THE SPATIAL ECOLOGY OF GRAY WOLVES IN THE UPPER PENINSULA OF MICHIGAN, 1994–2013

• Main Author: O'Neil, Shawn
• Format: Text
• Language: unknown
• Published: Digital Commons @ Michigan Tech 2017
• Subjects: Canis lupus; recolonization; survival; density dependence; ideal-free distribution; habitat selection; Bioinformatics; Population Biology; Terrestrial and Aquatic Ecology; gray wolf
• Online Access: https://digitalcommons.mtu.edu/etdr/451; https://digitalcommons.mtu.edu/cgi/viewcontent.cgi?article=1502&context=etdr

All natural processes are dynamic in space and time. Establishing the links between spatiotemporal patterns and ecological processes is critical for improving our understanding of natural systems. Empirical data representing wildlife populations is accumulating and increasingly involves spatiotemporal components. Wildlife monitoring programs for threatened, endangered, or other species of interest often involve radio-tracking of a sample of individual animals combined with census data. Such data are valuable both for conservation and management of populations and for testing ecological theories about species distribution and what influences patterns over time. We used 20 years of radio telemetry and snow tracking data to evaluate spatiotemporal patterns in gray wolf (Canis lupus) distribution, habitat selection, survival, and mortality in the Upper Peninsula (UP) of Michigan, USA. Wolves recolonized the study area during the early 1990s and exceeded a population size of 600 individuals before the end of the study. In addition, wolves were on the Endangered Species List during the majority of the study. This work therefore explores the spatial ecology of endangered wolves during a period of population recovery. We analyzed winter prey distributions of wolves, evaluated theoretical and modern empirically-driven models of density dependent habitat selection, estimated annual survival, and explored cause-specific mortality. Our methods included isodar analysis, spatiotemporal generalized linear mixed models of habitat selection, proportional hazards models with time-dependent spatial covariates, and competing risks analysis. Winter prey distributions exhibited a habitat functional response depending on winter snow conditions, resulting in a geographic prey limitation that affected wolf territory occupancy within the study area. Density-dependence in habitat selection revealed that wolf selection patterns were more consistent with an ideal-preemptive habitat distribution, as opposed to the ideal-free distribution. Density-dependent habitat selection patterns revealed decreasing selection for prey availability at greater wolf densities, while selection for anthropogenic features such as road density increased. However, selection across time exhibited occupancy-dependence as opposed to density-dependence. Wolf annual survival was ~ 75% and was influenced by sex, age, transient status, agriculture, habitat edge, wolf density, and Julian day, as well as several individual factors. Survival declined as wolf density increased, resulting in a shifting mosaic of wolf survival. Human-caused mortality increased with wolf density and was the primary mortality source of UP wolves, comprising ~ 17% annually. Much of human-caused mortality was attributed to illegal killing. Human-caused mortality was partially compensated for by natural mortality, and negative impacts on population growth rate were most evident when human-caused and natural mortality were both high. The spatial ecology of wolves in this study describes patterns associated with a growing and shifting population. Density-dependent effects population dynamics occurred with expanding wolf range, where later colonizers were forced to utilize habitats closer to human populations. Theoretical tests revealed potential for source-sink population dynamics. Evidence suggested the population had stabilized by the end of the study, and that suitable habitat was saturated. Future conservation of the population will likely depend on preservation of high quality source habitats and managing human conflicts associated with high wolf density areas occurring near population centers.