Deer Management by the Numbers

Do you have an interest in deer management in Illinois? There are two new tools available which allow you to query recent deer harvest data and track deer statistics. The White-tailed Deer Illinois website hosts the Interactive Harvest Data and Deer Management Statistics pages. Both tools can also be found on the deer page of the Hunt Illinois website. Before we dive into the whistles and bells though, a primer on the “why” and “how” of deer management in Illinois might be useful for context.

Management of the white-tailed deer population in Illinois is the responsibility of the Illinois Department of Natural Resources (IDNR) Division of Wildlife Resources. Their deer management goals are to maintain a healthy deer herd that can exist in perpetuity and to provide recreational opportunities for hunters and wildlife watchers. To achieve these goals biologists must also balance people’s broad range of values and their varying concerns about disease transmission, crop damage, deer–vehicle accidents, damage to private landscapes and impacts on natural ecosystems caused by an over-abundance of deer.

Deer management must consider a variety of biological, environmental and sociological factors. This is because white-tailed deer can easily exceed their carrying capacity—the number of living organisms an area can support indefinitely without degrading their habitat. In Illinois an abundant deer population is due to usually mild winters and the ample food sources available, particularly in agricultural areas where deer have access to corn and soybeans. Also, in Illinois there are no longer populations of large carnivores, such as mountain lions or wolves, to naturally keep deer numbers within carrying capacity. 

Keeping deer numbers within carrying capacity is important because too many deer in an area can cause a variety of problems. In agricultural areas deer can damage crops and orchards. In urban areas they can quickly wipe out gardens or damage ornamental plants and other landscaping. And more deer on the landscape means a greater chance of deer–vehicle accidents (DVAs). In natural areas, deer can change the structure of the local plant community. When deer become overabundant, they over browse the local vegetation which reduces the regeneration of trees and allows more sunlight to reach the forest floor. Over time this can lead to a change in plant species composition, shifting away from native plant communities to ones dominated by non-native, invasive species. Another consequence of too many deer within a small area is disease transmission. Some diseases, such as chronic wasting disease, are spread from deer to deer by direct contact or at contaminated feeding areas; both scenarios occur more often as deer herds exceed the carrying capacity of an area.

Without large predators to maintain the deer population at or below carrying capacity, a well-managed state hunting program is needed to keep deer from becoming overabundant. But how many deer can or should the landscape support?

In 2008, the legislative Joint Task Force on Deer Population Control submitted recommendations on deer management to the IDNR. Their recommendations included adopting new deer management goals, lengthening the late-winter antlerless deer season and archery season, and making various hunting permits more readily available through over-the-counter sales.

The Joint Task Force identified DVAs in Illinois as a primary concern. A higher number of DVAs is frequently pointed to as evidence of deer overpopulation. From 2001 through 2008, the number of DVAs occurring each year throughout the state ranged from a low of 22,933 to a high of 25,847. Although the trend in number of DVAs during the five years prior to 2008 was not increasing, the accident numbers were considerably higher than during the 1990s, when DVA levels averaged about 17,000 per year.

Since DVAs are one of the major conflicts caused by an abundance of deer, it is logical to use DVA rates, rather than just using specific numbers of deer or deer densities, as a measure to judge whether management is maintaining deer populations at acceptable levels. IDNR biologists considered many factors and developed a simple, yet effective, approach to deer management—by dividing the number of accidents by the number of vehicle miles travelled, biologists developed a deer–vehicle accident rate goal for each county.

Each of the 102 counties in Illinois is assigned a goal for maintaining the deer–vehicle accident level at or below a set rate. Which means that more hunting permits are issued as the DVA rate increases and fewer permits are issued when deer abundance needs to be increased. With the Interactive Harvest Data tool you can see the annual deer harvest in comparison to DVAs (per billion miles travelled) since 2005. Each year the data will be updated on the site as it becomes available.

The Interactive Harvest Data tool also allows you to query the number of deer harvested statewide or per county by gender, age, hunting season and year. For those who like to compare deer stats, like checking the stats of your favorite sports teams, the Deer Management Statistics has you covered. This tool is the latest addition to the White-tailed Deer website and work is on-going to add even more data. While we’ve tried to be comprehensive, there may be other information you are looking for from the site. If that is the case, let us know. You can contact the author with suggestions about deer data you’d like to see included on the site.

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Laura Kammin is an Educational Programming Specialist with Lewis and Clark Community College. She formerly held positions at Illinois-Indiana Sea Grant, University of Illinois Extension, Prairie Rivers Network and the Illinois Natural History Survey. She received her master’s degree in wildlife ecology from the University of Illinois, Urbana-Champaign.