Spotlight on Wildlife

Too Many Deer: The Ubiquitous Whitetail
Whitetail deer seem to be everywhere, grazing in meadows, dashing accross roads, raiding gardens. How can this animal survive, much less thrive, when its natural habitat is increasingly replaced by residential and commercial development? Unlike many species, whitetail deer fluorish in fragmented habitats. Unfortunately, they have become dangerously overpopulated as a result.

An edge-adapted species, the whitetail deer prefers forested areas that border open areas. These areas, which include farms and residential developments, provide deer with excellent sources of food. Shrubs, gardens, young trees and other residential landscaping plants are delicacies to deer. Nursery owners have a difficult time keeping deer from eating young plants and saplings. For farmers, deer can cause significant crop damage. A 1996 study conducted by Penn State University estimates that approximately $70 million in crops is lost to deer-related damage every year in Pennsylvania. Individual Pennsylvania farmers have lost an average of about $9,000 per year.

In the eastern United States, whitetail deer populations have increased because of the elimination of many of their natural predators. Wolves and coyotes no longer keep the deer population at healthy levels. Today, human beings (hunters and motorists) are the number one predator of whitetail deer. In 2001, 504,600 deer were killed by hunters in Pennsylvania, up from 144,415 in 1967.

According to the Pennsylvania Game Commision, approximately 5,000 deer are killed by vehicles each year. The owner of an auto body repair shop in Chadds Ford reports that between fall and early winter, the "rut", or mating season, he receives on average one request per day for car repairs due to deer-related accidents. During the rest of the year, he averages two to three per week. STate Farm Auto Insurance estimates that car repairs due to deer-related accidents cost approximately $2,000 but are often as high as $8,000.

Deer populations have grown so large that they have exceeded their ecological carrying capacity, the number of animals that the ecosystem can support. This situation is having a negative impacton the environment. For example, along wooded country roads, it is often easy to see a distinct line where all the vegetation ends- about four feet above the ground. This "browse line" indicates that the deer population has grown so large and dense that they have consumed most, if not all, of the understory vegetation. The resulting decrease in the overall plant diversity makes it difficult for the forest to regenerate. It also prevents forest succession in open areas and permits non-native invasive species to spread.

Disease is another concern. When the density of a species increases, diseases can become widespread. The increased density can effect other species as well. For example, Lyme disease, transferred by ticks that have bitten infected animals, is contagious to most mammals. Therefore, if more deer become infected, the chances of humans contracting the disease increase.

How can we address the problem of deer overpopulation? Although there are several ways, the most effective is to eliminate some deer. The Brandywine Conservancy permits deer hunting on Conservancy-owned lands including the Waterloo Mills preserve, Laurels Reserve and Miller Farm. On these properties, approved hunters must abide by specific rules. Only large bucks may be killed, thus allowing younger bucks to mature. This rule results in more does being taken and decreases the overall size of the herd.Hunters are allowed to use shotguns or bows - except at the Waterloo Preserve where only bow hunting is allowed. The Conservancy also requires hunters to take proficiency exams, undergo background checks (to ensure they have no past violations with the Game Commission), and perform four hours each year of volunteer work on the property where they hunt.

According to Waterloo Mills Preserve Manager Kevin Fryberger, this strategy is working. "When I started working at Waterloo Mills two years ago," said Fryberger, "I saw herds up to 30 deer. Now the largest herd I have seen has only 11, and hunters say they see fewer deer than they once did." At the Miller Farm, the Conservancy is inolved in a research project with the Quality Deer Management Association, a non-profit organization that researches and encourages hunting practices that improve the overall health of the deer population. It is hoped that this study will indicate that hunting is helping to maintain deer populations at ecologically-sustainable levels.

For more information about deer management, please contact the Brandywine Conservancy's Assistant Planner Wade Shelton at (610) 388-2700 or wshelton@brandywine.org.


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