Mike Purnell and his brother Lloyd concede they can’t find every carcass, skeleton or bone after deer die of chronic wasting disease on the family’s 700 acres of farmlands in southwestern Wisconsin.
But heading into December 2024, the Purnells hadn’t found any deer skeletons this year. They hope that means their aggressive approach to managing deer remains their best option. The Purnells found enough dead deer in 2019 and 2020 to pattern where CWD-infected whitetails usually die.
“We found 10 dead deer (in 2019), and eight more dead ones (by spring 2020),” Mike Purnell said. “We usually found them just inside the woods near a field with cut corn or other crops. It seems they come there to eat, but then can’t. They bed nearby and never get up again. One doe died in a field with food all around her.”
Purnell also thinks this year’s CWD tests aren’t all bad news. They’ve shot 20 deer as of Dec. 11, and although nine had CWD (45%), all the sick ones were bucks. Not one sick deer was a doe. Although a 45% CWD-infection rate is bad, they’ve seen it reach 55% on their four properties, with roughly half being does.
During the 2010s, the Purnells found deer bones and carcasses year-round. Dead deer deteriorate quickly, however, so the Purnells usually couldn’t collect lymph nodes to confirm infections. Still, Purnell thinks CWD killed most of them.
The Purnells test every deer they shoot with bows or guns. Generally, bucks more often get CWD than does. But not always. “(By 2018), gender didn’t matter on our land,” Purnell said. “If they were 2½ years or older, half of them had CWD. At first it was mainly older bucks, but then we started finding CWD in our 1½-year-old deer, so it definitely got worse. Why else would we suddenly find dead deer year-round?”
Reporting the Dead, Dying
CWD is thought to be caused by prions, a “corrupt” protein that accumulates in the deer’s nervous system, destroying neurons and brain cells until the deer dies. It has no cure, and its victims never recover. At best, CWD-resistant deer live about four months longer than other infected deer.
The Purnells aren’t the only Wisconsinites reporting sick, dying or dead deer. The Department of Natural Resources tracks reports from citizens who see listless, seemingly tame, or sickly “droolers and shakers.” From 2012 to 2019, the agency handled 1,451 sick-deer reports and tested 821 for CWD. Of those, 242 (29.4%) had CWD. From 2020 through late fall this year, the DNR logged 455 sickly deer, tested 362 and found 83 (23%) with CWD.
Those numbers don’t surprise Bryan Richards, CWD project leader at the U.S. Geological Survey’s National Wildlife Health Center in Madison. “That’s typical where disease prevalence is high,” Richards said.
Richards scoffs when skeptics say: “CWD didn’t kill those deer; bullets did.” Or “CWD didn’t kill those deer; starvation did.” Or “CWD didn’t kill them; pneumonia did.”
Richards said CWD makes deer more vulnerable to every threat, whether it’s other illnesses, bowhunters, gun-hunters, four-legged predators, or collisions with motor vehicles.
“It only makes sense that deer become less aware as prions destroy neurons and brain cells,” Richards said. “It’s hard to prove CWD makes deer less wary or slower to respond to threats, but the research shows that once deer get CWD, they’re more likely than healthy deer to die by the end of hunting season.”
Richards is referring to a Wisconsin DNR study that showed CWD-afflicted deer die at much higher rates than healthy deer. Data in 2017 showed deer with CWD had a 75% annual mortality rate, while 2018 data put the annual mortality rate at 65%. Similar studies in Wyoming put annual mortality rates at 68% for mule deer with CWD, and 60% for whitetails with CWD.
Either way, CWD is 100% fatal for deer that contract it, and causes them to die sooner from everything else they catch or encounter. Still, Richards understands why people are skeptical when CWD appears. It spreads slowly, and few people recognize its evidence because infected deer look normal until their final month. And when they die, decay and scavengers quickly recycle their remains.
The Purnells’ four properties, for example, seemed CWD-free 20 years ago. These lands are 50 miles west of Madison, and 25 miles northwest of CWD’s epicenter in Dane and Iowa counties, where the disease was first detected in February 2002.
Despite 5,745 CWD tests in Richland County from 2002 to 2006 — a 1,150 annual average — the Wisconsin DNR found only one case in 2002 and two cases in 2005. The agency found no cases there in 2003, 2004, 2006, 2007 and 2008.
Seeing no growing threat, lawmakers slashed the DNR’s CWD budget in 2007. Unfortunately, CWD had already taken hold. After hunters provided 660 samples in 2010, the state veterinary lab confirmed 11 cases (1.6%). By 2019, 1,457 samples produced 246 (17%) CWD cases. And this year, the county’s 34% detection rate leads the state.
Impacts Now Obvious
Purnell said Richland County’s deer numbers were beyond control by 2015 as hunter numbers and hunting pressure fell. But when CWD rates on their properties peaked at 55% in the early 2020s, they found more dead deer while seeing fewer living deer and fewer old deer.
“(In 2020) I found three dead 2½-year-old 8-pointers,” Purnell said. “Our hunters shot 40 deer in 2018 but only 26 deer in 2020, and 20 deer this year. Observations are down, too. It looks like Mother Nature is controlling the herd for us.”
Although Purnell thinks aggressive management helped reduce CWD rates on his land, he knows some neighbors try to protect does and want the Purnells to back off. He disagrees with the passive approach.
“If they (neighbors) would’ve shot more deer, these problems wouldn’t be so bad,” he said. “A lot of our neighbors don’t hunt, or they hold out for big bucks. Few of them test their deer. By ignoring it, they let CWD reduce the herd, so now hardly anyone sees deer 4½ or older. I’d say our deer numbers are 25% of what they were 10 years ago. If we had reduced the herd by hunting, we could have slowed the disease and had some old bucks to hunt each year.”
Richards said “things get ugly” when CWD, not hunting, reduces deer numbers. Hunters drag deer off the landscape and put more deer bones into landfills. Deer killed by CWD remain in the field, their carcasses contaminating soils and plants with prions.
Even so, Purnell said his group still enjoys deer hunting. They host 35 hunters each fall, and hold special hunts by youngsters and handicapped hunters.
“We’ve gotten back to deer hunting, but not big-buck hunting,” Purnell said. “It’s different without the big bucks, but we’re happy. We make it about camaraderie, and we’re protecting our forests. Ten years ago, deer were devouring our trees. Our latest planting was 6,400 trees, and they’re growing much better than before.”
