Land-use patterns and population characteristics of white-tailed deer in an agro-forest ecosystem in south-central Michigan

Assessments of demographics and space use are important for habitat and harvest management of white-tailed deer (Odocoileus virginianus). These population characteristics often vary across a landscape, and by age (e.g., fawn, yearling, adult) and sex class. Knowledge of demographics and space use of young fawns is particularly limited, despite the potential for recruitment having a relatively large influence on deer population dynamics. My objectives were to describe age-specific survival, cause-specific mortality, and space use in an agro-forest ecosystem undergoing increasing urbanization (i.e., increasing housing developments, increasing human population) in south central Michigan. I captured, radiomarked, and monitored 66 deer during winter and 34 neonates during spring 2004 2006. Annual survival varied by age class (fawn = 0.51, yearling = 0.94, adult = 0.56), and annually based sources of mortality were primarily vehicle collisions (fawns) and hunter-harvest (adults). Two- and 6-month post-capture survival estimates of neonates were 81% and 67%, respectively, and canids caused most mortalities during both time periods. Yearlings had larger seasonal home ranges (agricultural growing season: x¯ = 201.8 ha +/- 91.1 SE; non-growing season: x¯ = 156.9 ha +/- 28.2 SE) than either fawns (60.2 ha +/- 14.1; 116.3 ha +/- 20.6) or adults (77.5 ha +/- 9.6; 140.4 ha +/- 23.4). Home ranges for fawns 0-2 months old averaged 40.9 ha (range = 2.7-166.8), with conifers and lowland deciduous forests selected in proportions higher than available on the study area. Adult female deer had relatively small home ranges compared to deer in other Michigan studies indicating that their habitat components were readily available. Additionally, this sex-age class is of primary interest to managers desiring to reduce high deer numbers. To describe cover selection of adult female white-tailed deer (n = 20), I used a multi-scale approach by varying definitions of cover use and availability. The number of cover types assigned as selected decreased from coarse (landscape) to fine (within home range) scales. Two cover types (conifers, upland deciduous forests) were consistently ranked as the most important regardless of scale. I used the concept of usable space (i.e., "ideal" permanent cover situations) to describe a potentially more accurate biological representation (compared to traditional home-range estimators) of space use by adult female white-tailed deer. Fixed-kernel home-range estimates might misrepresent space use by including cover types with no location estimates (i.e., no evidence of use). Usable space estimates (ha) were approximately 75% that of kernel home ranges, and were dominated (∼87% of area) by upland deciduous forest, lowland shrub, agriculture, and coniferous cover types. Under the assumption that deer densities are positively correlated with the amount of usable space, several cover conversion scenarios (i.e., habitat manipulation) would theoretically change deer abundance on an area of interest by changing the amount of usable space. Knowledge of age-specific deer demographics and addressing deer-habitat management issues through a multi-scale perspective and a usable-space approach are both relatively recent but seemingly useful concepts that also have relevance to population ecology of deer and other wildlife species.