Watershed Forests Hit by Deer Population Growing Pains

At the turn of the 20th century, market hunting had caused white-tailed deer (Odocoileus virginianus) populations to reach historic lows across the United States, with numbers hovering between an estimated 300,000 to 500,000 deer. In some areas white-tail deer disappeared completely, while in the Chesapeake region deer were usually only found along the extreme western edge of the watershed.

In 1900, Congressional passage of the Lacy Act prohibited the interstate trafficking of wild game, relieving pressure on deer populations. White-tails received further reprieve in 1908, when 41 states established departments of natural resources, which placed strict protections on the animals and instituted restocking programs.

Deer populations rose steadily in the following decades. While careful deer management by wildlife officials is partially responsible for the white-tails' rebound, deer also adapted to and prospered in the landscapes of America's sprawling suburbs. Mass development in the Bay watershed during the 1980s and 1990s carved up forests and farmland, creating “fringe” habitat that allowed white-tails to thrive. Some current estimates place the national white-tail population at 30 million. In Maryland alone, the 2005-2006 white-tail population was estimated at 269,000 deer.

White-tail deer are a favorite of many watershed residents and their resurgence has been greeted with enthusiasm by those who thrill at the sight of a big buck or a doe and her fawns. But when deer populations become too large, they can have a negative effect on their environment.

In the Bay ecosystem, the largest impact is the over-consumption of vegetation. Forest regeneration bears the brunt of the white-tail's voracious appetite as seedlings and shoots are usually consumed before they can grow to a size that can withstand occasional “browsing.” Over-consumption also impedes and distorts forests that are trying to recover from fire or logging. When forest habitats become over-browsed, deer naturally turn elsewhere to feed. Many homeowners experience this impact through the loss of ornamental plantings in the home landscape.

Large whitetail populations can also wipe out native vegetation such as shrubs and grasses, opening the way for noxious weeds and invasive plant species to take root. Deer usually prefer not to browse on non-native species if their traditional meals can be found, thereby perpetuating a vicious cycle.

An overabundance of whitetail deer can also substantially impact other wildlife in the area. Decreasing forest understory deprives essential food and cover to songbirds, reptiles and small mammals, which have a direct effect on the wildlife that count on those species to survive.

To learn more about whitetail deer and their influence on the Bay, attend the 30th Southeast Deer Study Group Meeting on Feb. 25-27, 2007 in Ocean City, Md. This year's theme will be “Deer and Ecosystem Impact.” For more information, please contact Doug Hotton, Deer Project Leader with Maryland Department of Natural Resources, at dhotton@dnr.state.md.us.