CWD: No Shortage of Deer Bones and Bodies

April 27, 2020 | by Patrick Durkin

Mike Purnell and his brother Lloyd concede they don’t find every carcass or scattered-bone pile after deer die of chronic wasting disease on their southwestern Wisconsin properties.

These two hunters, however, found enough dead deer the past two years to notice patterns on where whitetails die when CWD worsened on their Richland County farmlands.

“We found 10 dead deer a year ago, and we’ve already found eight this year,” Mike Purnell said. “We usually find them just inside the woods, near a field with cut corn or other crops. It’s like they come there to eat, but then can’t, and bed nearby and never get up again. One doe we found this winter died in the field with food all around her.”

CWD is thought to be caused by prions, a “corrupt” protein that accumulate in the deer’s nervous system, destroying neurons and brain cells until the animal dies. It has no cure, and its victims never recover. At best, deer with some resistance to CWD live about four months longer than most deer that contract it.

The Purnells find whitetail bones and carcasses year-round, whether while hunting turkeys or morel mushrooms in spring, when walking or scouting in summer or winter, or while bowhunting and gun-hunting in autumn. Dead deer deteriorate quickly, however, so the Purnells haven’t collected lymph nodes to confirm CWD in the dead deer. But Mike Purnell thinks it’s safe to assume CWD killed most of them. They test every deer they shoot with bows or guns on their 700 acres, and it’s a 50-50 coin flip whether their deer tests positive for CWD.

“The past couple of years it doesn’t matter if they’re bucks or does; if they’re 2½ years or older, half of them have CWD,” Purnell said. “At first it was mainly older bucks, but now we’re finding CWD in our 1½-year-old deer, so it’s getting worse. Why else would we suddenly find dead deer in our woods all the time?”

Reporting the Dead or Dying

The Purnells aren’t the only Wisconsinites reporting sick, dying or dead deer. The state’s Department of Natural Resources routinely responds to reports phoned in by hundreds of 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.

Those trends and numbers don’t surprise Bryan Richards, CWD project leader at the U.S. Geological Survey’s National Wildlife Health Center in Madison, Wisconsin. “That’s pretty typical in places where disease prevalence is high and it’s been there awhile,” Richards said. “A veterinarian who teaches at a Madison technical college has a small farm in the core CWD area. Her family and friends shot nine deer last fall (2019), and seven tested positive for CWD.”

Richards scoffs when skeptics say: “CWD didn’t kill those deer. Bullets did.” Or “CWD didn’t kill those deer. Starvation did.”

Richards’ response? “CWD is 100% fatal for deer that contract it, and it causes them to die sooner from everything else that kills deer. CWD makes deer more susceptible to illness, injuries, and starvation; and then kills them faster than they’d otherwise die from CWD itself. Pneumonia is especially common in CWD victims. Either way, no deer survives CWD.”

Richards said he understands why people are skeptical when CWD first appears. It usually spreads slowly, and seldom at a uniform speeds. CWD rates seemingly inched along in southwestern Wisconsin from 2002 through 2010, which is far different from what we’ve seen with COVID-19 in recent weeks. Even when biologists documented CWD’s slow increase, few people saw its impacts. As one biologist noted: “The deer woods aren’t hospitals. Deer don’t die beneath starched bed sheets in numbered rooms.”

The Purnells’ lands, for example, seemed safe. They’re roughly 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 widespread testing in Richland County from 2002 to 2006 — 5,745 tests, a 1,150 annual average — the Wisconsin DNR found only three cases: one in 2002 and two in 2005. Richland County covers 589 square miles (376,960 acres). The agency also found no CWD cases in 2007 and 2008.

Stealthy Infection

Seeing no great threat, lawmakers slashed the DNR’s budget in 2007. The timing couldn’t have been much worse. It’s now clear CWD had crept in and taken hold. Richland County hunters provided 660 samples in 2010, and the state veterinary lab confirmed 11 cases (1.6%). By 2018, the state tested 1,393 deer in the county, and found 187 (13%) cases. During the 2019 sampling year (April 1 to March 31), the county’s hunters volunteered 1,457 samples, and the state lab found 246 (17%) CWD cases.

Those numbers concern the Purnells, who have owned hunting land in Richland County since 1987. Mike Purnell thinks escalating infection rates explain what he and his brother see firsthand: More dead deer on the land, and a smaller herd with fewer old deer on the hoof. Purnell said deer numbers seemed to boom out of control five years ago as hunter numbers and hunting pressure declined, but he now sees fewer deer and a younger age structure.

“A lot of our neighbors don’t hunt or they shoot only big bucks, but we no longer see 5½- and 6½-year-old deer,” Purnell said. “This year I found three dead 2½-year-old 8-pointers. They don’t even see age 4 anymore. Our hunters shot 40 deer in 2018 but only 26 deer this past year. Our observations were down, too. It looks to me like Mother Nature is doing her thing, and controlling the herd for us.”

Richards doesn’t disagree. He thinks CWD also makes deer more susceptible to predation, bowhunters, gun-hunters, and collisions with motor vehicles.

“It only makes sense that deer would become more susceptible to cars, hunters and coyotes as prions destroy neurons and brain cells,” Richards said. “It’s hard to prove CWD is causing deer to be less wary or slower to respond to threats, but the research shows that once they get CWD, they’re more likely to be dead by the end of hunting season than are healthy deer.”

CWD Boosts Death Rates

Richards is referring to an ongoing Wisconsin DNR study that shows CWD-afflicted deer die at much higher rates than healthy deer in the same areas. Data in 2017 showed deer with CWD had a 75% annual mortality rate, while 2018 data put the mortality rate at 65%. Similar studies in Wyoming put the mortality rate at 68% in mule deer with CWD, and 60% in whitetails with CWD.

The Wisconsin research is led by DNR biologist Dan Storm, whose teams have collared and monitored over 1,000 deer, 57 bobcats and 69 coyotes in southwestern Wisconsin since 2017 to document what kills deer. Storm said they can’t yet conclude CWD makes deer more susceptible to hunters, but he supports what the Purnells report: plenty of dead deer in the woods.

“We call one spot Death Valley because we’ve found two of our collared deer along the little creek there, and you’ll find bones up and down the creek if you walk around down there,” Storm said. “But no one should be surprised if they don’t see lots of dead deer. They’re scavenged and scattered quickly. Whatever is left decomposes. Most people don’t see a lot of big bucks either. Deer usually don’t die or hang out where humans will likely see them.”