The recent discovery of a white-tailed deer infected with chronic wasting disease brought new urgency to deer culling at seven Forest Preserve District of Will County sites.
The district initially planned removal of 206 deer – primarily does and males without antlers – for its 2013-14 fall-winter season, according to Executive Director Marcella DeMauro.
Another 20 deer from Kankakee Sands Preserve near Braidwood were added to the quota after the disease was discovered in a deer shot there Dec. 19, DeMauro said.
Chronic wasting disease is an always-fatal degenerative neural disease that afflicts deer and elk.
“This is the first instance in Will County as far as we know,” said Glen Buckner, the district’s wildlife ecologist. “It’s similar to mad cow disease.”
The disease first was discovered in white tailed deer in north central Illinois in 2002, according to the Illinois Department of Natural Resources.
The disease generally spreads from deer to deer, but also can be present in the soil from deer carcasses in the wild.
“It can be taken up by plants and passed on to other deer,” Buckner said. “It’s a pretty pervasive disease.”
Unlike mad cow disease, however, there’s no evidence that humans are susceptible to the disease. Still, the state isn’t taking any chances.
“IDNR takes a very aggressive approach to managing the spread of chronic wasting disease,” DeMauro said.
IDNR policy to slow transmission of the disease has been to cull areas where infected animals are discovered, the same practice used by the district to manage the burgeoning herds in its preserves.
Local deer population density estimates range from 33 deer per square mile at Lockport Nature Preserve to a staggering 111 animals per square mile at McKinley Woods Preserve in Channahon, according to Buckner.
The district would like to see the herds eventually reduced to about 20 to 30 deer per square mile.
Yet despite three seasons of culling, deer populations remain so large at five of the preserves – McKinley Woods, Kankakee Sands, Goodenow Grove and Hickory Creek – that additional deer removal will be necessary for years to come, DeMauro said.
While the district depends primarily on aerial surveys for its deer count, the growing number of sightings from nearby residents also provides some sense of how pervasive the herds are, DeMauro said.
“If people are seeing deer that frequently, that’s not normal,” DeMauro said.
Part of the problem is that because of residential and commercial development, there’s really nowhere else for the deer to go.
“They’re pretty much restricted to the preserves and the cornfields,” Buckner said. “You have a high population and not much habitat for them.”
Large populations can cause a lot of grazing damage to trees and shrubs in the preserves, as well as to crops in adjacent farmlands.
Deer will feed selectively on their favorite foods, and then move on to their next, and so on, DeMauro said. Favorite flora include native lilies, orchids, native woody plants and shrubs, and young oak trees.
“Deer pretty much do nothing but eat,” Buckner said. “If you drive along a forest preserve, especially in Cook County, there’s a very clear line you can see where all the trees and shrubs have been eaten up to 5 or 6 feet. That’s the browse line.”
In addition to the plant damage, over-browsing can destroy habitat for other birds and animals.
The district has used sharpshooters to control deer populations since 2010.
This year’s regular culling season ended Feb. 23, Buckner said. The secondary culling at Kankakee Sands was expected to be completed last week.