White-tailed deer (Odocoileus virginianus) population dynamics in a multi-predator landscape
Duquette, Jared Fitzgerald
AdvisorBelant, Jerrold L.
Indices of white-tailed deer (Odocoileus virginianus) abundance in the western Upper Peninsula of Michigan suggested the population declined 40% from the previous 5 year mean following 2 consecutive severe winters in the mid-1990s and has not since increased in population size. I collected estimates and assessed biological and environmental covariates of survival and recruitment of fawns (< 1 year old) and age-specific reproductive and survival rates of adult females (> 1.6 years old) in the southwestern Upper Peninsula of Michigan from 2009–2011. Reproduction did not appear to regulate population growth, as 92 percent of females were pregnant. Annual survival of adult females was 70 percent across years, but poorer annual survival of fawns across years (44 percent) resulted in recruitment being the most influential vital rate to population growth, which increased10 percent from 2009 to 2010, but decreased 13 percent from 2010 to 2011. Variation in population growth emphasized that annual variation in fawn recruitment may have nullified increased growth over time. Most fawn mortalities occurred within 12 weeks of age, emphasizing this period greatly influenced annual survival rates of fawns, and especially population growth. Therefore, I suggest fawns should be considered the priority cohort for deer population management, including mitigation of factors which limit fawn recruitment. Winter severity effects on nutritional condition of adult females primarily influenced survival of adult females and fawns. However, adult female avoidance of interior lowland forests which had greater wolf (Canis lupus) use and commonly aging and over-browsed vegetation ostensibly reduced fawn recruitment through a lack of hiding vegetation and poorer forage. Also, by adult females raising fawns in habitats near roads, the predatory efficacy of coyotes (C. latrans) on adult females and fawns increased. Although predation was the leading cause of deer mortality, bottom-up effects of winter severity on nutritional condition and resource use appeared to be most influential to sustaining a lack of population increase. Hence, I suggest population growth could be improved through habitat management that increases landscape heterogeneity of early successional forests to enhance year-round browse to increase nutritional condition of adult females and hiding cover for fawns.