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 high priority 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.

This 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 (2017-2020) 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 1,400 animals were collared and released to live out their lives. The second and current phase of the project is focused on data analysis. Data is still pouring in from the radio collars of the individuals who are still alive, but parts of the model can be analyzed and incrementally assembled. All of these smaller analyses will fit together to form the main model of the project, the Integrated Population Model (IPM).

Objectives

The overall objective of this research is to gain a comprehensive understanding of deer population dynamics in the CWD-endemic region of southwestern Wisconsin. This study incorporates lessons learned from the recently completed deer mortality study.

The specific objectives of this study within the CWD-endemic area are to:

1. Estimate weekly survival and the temporal changes in competing sources of mortality, due to CWD, predators and hunting, in the CWD-endemic area and relate them to an individual’s CWD status, overall CWD prevalence in the study area, genetic makeup, age, sex class and habitat variables.
    
2. Quantify deer metrics that affect survival and reproduction; CWD prevalence, deer pregnancy rate and litter size, nutritional condition of deer, deer recruitment, occupancy and abundance indices of deer and predators and timing of spring green-up and phenological variables that affect deer condition.
    
3. Estimate the abundance and distribution of coyotes and bobcats to gain a more definitive understanding of the relationship between predator numbers and deer mortality rates across different deer age classes. In addition, researchers will calculate the number of deer killed from individual bobcats and coyotes.
    
4. Quantify forage availability and quality to more directly understand the relationship between forage, nutritional condition, starvation and pregnancy rates in deer.

Ultimately, the project’s main objective is to combine what we learned from these specific objectives to produce a robust, Integrated Population Model (IPM) that combines data on survival, reproduction, recruitment, age-at-harvest and trail camera data. The IPM needs to be capable of estimating the current deer population size, reconstructing the historic dynamics of deer populations in the CWD-endemic area and simulating future deer populations under alternative harvest scenarios and projected changes in CWD prevalence. Great care is going into the assembly and testing of the model. Additional analyses are planned that are not part of the IPM but are relevant to hunters, managers and conservationists. 

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. 

Study Area

The fieldwork takes 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.