinders.
Cultural Methods and Habitat Modification
Plant trees and shrubs that are resistant or less susceptible to deer damage.
Harvest crops as early as possible to reduce vulnerability.
Lure crops may divert deer away from areas that are susceptible to damage.
Habitat modification generally is not recommended.
Frightening
Gas exploders, pyrotechnics, gunfire, or tethered dogs provide temporary relief.
Repellents
A wide variety of commercial formulations is available: area repellents--applied near plants to be protected, repel by smell; contact repellents--applied directly to plants to be protected, repel by taste; a few, such as Deer-Away®, possess characteristics of both groups.
Toxicants
None are registered.
Live Capture
Deer can be live-trapped or chemically immobilized for removal by professional biologists--useful only in special cases, such as city parks.
Shooting
Sport hunting can reduce deer populations and should be encouraged. Some states may issue permits to shoot deer outside normal sport hunting seasons.
ACKNOWLEDGEMENTS
The above information was adapted from PREVENTION AND CONTROL OF WILDLIFE DAMAGE with permission of the editors, Scott E. Hygnstrom, Robert M. Timm, and Gary E. Larson (Cooperative Extension Division, Institute of Agriculture and Natural Resources University of Nebraska-Lincoln, United States Department of Agriculture Animal and Plant Health Inspection Service, Animal Damage Control, Great Plains Agricultural Council Wildlife Committee).
