Most residents of Virginia understand the need to change human land use practices to stop or minimize habitat destruction and preserve our native plant communities. An increasing number of people also support combating the spread of non-native invasive species to include problem plant species and insects such as the emerald ash borer beetle which girdles ash trees wiping out most trees in the genus Fraxinus across large land areas.
These two conservation priorities remain tremendously important, but there is a critical need to add another: controlling populations of white-tailed deer.
White-tailed deer, (Odocoileus virginianus), are beautiful animals, part of the natural fabric of North America, adaptive and graceful. Deer are prey species, requiring predators to keep their populations in check. Without predators removing at least 40% of a deer herd per year, deer populations quickly grow and they eat more of the plants, nuts and seeds than an ecosystem can sustain. “Ecological carrying capacity” is the term for the point at which the number of organisms in a species become so abundant that they alter the ecosystems they live in. White-tailed deer have exceeded theirs.
Humans arrived in North America over 13,000 years ago. We, not wolves and mountain lions, gradually became the top predator controlling populations of large herbivores. Many of those species eventually went extinct. Due to over-hunting, white-tailed deer nearly joined their ranks by about 1900.
In the mid-20th century, Virginia joined many other states in reintroducing white-tailed deer to supplement the few deer left and increase numbers for sport hunting. As reintroductions were carried out from the 1930s to the 1980s, two things happened that greatly contributed to the increase in the number of deer.
First, land use shifted away from agriculture toward suburban and urban uses. Contrary to commonly held beliefs, suburban landscapes do not take away deer habitat – they create it. Deer are adaptive animals. Suburban development creates preferred edge habitat for deer, and human landscapes provide high concentrations of edible plants close to the ground where the deer can get to them. You can grow more deer in suburbia than you can in a purely forested landscape. The same is true in rural areas where forests are broken up by agricultural fields, pastures, house lots and powerline easements.
The second major factor was a shift in how people view and interact with wildlife. As the 20th century progressed, more people lived in suburban and urban areas, and the number of people hunting dropped off, so there was reduced hunting pressure on deer herds. In 1942 the movie Bambi was released by Walt Disney. This film has influenced generations of Americans into believing that man is bad and all human interventions in nature are harmful. We now know how wrong the premises of that movie are. When you prevent fire from periodically visiting our natural areas and do not control large herbivores like deer, all species suffer and our natural heritage is impoverished.
Deer are a prey species that requires predation to control their populations. Without predation they can double their numbers in as little as one year. With abundant food in rural and suburban landscapes, and almost no hunting pressure in suburban areas and declining hunting pressure in rural areas, deer numbers have skyrocketed state-wide. In many areas of the state, deer population numbers are at more than three to eight times the densities that native plant communities can sustain.
I now suspect that 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.
-Aldo Leopold, Thinking Like a Mountain
Biologists began to notice impacts from excessive deer browse in some parts of the country as early as the 1940s. Research began in earnest in the 1970s. Staff from the Virginia Department of Game and Inland Fisheries estimates that the Virginia deer herd numbers about 1 million animals. White-tailed deer are large herbivores, needing about 5 pounds of forage a day, with each animal eating about a ton of leaves, shoots, twigs, seeds and nuts per year. That equates to over a million tons of Virginia’s biota being converted to deer biomass per year. There are more deer and less of everything else.
This is happening across the state, a widespread filter of browsing animals steadily impacting our native plants. If left unchecked, deer browse will remove hundreds of plants and thousands of insects and dozens of small animals that depend on them. The losers include orchids, trilliums, oaks, milkweeds, hickories, blueberries and many other plants that provide food and shelter to numerous insects and birds.
The winners include a shortlist of native plants such has hay-scented fern and a long list of invasive plant species that support few other species. The difference is one between a native landscape with numerous wildflowers through spring and summer, abuzz with activity, compared to a simplified green landscape, devoid of colorful flowers and the sound of forest dwelling birds – an impoverished environment.
Henry Wilbur, retired Professor of Botany at the University of Virginia, has been working for the past nine years to show the correlation of deer browse to native plant decline in controlled experiments at the Mountain Lake Biological Research Station in Giles County, Virginia. Professor Wilbur and his colleagues demonstrated that over an eight year period, deer browse began to reduce the total number of plant species and dramatically reduced the size, abundance and ability to reproduce for most of the forest herbaceous plants. This research shows that plant energy reserves are decimated as they try to grow with repeated browsing. Further research will be done to determine the rate at which these plants go extinct in a forest stand over time.
