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Scientific name: Odocoileus virginianus
Common name: 
White Tailed Deer

(Information in this Species Page was compiled by Alan Orth (Spring 2000), Luke Kemp (Spring 2002) and Julie Flaherty (Spring 2004) in Biology 220W at Penn State New Kensington)

The white tailed deer (Odocoileus virginianus) is the most abundant and the most widely visible large North American land mammal. It is an extremely adaptable species (there are 17 unique sub-species of O. virginianus in the continental United States alone!) and is found in a broad range of natural and human modified habitats. The geographic range of O. virginianus has expanded greatly during the past one hundred years. This expansion has brought the white tailed deer into contact and competition with a variety of other species including mule deer, moose, and elk. The outcomes of these interactions are typically detrimental to these contacted species.

Population Size
During O. virginianus geographic expansion, the overall size of its population also greatly increased. In 1900 there were estimated to be only 500,000 white tailed deer in the continental United States. Today, however, this population is estimated to be over 15,000,000 individuals! Individual deer have a range of a square mile or so but may share this range with several other individuals (as long as the food supply holds out!). The increasing number of deer in the United States has led to increased local population densities, severe overgrazing, and widespread destruction of both agricultural and landscape plants. As anyone who drives along Pennsylvania roads at night knows, there are a lot of deer out there!

Odocoileus virginianus
ranges in size from 27 to 45 inches in height (with a few individual bucks ("males") reaching 60 to 75 inches) and six to seven feet in length. Body weights also have a considerable range (from 80 to over 300 pounds!) with bucks being significantly larger than does (females). Individual differences in overall size are related to the quality of the food supply (agricultural foods are much richer and more nutritious than forest mast and gleanings) and geographic range (deer in the southern United States are smaller than those from the northern parts of the country). In Pennsylvania, larger individuals are typically found in the southern, more agriculturally developed, part of the state.

Life Span and Appearance
White tailed deer can live up to 15 years in the wild and up to 25 years in captivity. Most individuals, though, live a year or two at most.

Odocoileus virginianus has a coat that is reddish-brown or tan above (especially in the summer: this is referred to as the "red coat") and white on the underbelly, around the eyes and nose, inside its ears, on its throat and, of course, on the underside of its tail. In winter, the coat thickens and becomes darker in color often approaching grayish-brown in color (the "blue coat"). Fawns (immature O. virginianus) have white spots on a reddish brown coat. This pattern gives the fawns excellent camouflage.

Bucks are easily distinguished from does by the presence of antlers. Antlers  are hard, calcium rich structures that grow from glands on the tips of the buck's skull. They are distinctly bone-like but are not true bones. The antler's begin to grow each spring or early summer as the buck begins to feed on the nutritionally rich foods that come into great abundance. There is a relationship between the age of the buck and the quality and quantity of the foods he ingests and the subsequent size and complexity of the antlers.  Antlers are initially covered by soft skin and hair ("velvet") which will be shed in the fall typically as a consequence of the buck's vigorous rubbing against the ground or on tree branches or trunks and other vegetation. These buck rubs and ground scrapes also serve as sign to attract receptive does. Numerous trees along the Nature Trail have bark that has been rubbed smooth by bucks polishing their antlers and marking their territories. Antlers are used by the bucks in dominance interactions with other males. These interactions range from sparring to overt battles. The more dominant a male, the greater the likelihood and frequency of mating. Antlers are shed between December and April. Many animals (like rabbits and mice) consume the calcium and mineral rich antlers as an important part of their diet.

Mating and Reproduction
Prior to antler shedding, the does come into estrus causing the bucks to go into a frenzy of competitive behaviors and mate pursuits. These behaviors mark a time period referred to as "the rut." During the rut bucks tend not to eat but will, instead, spend most of their time battling other bucks and chasing and copulating with does. A doe going into estrus will be receptive for copulation for about 24 hours. If fertilization does occur during this time interval, the doe will go into estrus again in about a month.

Pregnancies last from 6 1/2 to 7 months so fawns conceived in November will be born in May or June. A doe, depending on her age and overall health, may have one to three fawns with twins being very common. The fawns are spotted and virtually scentless at birth and are able to stand and walk about almost immediately. The fawns feed on their mother's milk for several weeks and begin to explore their habitats to search for for food. At three to four weeks of age the fawns begin to follow the does and eat more and more solid food. Most fawns are weaned by four weeks although some continue to nurse for several months.

Impact on Habitat
White tailed deer are opportunistic grazers and gleaners that will consume almost any palatable, available food. In the spring and summer, green plants dominate their diets while in the fall, mast (acorns, beechnuts, etc) is very important. Almost all commercial crops grown in large or small agricultural systems are also consumed. Home gardeners, in particular, often go to great lengths to keep deer out of their gardens and away from their crops. In the winter, food becomes extremely scarce causing the deer to primarily rely on fat stores for energy. During this time of food deprivation, deer will begin to consume woody vegetation  (saplings, twigs, buds etc) in spite of its overall poor nutritional quality. Winter browse damage by deer can cause significant habitat deterioration in both natural and human-generated ecosystems. Forests in Pennsylvania, for example, under the stress of the huge winter white tailed deer herds, lose a considerable proportion of young trees every year. Seedlings that are less palatable to deer (like red maple and black cherry, for example) are becoming increasingly abundant and may eventually become the dominant tree species in our hardwood forests. Also, ferns (which are not eaten by deer) are growing more and more abundantly and lushly in the deer-impacted forests of Pennsylvania. White tailed deer, then, via their feeding habits and preferences, are re-sculpting the very nature and structure of our forest ecosystems.

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