White-tailed Deer and Forest Health in Northern Virginia

by Bill Browning

Deer are a natural and beautiful part of our forest. They are Virginia’s largest herbivore, and despite their size, they are fast, agile, and graceful. They are an integral part of our ecosystem. However, their population has grown to the point where they unfortunately are overwhelming other species, degrading our forests, and harming the environment.

Population History

Deer helped fuel European settlement in the 17th-19th centuries. Our colonial ancestors hunted them for food and clothing, and even used deer skins (buckskins) as a form of money to trade for goods; the slang word for money, “buck,” comes from this era.

Virginia’s Department of Game and Inland Fisheries (DGIF) estimates that there were somewhere between 400,000 and 800,000 deer in Virginia in the early 1600s. We nearly extirpated them from the Commonwealth by the early 20th century as hunting and economic development drove them from our landscape. Deer became so scarce in Virginia that DGIF even had to import deer from the Midwest to satisfy the local hunting community.

During the latter part of the 20th century, as hunting declined and agricultural land was transformed into suburbia, the deer population exploded in our area. Deer are an “edge species” which means they prefer territory where natural woodland habitats meet encroaching human habitats. William McShea, a wildlife biologist with the National Zoo, says that “the eastern United States was [originally] one deep, dark forest. Now it’s deer nirvana. It’s one big edge.” Today, we likely have more than a million deer in Virginia.

More Deer Mean More Deer Browse

Deer are eating machines. An adult deer eats between 5-7 pounds of vegetation per day. Wildlife biologists at the National Park Service estimate that one square mile of a healthy forest can generate enough vegetation to feed about 15-20 deer. The jurisdiction of Arlington County, for example, has slightly more than one square mile of deer habitat (natural areas), suggesting that it can support little more than 15-20 deer in total. Many of us have spotted more than a dozen deer in our own neighborhoods, much less the whole county. The results are likely similar in other parts of Northern Virginia.

As a result of this overpopulation, deer are destroying the understories in our natural areas. Forest understories are vital for habitat and for ecosystem services. When the forest is degraded, there’s no place for many songbirds to build their nests and no cover for mammals and amphibians to hide from predators. Moreover, there’s less plant material to absorb rainfall, making the Chesapeake Bay more vulnerable to pollutant runoff and our urban neighborhoods more susceptible to occasional flooding.

Through selective feeding, deer affect forest plant communities by reducing tree seedling numbers, species composition, and seedling height. They also affect herbaceous plant composition as they browse on some species and ignore others. The Virginia Native Plant Society notes that deer browse removes hundreds of plants that provide food for insects, birds, and small animals that depend on them, such as orchids, trilliums, oaks, milkweeds, hickories, and blueberries.

A 2016 Penn State Extension Report notes that, when the deer population density exceeds what the land can support, forest regeneration suffers. Decades of overbrowsing by deer have so severely depleted the habitat that many residents have never seen a healthy forest understory. And it is this healthy forest understory that provides the environment from which future canopy trees can emerge. Richard Parker, regional director of the Genesee State Park Region (New York), said that “as the current forest dies, there will be nothing to replace it.” 

In the pair of photos below, the forest on the left provides food and habitat for many species of insects, birds, mammals, reptiles, and amphibians. This well-structured forest can filter sediment and pollutants out before the rainwater reaches the Chesapeake Bay. It can also generate enough seedlings to take over from the current canopy trees in the next generation. Conversely, the forest on the right is what we frequently see in northern Virginia where intense deer browsing means that any native plant that dares to poke itself up out of the ground is nipped off almost immediately by a deer passing by.

Too many deer are ruining our home gardens, defeating our park restoration efforts, and potentially endangering our health. They eat the plants we put in our yards unless we happen to have a dog patrolling the property or we spray deer repellent on our plants after every rain event. They eat the plants we install to restore our parks, unless we protect the plants with heavily fortified deer cages. And finally, as they wander through our parks and neighborhoods, they defecate where they please; deer can spread a variety of illnesses, such as giardia, in fecal matter that can end up in streams.

