How Deer and Beaver Affect You and Your Land and What You Can Do About It - Kristi Sullivan.
Kristi Sullivan and Paul Curtis, Department of Natural Resources, Cornell University, Ithaca, NY 14853. (607) 255 - 5508
Viewing wildlife on your land can be a very rewarding experience. However, some species can become overabundant and may cause damage or economic losses. White-tailed deer and beaver numbers have increased dramatically during the last two decades due to a combination of the removal of natural predators, changes in habitat, and adaptation to man-made environments.
Deer are very charismatic animals, and many people in New York enjoy seeing and watching deer. About 700,000 hunters pursue deer annually in the state, and contribute millions of dollars to rural communities. Although a highly valued species, the white-tailed deer has reached record population levels in many eastern states. Densities of more than 40 deer per square mile are often observed in regions of hardwood forests mixed with agricultural lands and greater than 100 deer per square mile may occupy suburban areas with woodland cover. Deer overpopulation is causing many conflicts, including human health and safety concerns, ecological impacts, and economic losses.
The human health and safety issues associated with deer are primarily deer-vehicle collisions, and transmission of Lyme disease. It is estimated that 29,000 people are injured and 211 lose their lives annually in deer-vehicle collisions in the United States. In addition, according to the Centers for Disease Control, the number of cases of Lyme disease is on the rise, increasing from approximately 2,000 cases in 1987 to 12,901 cases in 1997. Deer do not become infected with Lyme Disease, however, the adult "deer tick" prefers the deer as its host. Therefore, high densities of deer will support a greater abundance of "deer ticks", leading to an increased risk of Lyme disease.
Deer can also affect their own habitat and the abundance of other species. These effects may not be as obvious as impacts to human health and safety. Deer overpopulation can profoundly influence the presence, absence, and abundance of plants and other wildlife. In many forests, over-browsing of tree seedlings creates open, park-like stands with little or no vegetation near ground level. Instead of a diversity of woody and herbaceous plants, the ground surface may be dominated by ferns, grass, and woody shrub or tree species that are not preferred by deer. Wildflowers preferred by deer, such as various species of trillium and Canada mayflower, may be reduced in abundance or eliminated completely from forests where deer densities are high.
When the understory vegetation is reduced, forest songbirds may be affected. Some species may no longer inhabit an area, while others will be less abundant than they once were. When forests take on a park-like appearance, an important habitat component for forest songbirds is missing. There are fewer places to nest, and less vegetation means fewer insects for birds to feed on. Nesting in more open forests can make bird nests easier for predators to detect. Other wildlife such as squirrels, must compete for acorns, a preferred food of deer.
Deer frequently feed on some of the more economically valuable tree species in New York. Oak and sugar maple seedlings, as well as acorns, are preferred over less palatable species like American beech. Thus, less marketable species are more likely to survive to maturity, replacing the more valuable trees.
Forest landowners are not the only people experiencing economic losses from deer. Many farmers are losing a considerable amount of crops to deer. Homeowners are also becoming increasingly frustrated, as deer consume their ornamental shrubs and other landscape plantings. Overall, the economic impacts of deer over-population in the United States have become staggering. Annual estimates of deer damage reportedly exceed $2 billion nationwide, including $1 billion in car damages, > $100 million in crop damage, $750 million in damage to the timber industry, and > $250 million in damage to suburban landscape plantings and gardens.
If you are having problems with deer damage, you are not alone. A number of different solutions are available. However, there is no one, simple cure-all for deer damage, and the specific methods that can work will vary according to scale. For instance, methods that are appropriate for a home landscape of a few acres may fail in a large woodlot. Current alternatives include population reduction, exclusion, repellents, and cultural practices.
If you are a landowner with a large property and you feel that deer are overabundant, then population reduction may be achieved by hunting. However, removal of adult females is critical to reducing deer numbers. The only way to control a deer population and potential deer damage is by harvesting female deer. As a landowner, one way to achieve this objective would be to link permission to hunt on your property to removal of antlerless deer, allowing the taking of a buck only after the hunter takes a doe on your property.
