Wildlife Deer Populations

Why Manage Deer?

Deer are an important part of Lake County's natural areas. Like other native species, they are beautiful and have a place in the ecosystem. But in some of our highest-quality preserves, their numbers are so high that habitats are becoming unbalanced. These large plant eaters are consuming a great number of plants. Left unchecked, this could lead to the loss of native plants and animals, including endangered species.

One of our key roles is to preserve a diversity of habitats for future generations. To maintain a balance between deer and other species, our policy is to reduce deer numbers in the most humane and effective way possible.

Why are the habitats unbalanced?

Deer habitat improved greatly as this region gradually became settled. The landscape now offers enough food and cover for deer to thrive. Coupled with the loss of predators, deer numbers have surged.

Our winters are not severe enough to reduce herds. Automobiles are the only significant "predator" of deer in Lake County. Humans can compound the problem by feeding deer, which may encourage the population to climb even more.

Most female deer start to produce offspring when they're just two years old. They breed for about 12 years, some having twins each year. Without natural predators this population growth greatly affects habitats.

How do we monitor the populations & impact?

Our wildlife biologists have put up "deer exclosures" at several preserves. Deer can't get into these fenced-off areas but squirrels, woodchucks and other plant eaters can. In nearby control areas, deer roam free. We measure and compare the plants in both areas to assess the impact deer have on the habitat.

Data collected since 1988 show that deer do pose a threat to the number and variety of plants. Also, those plants favored by deer are less vigorous and produce fewer flowers outside the exclosures. To see an exclosure, visit Ryerson Conservation Area. Plan your visit for spring, when differences are most apparent.

Humane removal

Deer are removed from several preserves under humane conditions by qualified sharpshooters. Work occurs when preserves are closed, and all venison is donated to Lake County charities. This is the best option now available and is used by agencies nationwide.

Deer numbers are estimated each winter with helicopter survey flights. Our average goal, dependent on habitat type, is 15 deer per square mile, based on published research recommendations. At that level, we have a better chance of sustaining habitat for other species.

District staff keeps up-to-date on developments in the field of deer management. This ensures that the District’s program is conducted using the most effective, efficient, and humane methods currently available. All methods used are approved by the Illinois Department of Natural Resources.

It's all connected

Deer management is just one part of our Natural Resource Management Program. We use several other safe and field-proven techniques to help restore balance in your Forest Preserves.

The District manages the preserves for the overall health of the ecosystem, and giving preference to one species would be irresponsible on our part. Deer are a valuable part of the ecosystem, and the District will not eliminate all deer from a preserve. The District’s goal is simply to maintain deer populations at sustainable levels to promote overall ecosystem health.

Overabundant white-tailed deer populations have the ability to drastically alter both plant and animal communities. Deer are voracious eaters and can eliminate understory vegetation, directly impacting the plant community. Reduced understory also decreases vegetative cover which serves as nesting locations for ground-nesting birds, cover for woodland frogs and salamanders, and sheltered resting sites for other wildlife species.

Ultimately, deer can reduce vegetation so much that they no longer have adequate food to sustain their own population. When this occurs many deer die from starvation.

Overabundant deer populations also increase the risk for disease transmission (e.g. Chronic Wasting Disease), parasite transmission (e.g. deer ticks which can carry the bacteria that causes Lyme disease), and deer-vehicle accidents.

Currently, the District only conducts deer management at three preserves in Lake County. At those preserves, the overall health of the deer herds has improved along with the quality and diversity of the plant communities.

Get additional information on living with white-tailed deer.