A HIERARCHICAL MODELLING APPROACH TO PREDICT THE DISTRIBUTION, DENSITY, AND HABITAT RELATIONSHIPS OF FISHERS IN WASHINGTON, OREGON, AND CALIFORNIA

Sean M Matthews; Oregon State University; sean.matthews@oregonstate.edu; Marie E. Martin, Eric L. McGregor, Erika L. Anderson, Christine Jordan, Stephanie Eyes, Frank Weaver

Fishers (Pekania pennanti) are a medium-sized carnivore of conservation concern in portions of the western United States. Fishers in the southern Sierra Nevada of California are federally endangered and other populations in the western United States have been evaluated for federal listing. Small and isolated populations are the most immediate and challenging threat to fisher persistence in Washington, Oregon and California. Species distribution, habitat associations, and population size are critical information needs for species recovery. Distribution patterns and habitat associations have been evaluated using presence-only and expert opinion models. These models, however, frequently fail to meet assumptions, increasing calls for analyses in detection-non detection frameworks. We modeled the distribution, abundance, and habitat relationships of fisher across Washington, Oregon, and California. We developed a hierarchical model of detection-non detection data using occupancy and integrated modeling. We found that the use of bait and surveying in the winter had positive influence on the detection of fishers. We also found that canopy cover, the standard deviation of canopy cover, and stand age influenced patterns in fisher abundance. Our results will be a useful decision-support tool to promote species recovery in the face of stochastic events and a changing climate.

Ecology and Conservation of Mammals (Small Mammals)