Riverwoods Preservation Council


The Buck Stops Here . . .
White-Tailed Deer Habits and Management

Jennifer Filipiak, Lake County Forest Preserve Wildlife Biologist

March 23, 2006



(photo courtesy of Greg Mancuso)

Deer prefer new growth. They tend to avoid grasses, thorny plants, and plants with strong odors.
When there is a shortage of their preferred food, deer will eat just about any vegetation.
Deer browse for acorns, bird seed, and whatever other food is available.
It is illegal to feed deer, since feeding may create reliance and may be unhealthy.
Deer eat spring ephemeral plants, and just about all other new growth, including saplings.
Deer eat the new buds, flowers and shoots, as well as landscaping.
Deer eat mature fruits and vegetables.

Doe herds usually comprise several generations, with oldest usually the leader. They herd for protection from predators. Bucks do not travel in herds.
Deer travel in large groups of multiple herds, usually with a single buck.
Bucks have no antlers. Does are pregnant.
The groups split up into herds. Does are looking for areas to bear their young (fawning areas). Bucks grow antlers, which at this time are extremely sensitive, prompting them to avoid heavily wooded areas.
Fawns are born in June, and are up on their feet within several weeks. Fawns have no odor, so they can hide effectively because predators cannot smell them. Because they cannot be smelled by predators, they are left alone for long hours while the does seek food. If touched by people, fawns will acquire human smell and become vulnerable to predators.
In open areas with no ground cover, coyotes eat about 95% of fawns. For that reason, woodlands are important for deer.
During this season, there is no hierarchy or competition among bucks.
Rutting occurs. Deer mark territories, by scraping trees and leaving a scent with their antlers, disturbing soil, and urinating. Competition among bucks becomes intense.
Late Fall 
Deer return to doe groups. Bucks lose their antlers. Does become pregnant, usually with twins. Sometimes even fawns have become pregnant.

Deer have a range of about one square mile. The range can vary significantly, however. Deer can travel 20-30 miles looking for new habitat. Deer are crepuscular – they travel most frequently in the twilight of dawn and dusk.

The Lake County Forest Preserve considers the range of Ryerson deer to extend south to Lake Cook Road, east to Portwine Road, and north to near the Wisconsin border. Natural barriers include the tollway, Lake Cook Road. Since deer swim very well, the Des Plaines River is not a barrier to travel.

The Lake County Forest Preserve monitors the deer population in Ryerson Woods, using aerial surveys and by monitoring the extent of certain plant life consumed by deer. Riverwoods falls within the “buffer area” for Ryerson – the area within which Ryerson deer may travel outside of Ryerson Woods. The Riverwoods deer population is a function of the population of Ryerson Woods. The Riverwoods deer population is also a function of the deer populations of other nearby areas not affected by Ryerson activities.

The deer density at Ryerson Woods is always greater than the target density. For that reason, the Lake County Forest Preserve has determined that deer control is necessary to preserve Ryerson Woods.

In around 1900, there were no deer in Illinois. The state legislature acted to protect deer and to introduce them to Illinois. Today there are about 800,000 deer in Illinois. Slightly over 100,000 deer are killed by hunters each year. About 23,000 each year are killed on roadways. Lake, Cook and DuPage Counties cull about 800 deer per year.

The life span of a deer is about 10 years. They typically die of old age, starvation or disease.

The deer population is cyclical, growing larger and larger until it cannot be supported by available food. At that time, the population crashes, with mass starvation. The population then begins to increase again, until the next crash. Today the deer population is nearing the top of the cycle.

The goal of the Lake County Forest Preserve is to establish and maintain a balanced and diversified habitat of native flora a fauna. The Forest Preserve employs biologists and other professionals to monitor the forest preserves.

Deer are at the bottom of the animal food chain, with no predators in this area. Coyotes attack only fawns and sick deer, but in insufficient numbers to control the deer population.

There are two basic types of control methods: non-lethal and lethal.
  1. Do nothing. Experts agree that without control, deforestation will continue and deer will cause irreparable damage to the woodlands environment. In addition, the inhumane cyclic population crash of deer will continue.
  2. Trap and release. It is a difficult process, traumatic to deer. The mortality rate is between 80% and 100%. There is no area available in which to release the deer. (A few years ago Highland Park tried surgical sterilization. The trial was considered unsuccessful and terminated early.)
  3. Immunocontraception. There is no approved or reliable method. All present methods are experimental. The most promising method requires two injections, two weeks apart. Injections would be required annually. Research continues to seek a single-injection method.

    UPDATE: In September 2009, the US EPA approved Gonacon as an immunocontraceptive for use with deer. It has not yet been approved in Illinois, and Ryerson has noted that its "effectiveness is questionable," especially in "free ranging deer." The EPA noted that Gonacon approval is for "hand injection only." The EPA also requires that Gonacon be injected on deer that have been captured and are being restrained. Finally, the EPA noted that "Gonacon is intended to be used in combination with other population management techniques since it cannot alone reduce already abundant populations." Click Here for the EPA's Gonacon fact sheet.
  1. Reintroduction of predators. This method is not socially acceptable.
  2. Archery hunting. Use of this method could not meet the population density goal experts agree upon.
  3. Controlled archery. This method involves hiring expert archers. Use of this method could not meet the population density goal.
  4. Sharpshooting. This is the only method the Lake County Forest Preserve has identified that would meet the population density goal. Culling occurs with professional sharpshooters. The Lake County Forest Preserve emphasizes safety and humane treatment. The deer are processed and donated to charity. About 1,000 families are fed each year by the Lake County Forest Preserve.
Note: unauthorized use of weapons in Riverwoods is illegal

CONCLUSION  The experts have reluctantly concluded that the only effective means of deer control today is culling. The Lake County Forest Preserve continues to do research in an effort to find a viable alternative to culling. Until another method is shown to work, culling is believed to be the only way to control the deer population in Ryerson Woods and preserve balance and diversity in the Ryerson Woods environment.

Activities in Ryerson Woods will not reduce the deer population in Riverwoods to appropriate levels, because Ryerson is not the sole source of deer in Riverwoods. Either an area-wide approach, or direct action in Riverwoods, is required. Riverwoods is taking no action at this time, and has not requested assistance from the Lake County Forest Preserve. The present do-nothing approach is having a disastrous effect on the Village’s woodlands.

© Riverwoods Preservation Council- - Page last updated: December 2009