Managing deer in school and business environments

Deer become a problem on the grounds of schools and other facilities when they eat ornamental vegetation or damage trees by rubbing their antlers on the bark. There are three main species of deer: white-tailed deer, which live throughout the US, black-tailed deer, distributed mainly along the Pacific coast, and mule deer, found primarily in the West.

According to Scott Hygnstrom, professor and extension wildlife specialist at the University of Nebraska-Lincoln, an appropriate tolerance level is 30-35 deer per square mile. Besides seeing deer on the property, a common sign of deer damage is plants that are broken off unevenly. Deer have no upper incisors so they must tear their food, leaving twigs and stems looking ragged.

“There are no silver bullets or magic potions when it comes to deer damage management,” comments Hygnstrom. Tactics include habitat modification, repellents, frightening devices and manual population reduction.

Cornell Cooperative Extension created a fact sheet that lists ornamental plants categorized by their susceptibility to deer damage. Some plants that are listed as “rarely damaged” by deer are Barberry, Common Birch, Common Boxwood and American Holly. If possible, choose plants that are native to your area to reduce maintenance requirements. Check with your local extension office for more recommendations.

Exclusion can include cylinders around small seedlings or young trees. “This is one of the better approaches in dealing with deer because you can physically keep them from the resources that you want to protect,” says Hygnstrom. Cylinders can be made from sheep wire, woven wire, or any other type of wire that is convenient, or they can be purchased. They will have limited benefit as the trees grow because deer can reach up about six feet high when grazing.

Fencing is another option to keep deer out. Hygnstrom calls the woven wire fence the “Cadillac of deer fences” because it excludes deer very well. However, it costs $5-10 per foot in materials and about the same in labor. To be effective, fencing must be eight to ten feet high. Electrified high-tensile wire fences are a cheaper option. “These fences become not only a physical barrier but also a psychological barrier,” says Hygnstrom. Electrified polytape can also be used, but Hygnstrom recommends spreading peanut butter at regular intervals along the tape to attract the deer. Once they have licked the tape, they will associate that area with pain and may be less likely to return. Use extreme caution with electrified fencing in the vicinity of school buildings; it should only be used in areas where children will not go and should be clearly marked as electrified.

Repellents can be used to cause pain or fear. Hot sauce animal repellent (capsaicin is the active ingredient) and ammonia products cause pain when eaten or smelled, and coyote urine products may make deer think predators are lurking nearby. Deer Away, which contains putrescent egg solids (i.e., rotten eggs), has been effective in several studies.

“Deer acclimate quickly to frightening devices, especially the auditory varieties that go off in a repetitive pattern,” notes Hygnstrom. Auditory frightening devices can include propane cannons, pyrotechnics and sirens. Visual devices include effigies, scarecrows and lasers. A deer-activated bio-acoustic device has shown some efficacy in studies.

There are no toxicants registered for use on deer. Surgical sterilization and immunocontraception are options for fertility control, but are very expensive and do not reduce the population immediately. Many states do not allow translocation of white-tailed deer because habitats have filled and there is a risk of disease spread, warns Hygnstrom. Additionally, studies have shown that up to 80% of translocated deer die within six months.

Deer damage management is a community decision. All affected parties should be included in the discussion about management options. “You should try to reach a consensus but often you can’t,” comments Hygnstrom. “The community has to make a decision anyway, and move forward with that decision.”

For more information, see a recent webinar hosted by the Urban CoP eXtension.

From the School IPM 2015 July Newsletter

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