Chronic wasting disease (CWD) occurs in free-ranging white-tailed deer (Odocoileus virginianus) in the Lower Peninsula of Michigan, and in neighboring Wisconsin, where the disease is endemic. Before this study wildlife managers had not documented CWD in the Upper Peninsula (UP) of Michigan, though CWD was detected in two deer at two Wisconsin captive cervid facilities near the Michigan border. Officials now have identified the disease in facilities in Oneida County, Wisconsin (about 40 km from Iron County, Michigan), Oconto County, Wisconsin (about 50 km from Menominee County, Michigan), and Marinette County, Wisconsin (about 25 km from Dickinson County, Michigan). Additionally, two wild CWD positive deer were detected in Oneida and Lincoln Counties, Wisconsin, 68 and 74 km, respectively, from the Gogebic County, Michigan border. While it was not possible to predict if or when CWD would be found in the UP, preparations seemed prudent. On 18 October 2018 CWD was confirmed in Dickinson County’s Waucedah Township in a 4-year-old free-ranging female white-tailed deer that was shot in September 2018 on a crop damage permit about 6 km from the Michigan-Wisconsin border. A scientifically-based understanding of deer movements and estimates of population abundance is critical for developing management recommendations in response to CWD. Deer movements and abundance can influence the probability of disease occurrence, contact rates which can affect transmission rate, and geographic extent of an outbreak. Importantly, these data take time to gather and managers need this information to develop appropriate response plans.
Important deer space-use and movements to understand include seasonal home ranges, migration (especially important in the UP), dispersal, transient, and exploratory. Information on these movements would inform decisions on identification of CWD management zones. The current strategy is to establish a 16-km radius circle around the location of an infected cervid and include entire counties whose boundaries intersect this circle as part of the CWD management zone. Further, if results from local population surveys or other credible scientific data suggest that cervids from within the radius are likely to move beyond the management zone boundary, the boundary should be expanded accordingly. In the UP, deer can migrate seasonally up to 50 km (Van Deelen et al. 1998), with overall movements exceeding 80 km (Doepker et al. 2015). These migratory movements, as well as other movements (e.g., dispersal), are poorly understood and cannot be delineated by county boundaries.
Although some information exists on deer movements in the UP, most of this information was obtained using observations of deer with ear tags that does not provide the spatial and temporal resolution to inform management responses to a disease outbreak. Under the existing management response guidelines to CWD, large areas would likely be under surveillance and management that would not contain infected deer and large areas with potential for infected deer would not likely be within the prescribed surveillance zone, rendering management less effective. Our forthcoming models of white-tailed deer space-use, movements, and abundance are intended to be used to identify the spatial extent and relevant deer population for effective management of CWD. This will provide credible scientific evidence and allow managers to implement the CWD response plan more effectively, based on deer movement and population ecology.
After completing this research in the western UP, we intend to conduct parallel projects in the central and eastern UP to develop this strategy UP-wide. In addition to the primary objective of disease management, this research will inform the overall deer management program in the UP.
Objective 1. Quantify Timing and Extent of Deer Movements
Determine the frequency, distance, and timing of seasonal and extra-home range movements using data compiled from 50 radio-collared deer in each of 3 populations along the Michigan-Wisconsin border, plus 30 deer augmenting Phase 3 of the Predator-Prey study.
Objective 2. Estimate Deer Abundance and Composition
Estimate annual deer abundance and population composition using an unbaited camera array in each study population. During July–September of each year, we will place cameras on established deer trails based on early summer movements of adult female deer.
Objective 3. Management Outcomes
Develop spatially-explicit model outputs of probabilistic deer movements for each study population, incorporating deer density, to allow managers to apply appropriate sized management zones if CWD is discovered.
Four deer wintering complexes (DWC) in the western UP define the boundaries of the winter capture and collaring effort. Summer boundaries are defined by the movements of the collared deer. Additionally, following the discovery of CWD in Dickinson County in October 2018, we established a study area in southern Dickinson County to capture and collar deer defined by a 5 mile (8 kilometer) diameter area surrounding the index CWD case. Three DWCs are along the Michigan-Wisconsin border.
Little Girls Point DWC (LGP; 46.6037°, -90.3312°) is in the middle snowfall zone and receives an average of 76 days with >30 cm (>12 inches) of snow depth. Little Girls Point DWC covers about 65 km2 (16,082 acres) in Gogebic County along Lake Superior and immediately north of the Michigan-Wisconsin border. Land ownership within LGP is 45% private, 38% Commercial Forest, 11% Gogebic County School Forest, and 6% Ottawa National Forest.
Lake Gogebic DWC (LKG; 46.3999°, -89.4610°) is in the high snowfall zone and receives an average of 92 days with >30 cm (>12 inches) of snow depth. Lake Gogebic DWC covers about 691 km2 (170,764 acres) in portions of both Gogebic and Ontonagon Counties northwest of Marenisco. Land ownership within LKG is 55% Ottawa National Forest, 27% Commercial Forest, and 18% private.
West Iron County DWC (WIC; 46.0895°, -88.8024°) is within the middle snowfall zone and receives an average of 89 days with >30 cm (>12 inches) of snow depth. West Iron County DWC covers about 609 km2 (150,461 acres) in Iron County north and west of the city of Iron River. Land ownership within WIC is 43% Ottawa National Forest, 34% private, 19% Commercial Forest, and 4% State of Michigan.
East Middle Branch DWC (EMB; 46.5576°, -88.9358°) is in the high snowfall zone and receives an average of 91 days with >30 cm (>12 inches) of snow depth. East Middle Branch DWC covers about 295 km2 (73,000 acres) in portions of both Houghton and Ontonagon Counties north of Bruce Crossing. Land ownership within EMB is 61% Ottawa National Forest, 23% private, 12% Commercial Forest, and 4% State of Michigan.
Southern Dickinson County (DNC; 45.7357, -87.7484) is in the low snowfall zone and receives an average of fewer than 60 days with >30 cm (>12 inches) of snow depth. This region is also considered to be in the conditional range for white-tailed deer migration where due to lesser snow depths and snow cover deer do not need to migrate most years.
Locations of the 5 general study areas defined by deer wintering complexes (Little Girls Point, Lake Gogebic, West Iron County, and East Middle Branch) or the index case of an adult female deer that tested positive for chronic wasting disease in October 2018 (Southern Dickinson County), western Upper Peninsula of Michigan, USA. Inset shows location of study areas within the Great Lakes region of the USA.