Researchers from Cornell University found that deer browsing not only removes many native plants from the forest ecosystems, but alters the seed bank so that those species cannot return and forest succession is impacted for hundreds of years. (DiTommaso, Antonio, et al; 2014.)
The result is that our remaining forest ecosystems are decimated. Deer eat everything native with few exceptions. They eat almost all of the non-woody plants in the forest as well as all shrubs and trees within their reach as well as the majority of the acorns and hickory nuts. They have now removed most vegetation from many of our forests below 5 feet.
The impacts include the loss of many of our woodland wildflowers, a change in forest stand composition to a few species such as tulip tree, American beech and red maple that have smaller seeds and appear to be less palatable to deer, and the disappearance of up to 75% of our forest bird species in many areas due to loss of the understory that provides them cover and the insect species they rely on for food.
Deer promote the spread of invasive plant species by transporting the seeds on their coats, hooves and in their feces, eliminating competition from native plants and disturbing soils. As our forests are oversimplified we lose native species, and once the existing trees die, there will be little to replace them except the few native species that deer find unpalatable and non-native species that provide little ecological benefit.
In 2008 the USDA Forest Service began to make dire predictions about eastern forests due to the over-browsing by white-tailed deer. The problem is so severe that even if we could reduce the number of deer immediately to within ecologically sustainable levels, it would take many decades if not centuries to recover our native plant communities.
If we act soon we can retain enough native plant stock and seed that many species could recover within remaining forests and repopulate surrounding areas over time.
This is even more critical in the face of climate change in the expected shift of species and communities across the landscape.
So what are we to do about it? Forest management professionals, advocating for the sustainable use and management of forest resources were clear: “To do this, white-tailed deer (Odocoileus virginianus) populations must be low enough to allow for the regeneration of forests and the development of desired plant communities and wildlife habitats.” (The Michigan Society of American Foresters 2006.)
To reduce the number of deer, people generally raise the prospects of reintroducing large predators, sterilizing deer or administering birth control to curb population growth, and using lethal control methods to include hunting and sharpshooting.
♦Predators – Attempts at reintroducing wolves in the western United States (gray wolves) and North Carolina (red wolves) have met significant resistance. Reintroducing large predators to the densely populated eastern United States is not viable. In addition, humans have been the dominant predator of white-tailed deer for at least 13,000 years.
♦Immunocontraception – Three studies have been undertaken in closed deer populations (those confined to islands or fenced compounds) to determine whether using contraceptives on deer would be effective at lowering populations. In all three (Fripp Island, SC; Fire Island National Seashore, NY; and National Institute for Standards and Technology, MD) there was some success in reducing the reproductive rates, but deer populations were never reduced below 100 to 200 deer per square mile – between five to ten times the ecological carrying capacity for eastern forests. (Rutledge, August 2012)
♦Sterilization – Efforts to sterilize white-tailed deer have demonstrated that although there could be some localized reduction over time, sterilized females remain in estrus, attracting more males in the near term and potentially increasing deer-vehicle collisions; sterilization programs would need to be preceded by lethal reduction of herds in advance to bring populations to more manageable levels (Boulanger, 2012); and multiple studies show that deer move in and out of study areas frustrating herd reduction efforts even in fenced compounds. (HSUS, 2013) (City of Fairfax, 2014)
♦Lethal Control – Monitoring of vegetation in areas where hunting has occurred over multiple years using various methods has demonstrated that lethal control of deer can result in recovery of herbaceous plants and production of large numbers of seedlings of woody plants. (Jenkins, 2014) (Author’s observations at Conway Robinson State Forest, Gainesville, VA)
Lethal control methods are the only deer population control option that have been shown to be effective. It is time for residents and local governments throughout Virginia to join with the Virginia Department of Game and Inland Fisheries, the Virginia Natural Heritage Program, large landowners and managers and others in supporting and urging efforts to reduce and manage the number of white-tailed deer in order to protect our native plant species, the communities in which they live and the animal species that depend on them.
The measure as to whether management efforts are successful must be based on recovery of our native flora which is the foundation for our natural communities. The Virginia Department of Game and Inland Fisheries is working with Virginia Tech to develop such a measurement tool. Efforts to measure impacts in long-term studies such as those at the Smithsonian Conservation Biology Institute in Front Royal, UVA’s Mountain Lake Biological Research Station, and College Woods near Lake Matoaka at the College of William and Mary will be critical for not only monitoring forest change and the impacts of deer browse, but also whether management efforts are successful.
