Soaring CWD numbers in southeastern Minnesota prompt DNR to stop culling deer

A startling increase in the prevalence of chronic wasting disease (CWD) in southeastern Minnesota’s deer population has triggered a new management response from the Department of Natural Resources that might surprise hunters.

Starting immediately, the agency will end its deployment of sharpshooters in all Driftless Area disease management zones. In previous winters, the shooters were sent to the area to curtail the spread of CWD by thinning whitetail herds in disease hot spots.

But now that CWD prevalence in the southeast part of the state has doubled in one year, to 5% or more, the benefit of offseason culling is considered too meager to justify the expense. The DNR is expected to formally announce the policy after the start of the new year.

“The positives have spiked,” DNR Wildlife Health Program Supervisor Michelle Carstensen said in an interview. “We are past the point where culling in the area will do any good. The gates are open and the horses are out.”

As a result, she said, computer modeling predicts CWD prevalence in wild deer in the area will climb to around 15% in 2028. Continued offseason culling at an expense of more than $800,000 a year would slow the spread, but only minimally, she said.

“Once disease is greater than 5% prevalence, and widespread, culling is not effective to curb the disease in that area,” Carstensen said.

CWD, a neurological disease that is always fatal in deer, is dreaded because of its proven potential to infect high percentages of deer, elk and moose. According to the U.S. Centers for Disease Control and Prevention, there is no direct evidence that CWD infects people. However, some experiments have raised the concern that CWD may pose a risk to people, and the agency has advised people not to eat CWD-infected deer.

Carstensen said the state’s program was hampered by a shortage of landowners willing to grant access for culling operations. She said she doesn’t blame landowners for their reluctance. But in a disease zone dominated by private land ownership, access to only 10% of the target area wasn’t enough to disrupt the transmission cycle of the disease, she said. Infected deer shed the disease in ways that put closely related deer at higher risk of getting it. The culling was always targeted in pockets of about 2 square miles where the disease was detected and where deer grouped together. But limited access left too many pockets of disease untouched and ripe for transmission.

From the beginning in 2010, when Minnesota wildlife officials started fighting CWD in Fillmore County, a sizable number of hunters expressed fears that culling and other aggressive harvest protocols would decimate the area’s prized deer herd.

According to computer modeling by Sergey Berg, an assistant professor of computer and information science at the University of St. Thomas in St. Paul, CWD in southeastern Minnesota could have been kept in check if more landowners allowed culling. Berg’s computer modeling indicated that prevalence would have been 1.63% in 2023 if culling had been doubled. If culling had been quadrupled, prevalence in 2023 would have been kept below 1%. Instead, it was 2.62% in 2023 and has now jumped to about 5.3%, according to Berg’s research.

According to statewide CWD testing by the DNR, the disease was detected this season in 85 deer. A whopping 72 of those cases were located in three close-knit hunting areas bordering Iowa or the Mississippi River. During last year’s hunting season, DNR surveillance of an even broader area in the southeast detected just 37 infected deer.

Carstensen said a hot spot in Winona County was previously considered its own separate area of disease. But in the past year, it has started to converge with the more-established area of disease around Preston and greater Fillmore County, she said. The disease is now considered endemic in the area.

Taylor Bestor, president of Bluffland Whitetails Association, a hunting and conservation group dedicated to preserving, protecting and promoting a healthy deer population in southeastern Minnesota, said this year’s CWD test results for the Driftless Area were “a little alarming.” He’s hoping the trend will awaken more hunters to the importance of other disease-management tactics to lower deer densities in the area. High densities contribute to CWD’s spread and crowd deer into ever-shrinking areas of good habitat.

“If you’re a deer hunter you should be into deer management,” Bestor said.

Bestor said the best strategy for deer hunters to slow the spread of CWD is to shoot more female deer, ultimately lowering the density of the area’s deer population. One way to achieve that goal, he said, would be for the DNR to require hunters to shoot a doe in order to earn a tag for a buck.

“Just hunting bucks doesn’t do it,” Bestor said.

Carstensen said the DNR hasn’t given up on fighting CWD in southeastern Minnesota. The DNR will continue to offer opportunities for extra postseason whitetail harvest to lower the area’s deer population. In addition, CWD testing will continue and the agency will keep restricting the movement of deer carcasses – a program designed to limit the spread of infectious prions shed by dead, CWD-positive deer. Deer feeding bans in the area also will continue. Feeders can artificially draw deer close to one another, increasing the risk of transmission.

“We need buy-in from the public,” Carstensen said. “They have a big role to play if they want to keep prevalence lower.”

She said the southeast would be worse off today if the DNR didn’t cull at all. The extra benefit of thinning deer populations with sharpshooters, instead of hunters, is that the professionals target deer most likely to be infected.

She said the DNR will resume winter culling operations in three other disease management zones beginning in February. Those locations are south of Lakeville, around Chubb Lake in Dakota County; around Merrifield in the Brainerd Lakes area; and just south of Grand Rapids. CWD has been detected in all three of those areas, and the DNR will be contacting landowners to seek more access for the sharpshooters.

“In all three of these areas the disease is emerging and culling can have the most effect,” Carstensen said.