In addition to traditional hunting, the NYS Department of Environmental Conservation is developing a Deer Management Assistance Program (DMAP) that can be used in conjunction with sport hunting to alleviate crop damage on farms. If you are a suburban homeowner, regardless of whether or not you perceive deer to be overabundant in your area, population reduction through traditional hunting methods may not be an option.
If deer are causing regeneration problems in your forest, decimating your fruit trees, or devouring your landscape plantings, then exclusion methods may be a viable alternative. Eight-foot high woven wire fences (Fig. 1) are the most effective method, however, they are also the most costly ($6-8 per linear foot) and many homeowners find them unattractive (Fig. 2). Electric fences can exclude deer if they are properly built and maintained, and they cost about 50% less than woven wire fence. When using electric fencing, a 7-strand design is recommended, with spacing of 8 inches or less between the lower wires (Fig.3.) The benefits of electric fencing are that they cost less to establish, are easy to construct, and are quite versatile. Disadvantages include safety concerns, and the need for increased maintenance and monitoring. For home gardens or landscape plantings, combining a single strand electric fence with strips of cloth and either attractants or repellents can be effective. Snow fencing can also be used to protect gardens or shrubs, however, most homeowners find them aesthetically unappealing. Many homeowners have had good success with lightweight plastic bird netting for protecting individual shrubs, and this material is nearly invisible at a distance (Fig. 4).
A number of commercial deer repellents are available. Use of repellents is not practical on a large scale, but can reduce browsing on individual shrubs or trees by 50-75%. Odor-based products are usually more effective than taste-based products. Hinder and BGR- Deer Away are some of the products that have been found to be effective. Most repellents have to be applied monthly for continued protection. If more than three applications of repellent are needed in a year, fencing may be a more cost-effective solution in the long-term.
Because deer have preferences for certain species of trees and shrubs over others, deer damage may be minimized by selecting species that are less favorable to deer. Species such as Japanese yew, American arborvitae, rhododendron and azaleas are heavily browsed by deer. Red cedar, firethorn, apple, and juniper receive moderate amounts of browsing. Other species, such as white birch, mountain laurel, American holly, shadbush, rose-of-Sharon, and white spruce, usually receive little browsing by deer. The amount of damage on any species will vary from site to site, and depend on other factors such as weather and availability of other food supplies.
When trying to reduce deer damage, feeding deer is not recommended. Feeding deer may increase the capacity for population growth, and leading to higher numbers of deer. In addition, attracting deer close to your property may make them more tolerant of people and less afraid to spend time next to your home, munching shrubs and garden plants.
Overall, using a combination of different methods is the most effective way of preventing damage. For landowners with large areas of land, population reduction and fencing are the only effective alternatives. For smaller parcels, a combination of fencing and repellents, or fencing, repellents and cultural methods, may provide relief from deer damage.
Beavers create ponds by constructing dams of sticks and mud. Within the ponds, they construct lodges that provide cover and protection from predators. In addition, they often store their winter food cache underwater, and develop a system of canals to provide quick escape routes from predators and to transport food and building materials.
Domestic dogs, coyotes, bears, and bobcats will prey on beavers if the opportunity arises. However, because they rarely travel far from water, beavers remain relatively safe from most predators. Natural predation usually has little effect on beaver populations in New York.
Beaver populations have increased in New York due to changes in land use patterns across the state. Abandonment of farmland and a subsequent increase in the amount of forest cover has provided more beaver habitat. In addition to increasing habitat, a decline in trapping interest has also contributed to higher beaver populations.
Impoundments created by beaver can produce wetland habitats beneficial to a variety of waterfowl, songbird, and amphibian species. Numerous mammals may also benefit from the creation of wetland habitat including, mink, otter, muskrat and raccoons. Wetlands constructed by beaver can also reduce downstream flooding during storm events by trapping and storing excess water. Therefore, beaver can provide many valuable ecological benefits.
