MANAGING DAMAGE FROM DEER

Deer injury includes bark stripping, tramping and twig browsing. It is undesirable because it can result in loss of revenue. The deer damage problem can often be prevented. Trial and effort, combined with research, as resulted in 3 general deer damage control methods: (1) removal of deer; (2) frightening or repelling; and (3) exclusion. The best method will vary under different conditions and a combination of methods may be employed. Some factors relevant to a management decision are: tree age and height, area to be protected, abundance of deer, and the abundance of additional foods. Large revenue losses may prompt a land owner to spend more to prevent the damage than would small losses.

Deer injure young trees no taller than most deer can reach, mainly by eating the terminal bud. This ruins the form of the stem, and if growth of the stem continues, it lowers the value of the stem. Deer may also eat the tips of branches and damage unknown numbers of small tress by tramping the soil. Plantations growing seedlings of species favored as browse by deer invariably have effective fences or deterrents because of the large amount of damage that even a few deer can do. It has been observed that seedlings clipped below the cotyledons died. Dormant buds or lateral shoots are required for recovery. Planting seedlings deep with cotyledons just below the ground level may help reduce losses to deer (Shelton and Michael (2002)

In old trees, growing buds are out of reach of deer and damage such trees by stripping off the bark (which without killing it directly may provide access for disease and insects). During winter or other times of food scarcity, deer may kill a mature tree by girdling it. This is an uncommon occurrence because deer would rather eat more tasty available browse, and because they would probably move to another tree before completely girdling one. Damage to branches is of relatively little importance in wood production, but may be extremely important in orchards where fruit develops from flowers at the branch tips. Protecting individual trees is often tedious and is always time consuming, therefore it is usually practiced over small areas. The objective is to protect the growing stem "leader" until it can no longer be reached by deer. Favorable results have been obtained using sandpaper strips 5cm wide and 12cm long. Wrapping the sandpaper around the tip reduced damage from 95% to less than 14%. Plastic bags or plastic wrap have also given good results, and may be used to prevent bark stripping. Commercial repellents such as T.M.T.D., and Z.A.C., when applied by spraying or dipping, repel deer excellently, but their protective effects last only one year. Tankage, made from slaughterhouse waste, put in bags and hung from lower branches is effective, but needs to be replaced twice a year.

In the past, noise-makers have been used to repel deer from stands. Although initially effective, the deer tended to become accustomed to the noise and ignored it. Carbide cannons and M-80 firecrackers spaced on a slow-burning rope and hung from lower branches have been effective. Because these methods require frequent replacement or recharging, and may disturb neighbors at night, they are being replaced by more advanced and effective means of protection. One more effective and long-lasting solution is the use of a series of repellents interspersed along the perimeter of the stand to be protected. Often there is some kind of fence around the stand, and a combination of these methods increases their effectiveness. Nurseries and plantations may need a deer-proof fence around them. The cost is high, but maintenance is practically zero and it is effective for many years. Also, recent designs have proven to be 100% effective at lower costs than the previously used vertical fences. The new fences are slanted at approximately 45⁰, with the overhand on the outside.

The practice of eliminating deer to prevent them from inflicting injury to trees has long been used. The inherent ineffectiveness of this system has prompted the development of more effective methods. Eliminating animals is a poor method of preventing losses because only a small proportion can be eliminated. Killing the deer in one area simply allows deer from nearby areas to occupy and damage the original area.

In deciding upon a method of preventing deer damage, the most common limiting factor is available financing. The fact that price usually increases as effectiveness increases adds more complications to management decision-making. The costs of protecting an area should not exceed the losses that would be realized if there was no protection. Maintenance costs must also be considered, as well as the possibility of damage despite any preventative measures that have been used. It is important to know the extent of the deer damage before prevention is attempted. This knowledge is useful in deciding how much should be spent on prevention, as well as on control and maintenance.

In integrated vertebrate animal damage work, the strong premise is that physical change or injury of a plant by deer may be conspicuous, but determining whether damage has occurred requires more analysis. Damage includes financial and other loss resulting from the injury. If real, large, substantial financial or other loss over time is not evident, it may not be reasonable to spend time and money on controlling deer or their effects.

Sample Report (Partial):

Deer injury was evaluated. The last report dated December 3, 1999, [A value] estimated injury at the level of 56 [B value]. The changed, based on observations in 2 [C value] periods is about 2.1% [D value]. (No action other than monitoring seems needed now.) [E value]

If D is less than 4: No action other than monitoring seems needed now.

If D is greater or equal to 4: The rate of increase may be too great and damage may occur. Increased monitoring should be done to clarify the rate or to take direct action. Staff of the R* Deer and the R* Pest Force may be helpful in designing a strategy.

For deer damage from car strikes, also see Deer Notes

email , Nov 2003

WASHINGTON - Some 150 people die each year in more than 1.5 million traffic accidents involving collisions with deer, according to an insurance industry-funded report released Tuesday that puts the economic damage at $1.1 billion.

The study relied on federal and state records as well as academic studies on the issue to develop the national estimates. Researchers hired by the Insurance Institute for Highway Safety (news - web sites) to produce the report said theirs was the first to look at the accidents nationwide.

The report focuses on steps by local governments to reduce accidents and recommends fences and reducing deer herds as the most effective ways of keeping the animals off the roads.

The study notes frequent public opposition to herd reduction plans and says that fencing can be costly to maintain and disruptive to natural deer behavior.

Highway reflectors, high-pitched whistles, signs and other methods to prevent collisions show mixed results, the report says.

Wisconsin's Transportation Department relies heavily on driver education to limit deer accidents, and last week, at the start of deer mating season, announced a new program.

Even if motorists understand there is a hazard,agency spokesman Dennis Hughes said. people still hit them.

Already this year, seven people on motorcycles have died in collisions with deer, he said.

The government's auto safety agency, which records the cause of death in each vehicle accident, determined that about 154 people die each year from crashes involving wildlife.

The insurance report relied on state studies from Michigan and Minnesota to estimate that more than 90 percent of wildlife accidents are caused by deer.

Researchers reviewed studies from 1995 and 1997 in a publication by The Wildlife Society, a nonprofit scientific and education association, to estimate the annual number and cost of deer-related accidents.

The insurance group updated those figures by comparing them with a University of Wisconsin study this year that accounted for deer accidents in the upper Midwest.

References Shelton, M.G. and M.D. Cain. 2002 Recovery of 1-year old loblolly seedlings from simulated browse damage Canadian J. For. Research 32: 373-377.

This Web site is maintained by R. H. Giles, Jr.
Last revision January 17, 2000.