Big, sick, and rotting: Why tree size, damage, and decay are important to fisher reproductive habitat

Characterizing habitats associated with fisher den structures in the Southern Sierra Nevada, California using discrete return lidar

“…Resting and denning structures are considered to be the most important habitat elements required for maintenance of fisher populations (Lofroth et al, 2010;Weir et al, 2012). Fishers exhibit the greatest selection for natal dens and resting sites and the least for foraging locations (Kelly, 1977;Burnett, 1981;Arthur et al, 1989;Jones and Garton, 1994;Powell and Zielinski, 1994;Zielinski et al, 2006).…”

“…In the southern Sierra Nevada and at a large spatial scale, fishers selected den trees from a narrower range of biotic and abiotic conditions than habitats used for other activities; a combined analysis of 184 known den trees indicated that den structures were closely associated with densely forested stands including a moderately high proportion of hardwoods (Quercus kellogi), and at relatively lower elevations than predicted by a more general habitat model (Spencer et al, unpublished data). The actual den structures used by fishers in western North America are typically among the largest DBH trees and snags in the immediate area around the actual tree or snag (Lofroth et al, 2010;Weir et al, 2012). Biologists conducting ongoing research at four different areas within the West Coast Distinct Population Segment are all collecting detailed data on habitats around den trees within 12-m to 18-m radius circular plots centered on den trees.…”

Characterizing Habitat Elements and Their Distribution over Several Spatial Scales: The Case of the Fisher

“…This is similar to what Zhao [17] observed. Heterogeneous forests are also likely to contain greater numbers of hardwoods, which appear to be critical den structures-they were the greatest types of structures used for denning in this study area, and how den cavities form [30].…”

Assessing cumulative impacts of forest development on the abundance and distribution of furbearers.

“…The distribution of both species may be restricted by other factors such as elevation, overhead cover in recently logged areas, snow accumulation (Weir and Harestad 2003), or the availability of elemental habitat features like denning trees (Weir et al 2012). Competition with fisher may also limit marten in areas where they overlap (Carroll 2007).…”

“…Thus, during denning, female fishers are dependent on large, decaying trees, primarily deciduous or conifers such as Douglas fir and pine that have heart rot (Weir et al 2012). Managers must recognize the importance of maintaining or promoting den sites, but these features are not directly represented in largescale landscape models (McCann et al 2014), such as those presented in this work.…”