What does a CWD Study in Wisconsin have to do with mule deer across the West?

A five-year study on CWD in Wisconsin is finally ready for publication and release to the world. Results from the Wisconsin DNR’s largest deer and chronic wasting disease (CWD) study ever undertaken show that the disease substantially reduces deer survival rates and suppresses deer population growth.

Dr. Dan Storm, a DNR ungulate research scientist, reported the results of the seven-year study in southwest Wisconsin to the Natural Resources Board on Jan. 22.

“People should expect fewer deer in areas of high CWD prevalence,” Storm said. “Deer are not going to go extinct, but there will be fewer of them.”

We spoke with Dr. Daniel of the Wisconsin Department of Natural Resources about CWD, his study, and what the broader implications of CWD across the West could look like. Dr. Storm and his team collared and tracked over 1,000 whitetail deer (766 adults and 323 fawns) over a 5-year period with CWD, and a post-mortem study was done on each deer within 24 hours after the collar sent a mortality signal.

The key takeaways from these results are:

Of the 1,000+ deer collared for this study, 61% have died. 26% had a collar failure of some kind, and 13% are still alive and transmitting movement data to the research team. Of all deer necropsied, 42% were CWD-positive.

CWD-positive deer were much more likely to be emaciated (severely starved) and were more likely to have noticeable ectoparasites (such as lice and ticks) on their bodies. Pinkerton classified over 75% of CWD-positive deer as having poor nutritional conditions.

CWD substantially reduces deer survival rates and suppresses population growth.
Where CWD prevalence is high, deer populations are likely declining.
If CWD continues to spread, it will eventually impact deer populations elsewhere.

“While our research shows the general relationship between CWD prevalence and deer population growth, varying local conditions, such as harvest and recruitment rates, will play a role in the deer population trend that is ultimately observed. It is important to note that researchers do not expect CWD-affected deer herds to become extirpated (locally extinct).” – Dr. Storm.

For more on this study, please visit: https://dnr.wisconsin.gov/topic/Research/articles/april2022#articleOne

What does this mean for mule deer?

This study is a repeatable benchmark for agencies across the West to use as guidelines and a model to study CWD in mule deer and elk. Furthermore, it highlights the extreme mortality rate among animals that have contracted CWD. In fact, in Wisconsin, CWD was the second highest cause of mortality in the region behind coyotes.

Will CWD be the reason that mule deer go extinct? No, according to the study, it will severely reduce their numbers. It will allow issues like increased predation, other diseases, and tick investigations to run through the depleted herd. There is also an interesting note on how the human harvest of those has a more significant role in combating CWD than previously thought. This doesn’t mean you should go out and shoot every mule deer you find in a CWD area, but it does mean more research needs to be done on CWD in western states.

Note on Human Health Implications

Another result of the study is the contraction of humans and CWD. To date, there have been no cases of CWD infection in humans. Multiple studies conclude that the species barrier between deer and humans is strong. There are, however, some studies that suggest CWD could pose a risk to non-human primates. Squirrel monkeys are found to be susceptible to oral CWD infection. Multiple studies indicate that a new strain emergent could alter the likelihood of transmission to non-species.

In case you didn’t already have a dog in this fight, the implication is that in our lifetime, CWD or a CWD mutation has a chance of being able to infect humans.

Good Luck

As always, good luck this winter, and remember to send any success pictures or stories from the field to [email protected]. You could be featured on our website or in our magazine. If this article or any of our articles have helped you become a better hunter or conservation steward, consider becoming a member of the Mule Deer Foundation, the Blacktail Deer Foundation, or both. Click here to join: https://muledeer.org/product-category/membership/ or https://www.blacktaildeer.org/

Trevor J Hubbs @TrevorHubbs on Instagram

Trevor is the Communications Manager for the Mule Deer Foundation and Blacktail Deer Foundation. He grew up hunting and fishing the eastern edge of the Ozark Mountains for quail, ducks, and bucks. Trevor is also a contributor for “Fur, Fish, and Game”, “Lethal Minds Journal”, “Strung Magazine”, “Fly Fisherman”, and “Shooting Sportsman” among others.