Effects of Scale on Habitat Selection and Foraging Behavior of Fishers in Winter

Abstract

Several researchers reported that fishers ( Martes pennanti ) select lowland-conifer habitats, where snowshoe hares ( Lepus americanus ) are abundant, for foraging and resting and therefore, avoid open, upland-hardwood habitats. In the Ottawa National Forest, Upper Peninsula, Michigan, in the 1970s, porcupines ( Erethizon dorsatum ) occurred in open, upland-hardwood habitat that provided fishers with more than on-half of their energy requirements. If fishers select habitat on the basis of location of important prey, they should hunt disproportionately in hardwood habitat. Fishers, however, appeared to recall locations of porcupine dens in winter and traveled directly to dens, thereby minimizing distance traveled in habitat of porcupines. I hypothesized that fishers would avoid upland-hardwood habitat, despite availability of porcupines, because foraging for porcupines is efficient. Tracks of fishers were followed and mapped. Distribution of habitats available near tracks and available in the study area were quantified using random transects on maps of habitat types. Fishers selected habitats on at least two different scales. On the coarser scale, fishers foraged in areas with greater availability of pine habitat and lowland conifers and less upland hardwoods than was available over the entire study area. On a finer scale, within the vicinity where fishers foraged, they selected lowland-conifer forest and avoided open areas, northern-hardwood, aspen-birch and hemlock forests. Fishers selected dense, lowland forests and avoided northern hardwoods for rest sites; selection of habitats for rest sites was stronger than for travel, making this a possible third scale of selection.