Too Many Deer Equals Unhealthy Deer

Many wildlife biologists argue that the deer have so decimated our local forests that they are unable to find sufficient food to remain well nourished. And while that fact may be debated by some other biologists, there is no disputing the fact that deer density is contributing to the spread of chronic wasting disease (CWD) which is similar to mad cow disease. CWD is transmitted through saliva and other fluids, and as deer congregate closer to one another, they are more likely to transmit this disease. CWD is insidious. Once infected, death is certain. CWD first showed up in white-tailed deer in 2001 in South Dakota and Nebraska. It has now spread to 24 states, including Virginia, where it appears to be migrating eastward from the West Virginian border.

Losing—and Regaining—Balance in our Deer Population

Human expansion and economic progress have driven natural predators out of Virginia, giving the deer free rein. We have not had effective predators for deer, such as wolves or mountain lions, in Virginia since the early 20th century. And other predators, such as foxes or coyotes, are ineffective. Foxes prefer smaller mammals and coyotes are unable to bring down anything but a small fawn. If you hear that a recovered fox or coyote carcass happens to have deer meat in their intestines, it most likely came from scavenging.

Given that human population and economic growth has allowed deer to expand in our area, we need human intervention to bring balance into the system. People frequently ask whether contraception or sterilization could be used as a humane way to control the deer population, but it is not humane. According to DGIF wildlife biologists, deer are susceptible to capture myopathy, also known as white muscle disease. This response to being captured, restrained, and handled causes the deer to build up lactic acid in their muscles. This lactic acid affects blood pH and can kill many of the internal organs, especially the heart. While some experts say it is possible to capture deer with low mortality rates in order to treat them with a contraceptive, it has not been shown to be effective in managing deer populations in an open environment. These methods require frequent follow up and can be quite costly. Further, DGIF only approves of medical intervention with deer for research, not for population management.

Given these limitations, local jurisdictions have adopted managed hunting as the best way to control the deer population in our area.

Fairfax County began an archery program after a librarian was killed in a car collision with a deer in 1997. The county’s managed hunting program now includes archery, shotguns, and high-powered rifles that has grown to cover about 100 of its county parks and properties (more than 80% of county parkland). The volunteer archers alone have culled about 1,000 deer per year since 2014 and the county donates venison to the Hunters for the Hungry program. Police and wildlife managers exercise strong oversight and there have been no safety incident or injuries to park patrons (or pets) since the program’s inception.

Montgomery County, MD manages archery, shotgun hunting, and sharpshooting operations in 54 parks, covering more than 50% of the county’s total park area. The county program began in the late 1990s, and hunters have removed over 19,500 deer from the parks and donated 315,000 pounds of venison to the Capital Area Food Bank. County police records document that collisions with deer have declined near the parks where culling takes place, and there have been no injuries to hunters or citizens as part of these programs.

The National Park Service began its Rock Creek Park deer management program in 2012 and uses professional sharpshooters to hunt at night when the park is closed to the public. Since March 2013, almost 400 deer have been removed from the park and over 10,000 pounds of venison has been donated to D.C. Central Kitchen, a non-profit organization that distributes meals to homeless shelters in the metro area. In the decade between 2009 and 2019, NPS estimates that in Rock Creek Park seedling numbers rose from 2,240 per hectare (2006-2009) to 5,960 per hectare (2016-2019). There have been no hunting accidents in the park.

Arlington County and the City of Alexandria do not have a deer management program at this time.

Perhaps some of our analysis can be best summarized by a quote from Aldo Leopold in the 1940s. Leopold was a wildlife biologist, a professor, and an early conservation thinker, who helped change our country’s land management approach from one of conquering the land to living in harmony with it. He wrote in A Sand County Almanac:

“just as a deer herd lives in mortal fear of its wolves, so does a mountain live in mortal fear of its deer. And perhaps with better cause, for while a buck pulled down by wolves can be replaced in two or three years, a range pulled down by too many deer may fail of replacement in as many decades.”

By ignoring the deer overpopulation problem, we are allowing the deer to degrade the environment at the expense of many other native species and the future of our forests.