Selection of disturbed habitat by fishers (Martes pennanti) in the Sierra National Forest

Southern Sierra fisher (Martes pennanti) populations currently pose a management challenge for forest managers whose goals of forest fuels reduction often conflict with elements of fisher habitat conservation. My research draws upon Sierra National Forest management records and data collected by the Kings River Fisher Project to investigate the long-term effects of past management actions on fisher habitat. I used location data for 36 individual fishers (27 female, 9 male) to study second-order (home range and core-use area) and third-order habitat selection (resting and foraging sites) of national forest lands treated with management activities between 1992 and 2006. To better understand the possible drivers of fisher selection behavior I used light detection and ranging (LiDAR) data to compare treated and untreated forest structural characteristics. My findings indicate that fisher home ranges tend to include larger proportions of treated areas than are found on the landscape as a whole. In contrast, when selecting microsites within their home ranges, fishers tend to avoid using sites within 200 meters of a treated area. A possible explanation for the conflicting selection found here between home range and microsite selection is that the treated areas are generally small compared to a fisher's home range, and relatively dispersed on the landscape, allowing fishers to avoid the treated areas while still using the untreated areas surrounding them. Analyses of the LiDAR data indicate that forest areas that have been treated in the past continue to have reduced canopy cover and three-dimensional complexity, both primary indicators of fisher habitat quality, relative to untreated forest. These impacts do not appear to have rendered the habitat wholly unsuitable, however, and may be offset by increased fire resiliency. My findings suggest fishers may tolerate such fuels reduction treatments provided they focus on the reduction of surface and ladder fuels, and care is taken to maintain both canopy cover and sufficient abundance of forest structures, such as large diameter defective and standing dead trees, most likely to provide suitable rest and den sites.