Predator-Prey:  The Study

Background

White-tailed deer (Odocoileus virginianus) survival is influenced by many factors including disease, predation, weather, and hunter harvest. In the Upper Peninsula of Michigan (UP), deer survival is strongly influenced by winter food supply and cover. Deer commonly rely on felled tree tops and subsequent growth of tree saplings for winter food. Additionally, deer seek landscapes with a high proportion of conifer trees, such as cedar and hemlock, to obtain shelter from snow and wind. The availability of these habitats effects over-winter survival in the UP.

Predators also play a role in deer survival, particularly fawn survival during spring and summer. Although some predators (such as coyotes) are able to take deer of any age, other predators (such as black bears) are able to catch fawns only during the first couple weeks of life. During winter, when deer are hampered by snow and in poor physical condition, predators are able to more readily kill deer. Understanding deer survival, and the factors that influence it throughout the year, is important for proper management of the deer herd.

White-tailed deer provide food, sport, income, and viewing opportunities to UP residents and visitors. In some areas, deer overabundance results in damage to farm crops, deer-vehicle accidents, and suppression of forest vegetation. For these reasons, it is important to monitor deer populations and understand the reasons why it increases or declines.

Historically, deer abundance in the UP has been affected by the intensity of timber harvesting and winter severity. Although these factors still exert a strong influence on deer populations, the role of predation is receiving more attention by both sportspersons and deer managers. Research is needed to better understand the impact of predation on deer, while also determining how predation is influenced by winter weather and deer habitat conditions.

Objectives

1. Estimate survival and cause-specific mortality of white-tailed deer fawns and does.
2. Estimate proportion of fawn mortality attributable to black bear (Ursus americanus), coyote (Canis latrans), bobcat (Lynx rufus), and wolf (C. spp.).
3. Estimate number and age of fawns killed by a bear, coyote, bobcat, or wolf during summer.
4. Provide updated information on white-tailed deer pregnancy and fecundity rates.
5. Estimate annual and seasonal resource use (e.g., habitat) and home range of white-tailed deer.
6. Estimate if familiarity of an area to each predator species affects the likelihood of fawn predation.
7. Assess if estimated composite bear, coyote, bobcat, and wolf use of an area influences fawn predation rates.
8. Describe association between fawn birth site habitat characteristics and black bear, coyote, bobcat, or wolf habitat use.
9. Estimate seasonal resource use (e.g., habitat, prey) and home range size of black bear, coyote, bobcat and wolf.

Study Area

Phase 1

This study was centered on a ~900 km² (~350 mi²) area within Deer Management Unit (DMU) 055 in Menominee County. The area is bordered on the east by the shoreline of Lake Michigan, on the north by US Highway 2, on the west by US Highway 41, and the south by the town of Stephenson. The core study area includes a mix of forested and agricultural lands and is where capture efforts occurred. This area was selected because of the relatively low snowfall and generally low winter severity. Deer in this area generally migrate only short distances or are non-migratory, facilitating comparisons with southern Michigan.

Phase 2

The second phase of this study spanned about 1,000 km² (386 mi²) within DMU 036 in Iron County. The general study area boundaries follow State Highway M-95 on the east, US Highway 41/28 on the north, US Highway 141 on the west, and State Highway M-69 on the south. The core study area, where most captures and population surveys occurred, is north of the Michigamme Reservoir and includes state forest, commercial forest association, and private lands. We selected this area because it occurs within the mid-snowfall range, receiving about 180 cm of snowfall annually (about 53 cm more snowfall annually than the phase 1 study area near Escanaba). Deer in this area migrate longer distances and exhibit yarding behavior during most winters as compared to Escanaba where deer migrate only short distances or are non-migratory and yard less frequently.

Phase 3

The third phase of this study spans about 1,550 km² (598 mi²) within DMU 031 in Baraga, Houghton, and Ontonagon Counties. The general study area boundaries follow US Highway 41/141 on the east, State Highway M-38 on the north, US Highway 45 and State Highway M-26 on the west, and State Highway M-28 on the south. Dominant land covers are deciduous (35%), evergreen (23%), and mixed (21%) forests. Road density is low across the study area at 0.62 km/km² but higher densities occur around small towns on the periphery. The core study area, where we are conducting most captures and population surveys, is centered on National Forest Rd 16 and almost exclusively within the Ottawa National Forest. We selected this study area because it occurs within the high-snowfall range, receiving over 250 cm of snowfall annually (about 70 cm more snowfall annually than the Phase 2 study area near Crystal Falls).