Evaluation of Deer Population Parameter Estimates and Implications for CWD

Principle Investigators: Sonja Christensen, MSU Dept. Of Fisheries & Wildlife, Steven Gurney, MSU Dept. of Fisheries and Wildlife

Deer hunters account for the largest portion of the hunting public in the United States. This distinction is important because deer-hunting related expenditures and license sales generate many conservation dollars—not only for the benefit of game species, but for non-game too. Therefore, wildlife managers must assure the health of deer populations to sustain the overall economic well-being of wildlife conservation. However, Michigan has an emerging problem on their hands—chronic wasting disease (CWD). Chronic wasting disease affects species in the deer family, and once a deer is infected, there is no recovery—it is always fatal. Deer can become infected with CWD through animal-to-animal contact or through contaminants in the environment (e.g., feces). Since first identified in Michigan’s free-ranging deer in 2015, CWD has been detected in 3 primary areas (southwest Upper Peninsula, and south-central and southeast Lower Peninsula) across the state—with most positive animals detected in a designated 5-county Core CWD Area (Ionia, Kent, Mecosta, Montcalm, and Newaygo counties). As CWD continues to be detected in new areas, it is becoming more relevant every day. From what we learned from other states that have experienced CWD, the disease spreads slowly through a population. We also know that mature bucks are more likely to be infected than any other sex or age deer. An approach to try to reduce transmission and maintain low levels of prevalence in a population is to target deer that are more likely to be infected, and to also reduce deer abundance. It is generally believed that deer hunting regulations that limit hunter harvest to specific sex and age deer can achieve this, but this is untested in free-ranging deer populations. Mandatory antler point restrictions, or APRs, is a common deer harvest regulation meant to target mature bucks based on antler size. Because APRs reduce the number of bucks in a population available for hunters to harvest (e.g., younger bucks with smaller antlers are protected) it is also believed that hunters will harvest more does—and removing more does from a population may reduce deer abundance. However, there is a limited understanding how APRs change populations and how those changes interact with CWD. So, the APR Study was developed to address the first research question, “how do APRs change relative abundance and sex and age composition of deer populations?” 

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