White-tailed deer are a common and welcome sight across Illinois, so much so they are our state’s mammal. However, in the early 20th century they had been practically eliminated from the state because of unregulated hunting and changes in land use, among other factors.

Once state officials realized deer had all but disappeared from Illinois, they quickly enacted game laws to protect them, but it would take 50 years for the deer population to recover enough that the state could support a deer hunting season, the Illinois State Museum reports.

Today, deer are abundant across Illinois. The highest population densities of deer in Illinois are in places with wooded land near major watersheds such as the Illinois, Kaskaskia, Mississippi and Rock rivers, as well as in the Shawnee Hills in southern Illinois, according to Wildlife Illinois. White-tailed deer are adaptable and, as a result, they also thrive in urban and suburban areas.

Ecological effects

^{(Photo courtesy of Mark Rupsis)}

Because white-tailed deer are among the largest herbivores in Illinois and elsewhere in their range, they have a significant impact on the plant life in their habitat areas, according to Animal Diversity Web. When their population is high, they can be detrimental to plant communities because they overbrowse on vegetation. Overbrowsing affects the availability of food sources for wildlife, threatening the well-being of the deer themselves as well as other animal species. Deer can also become a nuisance to homeowners by eating vegetable gardens and ornamental plants.

In Illinois, deer have only a few natural predators, namely coyotes and bobcats. Deer herds that reach high density levels tend to be in poor health and are prone to cyclic population fluctuations and catastrophic losses. Because of this, a regulated hunting season is an important means of controlling their population, Wildlife Illinois reports.

Mating and reproduction

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Mating season for deer begins in October and runs through January, with a peak in the middle of November, according to Wildlife Illinois. Does usually have one fawn in their first year of breeding and two, or sometimes three or four, in subsequent years. Fawns are typically born between late May and mid-June.

Fawns weigh just 4 pounds to 7 pounds at birth, but they can stand within a few hours. Does will often use the same spot to birth their fawns year after year, and they may sometimes pick what seem like unusual spots, such as porches or shallow window wells.

Does will leave their fawns for hours at a time while they are out looking for food, Animal Diversity Web reports. The fawns are hidden away, often camouflaged against the forest floor. If you find a fawn alone, do not touch it or move it. The doe will return soon to feed it.

When fawns are about 4 weeks old, they will begin to accompany their mothers on foraging trips. They will be fully weaned by about 8 weeks to 10 weeks old, Animal Diversity Web reports. Male deer will leave their mothers when they are about 1 year old, but females will stay with their mothers for two years.

Health risks

^{(Photo courtesy of Paul Dacko)}

In Illinois, deer are at risk of having several diseases, but most pose no risks to humans, Wildlife Illinois reports. Deer play a key role in the life cycle of the black-legged tick, which is also called the deer tick. These ticks can be carriers of the bacterium that causes Lyme disease, and deer can be hosts for the adult stage of the tick’s life cycle.

Deer do not transmit Lyme disease, but being in contact with deer can increase the likelihood of exposure to disease-carrying ticks, Wildlife Illinois reports. Humans can get Lyme disease when they are bit by a tick carrying the bacterium.

The biggest health concern for white-tailed deer populations in Illinois and elsewhere is chronic wasting disease, which causes fatal neurological degeneration in infected animals, according to Wildlife Illinois. Chronic wasting disease was first identified in Illinois in 2002 in Winnebago County, and since then it has been found in deer in 17 counties.

Chronic wasting disease is caused by a prion protein, and no evidence to date has shown that humans can contract the disease by eating meat from a deer with the illness. Still, though, the U.S. Centers for Disease Control and Prevention recommends that hunters and others take precautions when handling deer in areas where chronic wasting disease is known to occur.

Deer can also be infected with a viral infection called Epizootic Hemorrhagic Disease, which is transmitted through gnats, midges and other insects from the genus Culicoides. The illness causes fevers and internal bleeding in deer, and it is fatal, Wildlife Illinois reports. The impact on local deer populations varies from year to year because outbreaks are affected by weather and other factors that affect the populations of insects that transmit the disease.

Property owners and hunters who find dead or sick deer can report them to the state through an online form.

Problems and solutions

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Deer can become a nuisance when they feed on landscaping and ornamental plants and vegetable gardens. They eat a wide variety of plants, and when they are hungry they will eat almost any kind of available plant. Bucks can also sometimes damage tree trunks and other woody plants by rubbing their antlers on them.

You can prevent deer from becoming a problem in your yard by choosing plants that are less susceptible to browsing by deer, including prickly and thorny plants and those that produce a smell, Wildlife Illinois advises. In addition, the University of Illinois Extension maintains a list of deer-resistant perennials. Morton Arboretum also has a comprehensive list of trees, shrubs, herbs and other plants not favored by deer.

Fences can keep deer from entering your yard, but because they are such good jumpers, fences would need to be at least 8 feet tall to ensure they can’t access your yard, Wildlife Illinois advises.

Commercially sold repellents can help limit damage caused by deer browsing, but these products vary in effectiveness and must be reapplied after heavy precipitation, Wildlife Illinois reports. The usefulness of repellents also depends on the local deer population and the availability of other food sources. When deer are hungry, they will eat any available plant, even those that have had repellent applied.

In Illinois, white-tailed deer are protected as a game species under the Illinois Wildlife Code. You cannot remove deer from your property without a license or a permit, Wildlife Illinois advises. Homeowners should try to control damage from deer by modifying their landscape, installing fencing or using deer repellents. If these strategies are not successful, the Illinois Department of Natural Resources can assist with a deer removal permit.

All wildlife in Illinois are under the jurisdiction of the Illinois Department of Natural Resources. The Forest Preserve District of Will County does not treat, rescue or remove wildlife from public or private property. Both the Illinois Department of Natural Resources and Wildlife Illinois maintain lists of wildlife rehabilitators you can contact for assistance with injured wildlife.

(Lead image courtesy of Amy Miller)