At times, however, the beaver's dam building activity can produce undesirable results. The New York Department of Environmental Conservation receives about 2, 200 complaints about beaver each year, and it is estimated that costs associated with beaver damage exceed $6 million annually. Beaver may flood upstream land or threaten downstream property, kill trees or crops or damage them by flooding, flood homes, flood highways or railroads by plugging road culverts, and impair drainage systems or wells.
Solving beaver problems can be difficult because the beaver causing damage to your land may construct a dam on your neighbors property. That person may enjoy having beaver live on his/her property and may value the wetland habitat created. In such instances, it may be necessary for you to work with your neighbor to find a solution. If a plugged road culvert causes flooding on your property, you may have to work with the New York Department of Transportation or local municipalities to solve the problem. However, if the beaver in question is located on your property, you have several options. In some cases, preventing beaver damage through fencing, or protecting road culverts against blocking may be suitable options. In other cases, removal of the beaver or dam may be needed, which requires permits from the NYS Department of Environmental Conservation.
The first step in assessing what steps to take is to determine the magnitude of the problem. For instance, are beaver girdling or felling trees of economic value, or are they felling low-value trees? If you are uncertain about the species of trees involved and the value of those trees, first consult a forester to determine whether or not there is reason for concern. If you have just a few individual trees or shrubs on your property that you would like to protect, you may consider fencing. Loosely wrap welded wire fencing, or roofing felt, secured with string or wire, around individual trees and shrubs. Fencing should be a minimum height of 36 inches. Groups of trees can be protected with 36-inch high welded wire or woven wire fence, or with 12-inch high electric fencing with a minimum of 3 strands of wire spaced at 4-inch intervals.
Removal of Beaver or Beaver Dams
If large areas of your property are being flooded and small-scale solutions are not an option, then removal of either the beavers or the beaver dam may be necessary (Fig. 5). During the open trapping season for beaver, you may engage a trapper to remove beaver. In much of NYS, the trapping season runs from late November or December through January to April, when beaver pelts are at their prime. If you cannot locate a trapper to voluntarily remove beaver, you may contact a nuisance wildlife control person who will charge a fee for removing the beaver. Outside of the regular trapping season, a permit must be obtained from the NYS Department of Environmental Conservation to trap beaver. In addition, a permit is required to remove beaver dams or lodges. If the beavers are not killed, dam removal is a very short-term solution, as it will usually be rebuilt quickly. Pond draining is most likely to be successful in the summer, when less water is available to refill drained ponds. Once beavers are removed and dams are broken, as much of the dam should be removed as possible, or new animals may use the materials to construct another dam. It is also a good idea to remove the beaver lodge as well.
If you are having problems with beaver clogging a culvert on your own private road, or if you would like to prevent that from occurring, there are a couple options. If beaver have built, or are attempting to build, a dam inside a culvert, you may choose to install a pitchfork-shaped guard made of heavy steel rods in front of the culvert. This type of guard is installed by pushing the device into the substrate to hold it in place in front of the culvert. The second option is to install a deep water fence in a rectangular or D-shape around the upstream side of the culvert (Fig. 6). Devices such as these require continual monitoring and maintenance to remove any debris. The best long-term solution to plugged culverts is to replace small culverts with culverts of 2- to 3- yards in diameter(Fig. 7). Beavers are much less likely to attempt to block large culverts than small culverts. However, installing large culverts can be costly, and in some cases may require changes in roadway design to accommodate the larger size. Low-profile concrete box culverts may not require changes to the roadway.
Curtis, P. D., and M. E. Richmond. 1994. Reducing deer damage to home gardens and landscape plantings. Cornell University, Department of Natural Resources, Ithaca, NY 14853. 22 pp.
Hamlin, D., D. Dougherty, G. Fuerst, D. Jenks, T. Raffaldi, V. Gilligan, G. Golja, and B. Tuller. 1997. Beaver damage control techniques manual. New York State Department of Environmental Conservation, Bureau of Wildlife. 40 pp.
DEC Regional Offices and Sub-Offices
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