University of Illinois Extension

Natural History

Description and Identification

A white-tailed deer buck grazing. Photo courtesy of the Illinois Department of Natural Resources.

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The white-tailed deer (Odocoileus virginianus) is the only native species of deer in Illinois. They stand 3 to 4 feet tall at the shoulder. Adult males (bucks) weigh 150 to 250 pounds, and adult females (does) weigh 100 to 150 pounds. During the summer the hair of both sexes is reddish brown to tan, and in winter is grayish-brown. The upper throat, belly, inner rump, and insides of the legs are white, as is the underside of the tail, thus the name "white-tailed" deer. Young-of-the-year (fawns) have a reddish coat with white spots that they molt at 3 to 5 months of age. Typically, only males have antlers, which, unlike horns, are grown and shed each year. Antlers begin developing in early spring and may be shed as early as December. However, bucks with good genetics and proper nutrition may retain their antlers well into March.

Behavior

Deer usually become active close to dusk when they leave their resting areas (beds) to go out and feed. Family groups include an adult doe, her fawn(s), and her female young from the previous year (matriarchy).   Some groups are comprised of multiple family groups. Bucks do not typically associate with the does except during the breeding season. Bucks may form small bachelor herds. Large numbers of deer may be seen together in areas of key habitat or at prime food sources, particularly during late winter when food can be in short supply.

Deer are often seen in herds during late winter. Photo courtesy of the Illinois Department of Natural Resources.

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Deer usually become active close to dusk when they leave their beds to go out and feed. They may rest during the night and forage again near dawn, or they may continue feeding throughout the night. During the winter, they may need to feed during the day to find enough food in areas where food resources are scarce.

Deer leave heart-shaped tracks. Photo courtesy of the Illinois Department of Natural Resources.

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Tracks

The heart-shaped tracks of white-tailed deer are easy to identify. There are no other wild animals that make similar tracks in Illinois. On soft ground, the foot may sink deep enough that the dewclaws may also make a mark. Another sign that deer are in the area is the presence of deer beds, trails, and, in some areas, browse lines. Additionally, during the fall breeding season (“rut”), bucks will rub trees and may make “scrapes” (small patches of disturbed ground that the buck urinates on to mark his territory).

White-tailed deer pellets in snow. Photo courtesy of the Illinois Department of Natural Resources.

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Droppings

White-tailed deer droppings are easy to identify. Deer leave piles of dark, cylindrical pellets ½ to 1 inch long. The droppings look similar to rabbit pellets, but deer pellets are larger and they leave much larger deposits of droppings.

Distribution and Abundance

White-tailed deer occur in every county of Illinois. There are more deer in Illinois today than when the European settlers first arrived. However, Illinois has not always had large deer populations. By the late 1800s, deer had been nearly extirpated from the state. Some isolated populations remained in the state, and others likely moved in from adjacent states, but the deer population remained very small. A restocking effort was begun in the 1930s. The deer population grew quickly due to better habitat (more edge habitat created by humans), the lack of predators (wolves and cougars had been extirpated), and a ban on deer hunting. By 1957, deer populations in Illinois had grown large enough to allow the first modern deer-hunting season in 33 counties. Some form of hunting, firearm or archery, now occurs in every county and the annual deer harvest exceeded 200,000 deer in 2005.

The highest densities of deer in Illinois are associated with wooded habitats along the watersheds of the major rivers, especially the Mississippi, Rock, Illinois, and Kaskaskia, and in the Shawnee Hills in southern Illinois. Very high densities of deer also occur in urban or suburban natural areas, remnant open spaces, and forest preserves that are closed to hunting. White-tailed deer are adaptable and opportunistic animals. They can live in areas with little natural vegetation, such as intensively farmed regions and suburban municipalities where they feed in residential areas.

Researchers have reported average home ranges of 0.44 square mile for does living in agricultural areas of Illinois and 0.17 square mile for does living in forest preserves near Chicago. Bucks tend to have larger home ranges than does.  However, the distances traveled by some deer during seasonal migrations or dispersals take them far outside of normal home ranges.

Habitat

Deer can cause serious damage in natural areas if they overbrowse the vegetation. Photo courtesy of the Illinois Department of Natural Resources.

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Illinois deer occur in or near wooded areas, particularly those along streams or adjacent to farmland. Deer frequently forage away from woods, but require wooded areas for survival (especially during the winter). Deer are a large, mobile, and behaviorally flexible species that can thrive in a variety of habitats that meet their needs for survival.

Food Habits

Deer are browsers in most of their range. Browsing is nibbling off the tender shoots, twigs, and leaves of trees, shrubs, and other plants with the deer's lower front teeth. In Illinois, farm crops and waste grain are an important part of the deer diet.

White-tailed deer will eat soybeans (and other crops) in addition to natural vegetation. Photo courtesy of the Illinois Department of Natural Resources.

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Additionally, deer eat many kinds of vines, grasses, and the green basal leaves of many woodland plants. Acorns, crabapples, and other fruits of trees and shrubs are preferred foods. In an urban environment, deer may damage plants in vegetable gardens or used in landscaping. Deer are ruminants and have a four-chambered stomach similar to cows. The first stomach chamber stores the food and starts the process of digestion. The moistened food then returns to the mouth for further chewing, a process known as chewing the cud. The cud is then swallowed and is further digested in the other stomach chambers.

Reproduction

Deer reproduction varies considerably in Illinois depending on habitat and local population size. White-tailed deer mate from October through January, with the peak occurring from late-October to mid-November. Gestation is about 7 months, and most fawns are born from late-May through mid-June. Female deer can have a fawn during their first year when habitat and population levels are favorable. Yearling does in good health can have twins, but generally have only one fawn. Adult does with good nutrition will generally have twins or even triplets.  Quadruplets have been observed but tend to be a rare event. Thus, it only takes a few years for deer populations to grow considerably in the absence of control measures such as hunting. Deer populations can double in size every other year.

Does often use the same fawning areas they used in previous years and may migrate some distance to isolated patches of woodland each year to give birth. Fawns weigh 4 to 7 pounds at birth and can stand and run slowly within a few hours.  However, for the first weeks of life, they avoid predation by remaining motionless in areas of cover; their spotted coat providing camouflage in the broken patterns of sunlight reaching the floor of wooded areas.

Does leave their fawns unattended for several hours at a time. However, the doe is nearby, even if she is out of sight. Photo courtesy of Willowbrook Wildlife Center.

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Sometimes fawns end up in strange places, such as in window wells or on sunny porch steps. If you find a fawn by itself do not move it. The doe is nearby, though not necessarily in sight. She will return to the fawn regularly so that it can nurse. The fawn and doe make sounds and use their sense of smell to help them locate each other. If the fawn is threatened, the doe will snort and stamp her front feet, and may charge the predator to drive it away. As the fawn grows and gets stronger, it will begin following the doe as she forages. Fawns are weaned at 4 to 5 months of age.

Longevity

A study conducted in hunted areas of central and northern Illinois reported average life spans of 5.5 years for does and 2.5 years for bucks. The oldest doe in the study was 18 years of age and the oldest buck was 9 years. The major sources of mortality in deer are hunting and collisions with vehicles.