Human influences on white-tailed deer populations

White-tailed deer (Odocoileus virginianus) were found throughout much of the United States when Europeans first settled here. Their range most likely extended from the Eastern coast to modern-day Montana, Wyoming, Colorado, and Texas. Europeans described the great abundance of white-tailed deer in their early accounts of America (McCabe & McCabe 1984).

By the early twentieth century, deer were extirpated from much of their former range. Commercial hunting and deforestation were the primary causes of this eradication (Russel et al. 2001). In response to the declining deer populations, hunters encouraged state officials to manage the remaining deer (Revkin 2002). States set stricter deer hunting regulations and planned reintroduction programs. By the 1940s, deer were restored in much of the former range. Today, deer are found in all of their former range and are even extending their range westward (Russel et al. 2001). They are also an important economic resource. $10 billion a year is generated from hunting and wildlife watching of deer (Revkin 2002).

Recent land use changes have also encouraged an increase in white-tailed deer. Due to habitat loss and fragmentation, many large carnivores have been displaced. With the loss of predators, such as wolves, white-tailed deer have become abundant in many parts of the United States (Furedi & McGraw 2004). Furthermore, with increasing suburbanization, deer have more suitable habitat available for them. Deer may move seasonally from open canopy vegetation to forests. Low-density residential areas often provide this open canopy and forest edge habitat (Gaughan & DeStefano 2005). Gardens and landscaped lawns provide plants for deer to feed on and forest patches give deer hunter-free places to hide. As Dr. McShea, a wildlife biologist for the National Zoo, said, “ 'Deer are an edge species and the world is one big edge now” (Revkin 2002 ).

Because deer are increasingly found in habitats near humans, they are often described as a nuisance. It is estimated that deer cause over $1 billion in damage each year. This includes damage to property, crops, and timber. A single deer may consume a ton and a half of vegetation in one year. Furthermore, deer are associated with risk to people because they carry ticks with Lyme disease and cause thousands of car accidents each year (Revkin 2002 ).

By living in the suburbs, deer also pose management problems. Hunting cannot be used to regulate deer populations in these habitats. Yet even in rural landscapes where deer may be hunted, these animals may over-browse and damage forests, reducing the potential for marketable timber (Curtis et al. 2005). Overall, deer are a wildlife management success story. Today, however, they cause economic and ecological damage that managers must address in the near future.

Influences of white-tailed deer on ecosystems

The proliferation of white-tailed deer has had great consequences on ecosystems across the U.S. Scientists estimate that when densities of deer are greater than twenty per square mile, then the animals may degrade ecosystems (Revkin 2002). Many studies have reported how deer may affect woody plants, such as trees and shrubs. As herbivores, herds of deer may browse tree seedlings and prevent regeneration, change the dominant tree species through their grazing selection, and reduce species richness (Russel et al. 2001). For example, a decrease in Canada yew in eastern North America is predominately due to deer browsing (Allison 1990). Eastern hemlock and white cedar are also very susceptible to deer grazing (Alverson et al. 1988). Deer may also alter stem densities. For instance, several studies have shown that unbrowsed trees and shrubs often have smaller stem densities than browsed plants (Russel et al. 2001).

Deer also influence herbaceous plants. Deer may first affect the growth rate of plants. For instance, one study in Minnesota found that deer decreased the mean leaf area of the perennial herb Trillium grandiflorum. In areas of deer density greater than 25 deer/km2, the Trillium population was skewed towards smaller plants. In addition, deer grazing caused a 50% decrease in Trillium reproduction (Augustine & Frelich 1998). Deer may also modify seed dispersion. In a study of fruit-bearing plants in West Virginia, researchers found that deer grazed over 50% of the fruit in the study area. In some plant populations, deer completely consumed all the seeds generated that season. By examining seed count of American ginseng in deer pellets, the biologists further found that deer may be seed predators for American ginseng. Because these deer were also feeding on corn and grain, their digestive process most likely destroyed the seeds. The natural diet of deer, however, could result in less destructive chewing and a greater chance of seeds being found in pellets (Furedi & McGraw 2004).