By james art 
MADISON – The Wisconsin Department of Natural Resources recently presented the main results of the Southwest Wisconsin Chronic Wasting Disease (CWD) Deer and Carnivore Study to the Natural Resources Board (NRB). A recording of the NRB meeting, including this presentation, is available on the DNR YouTube channel.
The purpose of this study was to determine how CWD affects deer populations. This included assessing deer survival rates and how they were affected by CWD.
Fieldwork for this project took place in the northern Iowa towns of Dane and Grant. This area was chosen for study because it was the region where CWD was first detected in Wisconsin in 2002. and has maintained a high prevalence of CWD in the years since.
As part of this study, over 1,200 animals (adult deer, hens, coyotes, and bobcats) were captured, 766 GPS collars were placed on adult deer, and 323 radio tracking collars were placed on deer.
Results
The scientists analyzed data from a sample of adult white-tailed deer to assess differences in annual survival (the probability of surviving from one year to the next) between CWD-infected and uninfected deer.
These figures show that CWD significantly reduces the annual survival probability of both male and female white-tailed deer. Reduced female survival lowers population growth rates and, when sufficiently suppressed, can lead to population decline.
Specifically, the results of this study show that when female CWD prevalence rates exceed about 29%, deer populations are expected to begin to decline.
Consequences
The key takeaways from these results are:
● CWD significantly reduces deer survival rates and suppresses population growth.
● When CWD prevalence is high, deer populations likely decline.
● CWD will eventually affect deer populations elsewhere if it continues to spread and increase in prevalence.
If CWD continues to spread and its prevalence continues to increase, populations will likely face further declines. However, the exact extent of these declines will depend on local harvest and recruitment rates. It is important to note here that researchers do not expect CWD-affected deer herds to explode (completely eliminated in an area) because deer populations have a strong ability to increase reproduction when deer abundance is lower due to – little competition for food, space and other resources.
The public can learn more about these results by visiting the research results webpage.
I look ahead
It should be noted that the results presented here are the main findings of the southwest Wisconsin CWD and Predator study. While the scope of this study provides us with a rich data set from which to continue to learn about our deer herd and the impact of CWD, there are sure to be more results as the analysis continues. Additional findings will continue to be released to the public as completed.
To stay informed of these announcements and the results of additional analyzes on topics such as movement, habitat use, and predator survival rates, subscribe to the Field Notes newsletter.