American marten survival and movement in the presence of fishers
Conservation of predators that have been reintroduced to their native range can be improved through studies of their demographic rates, resource use, and activity patterns. I studied American martens (Martes americana ) and fishers (Martes pennanti) in northern Wisconsin, USA, where they were reintroduced following extirpation in the 1930s. Fisher populations have increased since reintroduction, but marten populations have not increased. In my first chapter, I studied marten survival. Results indicate that low survival of adult martens has not limited their reestablishment in Wisconsin and that fisher and raptor kills had only a moderate impact on adult marten survival. In my second chapter, I studied marten and fisher resource use within their home ranges during winter. Areas dominated by eastern hemlock (Tsuga canadensis) and northern white cedar (Thuja occidentalis) contained more use sites (i.e., rest and kill sites) than was expected. Martens also selected the hemlock-cedar cover type along their movement paths, and hemlock-cedar is where they moved most sinuously and oriented least efficiently toward rest sites. Martens may have concentrated their activities in hemlock-cedar because they found rest sites and small mammal prey there, and small mammals sustain their energetic demands. Despite a greater number of use sites in hemlock-cedar, fisher path sinuosity, orientation efficiency, and selection metrics did not vary by cover type. Fishers rested in hemlock-cedar but may require larger prey typically found in other cover types to sustain their energetic demands, such as snowshoe hares ( Lepus americanus). In my third chapter, I studied patterns of marten and fisher activity during winter. Results from activity monitoring are consistent with the hypothesis that marten and fisher activity is motivated by prey availability. The poor predictive ability of my final models indicated that activity levels are motivated by multiple factors and/or factors other than environmental conditions and gender. In my last chapter, I studied marten use of cover types at the scale of the home range and landscape. Resident martens selected evergreen forest at the home range scale during winter. Simulation results indicated that martens dispersing from release sites supplemented use of evergreen with adjacent cover types found within 100 m. Evergreen cover types may provide cover from raptors and harsh winter conditions and 100 m may represent a distance within which martens can find cover quickly. Additional simulation runs may elucidate this pattern. Collectively, this body of research is useful for conservation of martens and fishers. My results indicate that survival of adult martens has not limited their reintroduction and that other demographic rates such as juvenile survival or fecundity require investigation. Hemlock-cedar is important for martens in northern Wisconsin due structure found within it that provides rest sites and prey availability. It is also important for fishers because it provides rest sites. The context within which hemlock-cedar is found is important because both species used rest sites and killed prey in adjacent cover types. They may have constructed their home ranges around hemlock-cedar and supplemented its use with other cover types that contained rest sites and prey.^
Patrick A. Zollner, Purdue University.
Agriculture, Wildlife Conservation|Agriculture, Wildlife Management|Biology, Conservation