The Midwest's white-tailed deer are iconic. Whether it’s hunting season or spotting them in the wild, they’re part of what makes Wisconsin and the Tri-States special. But deer face some big challenges, and the Wisconsin Department of Natural Resources wanted answers. That’s why they launched the Southwest Wisconsin CWD, Deer, and Predator Study, one of the most ambitious wildlife research projects in the state’s history.

Credit: Canva
Credit: Canva
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After years of tracking deer and predators (coyotes and bobcats), they’ve uncovered important insights into how diseases like chronic wasting disease (CWD) and local predators are shaping the future of our deer populations.

Credit: Wisconsin DNR Summary of the deer, bobcats and coyotes captured for the study from 2017-2020.
Credit: Wisconsin DNR
Summary of the deer, bobcats and coyotes captured for the study from 2017-2020.
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First, let’s talk about CWD. It’s a fatal disease that impacts deer, elk, and moose, and it’s caused by prions—basically, rogue proteins that mess up the brain. A sick deer might look skinny, confused, or uncoordinated, and the disease is always fatal. Worse, prions can stick around in the environment for years, contaminating soil and plants. This makes CWD extremely hard to manage.

The study’s big question was: how is Chronic Wasting Disease really affecting deer in Southwest Wisconsin? The results are eye-opening. Deer infected with CWD are four times more likely to die than healthy deer, and the disease is already cutting into overall deer survival rates. In areas with a lot of CWD, this could mean population declines over time. What’s more, the disease is spreading steadily, with prions showing up in the environment where deer live and feed.

Credit: Wisconsin DNR The graph highlights the connection between CWD prevalence and deer population growth. The y-axis represents population growth rate, which measures whether a population is increasing (above 1) or decreasing (below 1). The x-axis shows the percentage of adult deer infected with CWD, ranging from none (0.0) to 60% (0.6). The dashed line marks population equilibrium, where growth balances out. If the solid line is above the dashed line, the population is growing; if below, it’s shrinking. Findings from this study reveal that when CWD prevalence in adult females exceeds roughly 29%—the point where the lines meet—deer populations begin to decline.
Credit: Wisconsin DNR
The graph highlights the connection between CWD prevalence and deer population growth. The y-axis represents population growth rate, which measures whether a population is increasing (above 1) or decreasing (below 1). The x-axis shows the percentage of adult deer infected with CWD, ranging from none (0.0) to 60% (0.6). The dashed line marks population equilibrium, where growth balances out. If the solid line is above the dashed line, the population is growing; if below, it’s shrinking. Findings from this study reveal that when CWD prevalence in adult females exceeds roughly 29%—the point where the lines meet—deer populations begin to decline.
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But here’s something surprising: predators like coyotes and bobcats aren’t a major contributor to the downward spiral in whitetail numbers. Sure, they do kill some deer, especially fawns, but their overall impact is pretty small. In fact, CWD and hunting were found to be much bigger factors in deer mortality. So, while natural predators play a role in the ecosystem, managing them won’t solve the bigger issues deer are facing.

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Credit: Canva
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Speaking of hunting, since it's a major cause of deer mortality, it is important to understand that hunters play a critical role in controlling CWD’s spread. By harvesting infected deer and helping with testing efforts, the study highlights hunting is not just for fun or the sake of tradition, but for conservation and disease management.

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So, what does this mean for the future? First and foremost, we need to focus on tackling CWD. This could mean more widespread testing, research into vaccines or treatments, and finding new ways to slow its spread. It also means continuing to educate hunters and the public about the disease and how we can all help.

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Credit: Canva
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Speaking of which, how can conservationists and hunters help stop the spread of CWD? Hunters should always test harvested deer for the disease, properly dispose of carcasses in approved facilities to avoid contaminating the environment, and avoid baiting or feeding practices that congregate deer and increase disease transmission. Meanwhile, conservationists continue to advocate for habitat management strategies that promote healthy deer populations and work to educate the public about CWD’s impact. Both groups can support ongoing research and collaborate with agencies like the Wisconsin DNR to monitor and contain the disease.

The study also reminds us that keeping ecosystems healthy is about balance. While predators aren’t the main issue for deer, maintaining habitat and a healthy predator-prey dynamic is still important for overall wildlife management. And, of course, hunters will always have a key role to play in Wisconsin’s conservation efforts.

At the end of the day, this research is a wake-up call about how complex wildlife management can be. Chronic wasting disease is a serious challenge, but with smart strategies, cooperation, and continued research, there’s hope for Wisconsin’s deer. Whether you’re a hunter, conservationist, or just love seeing deer out in the wild, this study shows that we all have a part to play in protecting these incredible animals for generations to come.

It’s important to note that these results are just the primary findings of the study. While they offer a wealth of data that will help us better understand our local deer populations and the impact of CWD, it’s just the beginning. As researchers continue to analyze the data, more findings will emerge, providing deeper insights. The Wisconsin DNR will continue to share additional results with the public as they become available.

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