About the SW CWD Study

Project Intention and Overview

The Southwest Wisconsin CWD, Deer and Predator (SW CWD) Study is the largest deer and chronic wasting disease (CWD) study the DNR has ever undertaken. The purpose of this study is to understand the factors that influence deer and deer populations and combine them into a single model. By including all the major factors of deer survival, researchers can get a more definitive view of how all these factors, namely CWD, impact Wisconsin's deer populations. 

Studies in the western USA have found that CWD negatively impacts elk and mule deer survival and population size, but no field research has documented the impact of CWD on white-tailed deer survival or population growth in Wisconsin. Furthermore, there is not any ongoing work in the Midwest that specifically addresses the direct impact of CWD on deer survival. However, CWD continues to be a concern among Wisconsin deer hunters, county deer advisory councils (CDACs) and wildlife managers. There is particular interest among these groups to understand the impact of CWD and how it interacts with other important factors of deer population size and health, such as predation and recruitment.

The SW CWD Study was set up to build a singular model that can discover CWD's impact on Wisconsin's deer. From the beginning, the project was designed to be the largest project of its kind, both in terms of the number of individuals included in the study, as well as the number of factors included in the model.

The first few years of the project (2016-2020) comprised the first phase of the project, where staff were capturing and collaring animals. This phase set up the project's data collection infrastructure. Over 1,200 animals were collared and released to live out their lives. The second and current phase of the project is focused on analyzing the plethora of data gathered during the first phase. The massive amount of data gathered by the SW CWD Study will not only help several other study objectives but also the main goal of the project: building a comprehensive Integrated Population Model (IPM). The IPM will help us better understand Wisconsin's deer population and allow future management decisions to comprehensively factor in how CWD affects deer survival in concert with predation, hunting, and other factors that determine deer population changes. 

 Study Area

The fieldwork took place in southwest Wisconsin, encompassing the area with some of the highest observed CWD prevalence in the state and the place where CWD was initially discovered in Wisconsin.

Objectives

Overall, this research seeks to gain a comprehensive understanding of deer population dynamics in the CWD-endemic region of southwestern Wisconsin. This study incorporates lessons learned from prior deer mortality research.

The primary objectives of the SW CWD Study are to:

1. Estimate survival and competing sources of mortality (for example, starvation, disease, predation and hunting) in the CWD-endemic area and relate them to an individual's status, age and sex. 

   1. Cause of death, pathology, and chronic wasting disease status of white-tailed deer, Gilbertson, et al.   

   2. April 2022 Field Notes: Adult Deer Necropsy and Fawn Survival Analyses

2. Construct an Integrated Population Model (IPM) to determine the deer population response to changes in CWD prevalence. 

The project will combine what we learned from Objective 1 to produce Objective 2, a robust Integrated Population Model (IPM). This model needs to be capable of estimating the current deer population size and simulating future deer populations under alternative harvest scenarios and projected changes in CWD prevalence. 

Additional Analyses

Additional analyses were planned that are not part of the IPM but are relevant to hunters, conservationists, wildlife managers and land managers.  Thanks to the immense fieldwork and data collection from over 1,200 animals for this study, several other study objectives on deer, bobcats, and coyotes were able to be completed in conjunction with the SW CWD Study. The findings from these studies have contributed to the overall understanding of how the many factors in deer survival and movement interact in Wisconsin. 

1. Determine how CWD status influences deer movement, activity, and habitat selection.  
2. Investigate aspects of juvenile deer dispersal rates, distances, and directions; how the landscape facilitates, hinders, and directs dispersal.  
   1. Agricultural land use shapes deer dispersal, Gilbertson, et al. 
   2. November 2022 Field Notes: Juvenile Deer Dispersal 
3. Quantify buck movement, range area and activity during the rut.  
   1. December 2023 Field Notes: Buck Movement Ecology During Rut 
4. Examine seasonal sex- and age-specific movement, activity, and habitat selection patterns of deer.  
5. Estimate the survival and cause-specific mortality of coyotes and bobcats.  
   1. Survival and cause-specific mortality of coyotes in Wisconsin, Margenau, et al.  
   2. November 2021 Field Notes: Results from Coyote Survival and Cause-specific Mortality Study  
6. Document home range size and habitat use of bobcats and coyotes. 

Collaborators

We partnered with the National Wildlife Health Center, the Wisconsin Cooperative Wildlife Research Unit, and the Montana Cooperative Wildlife Research Unit. We would also like to thank everyone who participated, whether as staff, volunteers or landowners who granted permission to trap on their land. 

Project Updates

The research team provides updates on fieldwork, research findings, and the project through the project newsletter, Field Notes. DNR researchers and collaborators working on the project have also recently started releasing their findings through peer-reviewed scholarly publications, which can be found in Deer & CWD Scientific Publications.