The conversation needs to shift from deer to plants. We need to have fewer deer so we can have more of everything else – more native plants and the myriad of organisms they support. Call me selfish. I would rather share the land with a diverse assemblage – see trailing arbutus, thimbleweed and lady-slipper orchids; hear the call of ovenbirds.
VNPS Co-Registry Chair,
PWWS Conservation Chair,
Charles is a native of Virginia. He has a masters degree in Environmental Science from George Mason University, and a bachelor’s degree from the College of William and Mary. Charles served in the United States Army Infantry. He is a natural resource management professional with twenty three years experience in natural resource inventory, monitoring and restoration, to include fifteen years experience in deer management. Charles speaks to diverse audiences on topics ranging from native plants to ecological restoration, and is an instructor for three chapters of Virginia Master Naturalists.
“The current [deer] density is producing devastating and long-term effects on forests. Foraging deer “vacuum up” the seedlings of highly preferred species, reducing plant diversity and in the extreme, creating near mono-cultures. It could take decades or even hundreds of years to restore forests. . . . Deer have the capacity of changing forest ecology, by changing the direction of forest vegetation development. It doesn’t matter what forest values you want to preserve or enhance—whether deer hunting, animal rights, timber, recreation, or ecological integrity— deer are having dramatic, negative effects on all the values everyone holds dear.”
-Stephen Horsley, US Department of Agriculture Forest Service Researcher
(“The forest nobody knows.” Forest Science Review. Newtown Square, PA: USDA Forest Service Northeastern Research Station; Winter 2004(1), p. 4. http://www.fs.fed.us/ ne/newtown_square/publications/FSreview/ FSreview1_04.pdf. 29 May 2007).
Boulanger, Jason R., et al; Sterilization as an alternative deer control technique: a review; Human–Wildlife Interactions 6(2):273–282, Fall 2012.
City of Fairfax 2014 Sterilization Program Annual Report as provided to the Virginia Department of Game and Inland Fisheries.
DiTommaso, Antonio, et al; “Deer Browsing Delays Succession by Altering Aboveground Vegetation and Belowground Seed Banks;” PLOS ONE, Volume 9, Issue 3, e91155, March 2014.
Ellis, Bob, Editor; Virginia Deer Management Plan 2006-2015, Wildlife Information Publication No. 07-1; Virginia Department of Game and Inland Fisheries, Wildlife Division, June 2007.
Horsley, Stephen, US Department of Agriculture Forest Service Researcher;“The forest nobody knows.” Forest Science Review. Newtown Square, PA: USDA Forest Service Northeastern Research Station; Winter 2004(1), p. 4. http://www.fs.fed.us/ ne/newtown_square/publications/FSreview/ FSreview1_04.pdf. 29 May 2007.
Humane Society of the United States (HSUS); 2010, 2012 and 2013 Progress Reports [of the] Immunocontraception of White-tailed Deer at the National Institute of Standards and Technology, Gaithersburg, Maryland.
Jenkins, Lindsay H., et al; “Herbaceous layer response to 17 years of controlled deer hunting in forested natural areas;” Biological Conservation, 175, pp. 119–128, 2014.
Leopold, Aldo; “Thinking Like a Mountain;” A Sand County Almanac, p. 137; Oxford University Press, 1949.
Michigan Society of American Foresters 2006. Position statement on white-tailed deer in Michigan. http://michigansaf.org/Business/ PosStates/Deer.htm; 29 May 2007.
Rawinski, Thomas J.; “Impacts of White-Tailed Deer Overabundance in Forest Ecosystems: An Overview;” Northeastern Area State and Private Forestry Forest Service, U.S. Department of Agriculture Newtown Square, PA www.na.fs.fed.us ; June 2008.
Rutberg, Allen; Fact Sheet: PZP Immunocontraception for Deer; Tufts University Cummings School of Veterinary Medicine; August 2012.
Wilbur, Henry, PhD; “Oh Deer: How Perennial Woodland Herbs Survive the Overabundance of Whitetails;” Summary of research on white-tailed deer impacts on woodland herb species at the University of Virginia’s Mountain Lake Biological Research Station in Giles County, Virginia from 2006 to 2014; a presentation at the Virginia Native Plant Society annual winter workshop at the University of Richmond, March 7, 2015.