Habitat ecology of fishers in western North America

Call Number:

Keywords:

Abstract:

The authors of this chapter present a synthesis of the habitat associations of fishers (Martes pennanti) in western North America based on information produced since 1994. Contrary to limited results from previous studies, evidence from contemporary research indicates that fishers in western North America are not dependent on old-growth conifer forests for survival. Rather, fishers were associated with complex vertical (e.g., large trees and snags) and horizontal (e.g., large logs and dense canopy) structure characteristic of late-seral forests. Fisher distribution (f rst-order selection) was associated consistently with expanses of low- to mid-elevation mixed-conifer or conifer-hardwood forests with relatively dense canopies. Fisher home ranges (second-order selection) were characterized by a mosaic of available forest types and seral stages, including relatively high proportions of mid- to late-seral conditions, but low proportions of open or nonforested environments. Patterns of habitat use or selection by fishers were strongest at finer spatial scales (third- and fourth-order selection) and demonstrated that the fisher is a structure-dependent species in western North America. Female fishers are obligate cavity users for reproduction; tree cavities appeared to provide secure environments for kits by regulating temperature extremes and limiting access by predators. Compared with availability, fishers consistently selected large live trees, snags, and logs for resting that resulted from long-term forest growth and decay processes. Thermoregulation is more important to fishers than was recognized previously and appeared to influence selection of rest structures and sites. Tree pathogens (e.g., heart-rot fungi, mistletoe) are essential for creating the microstructures used for reproduction (cavities) and resting (e.g., cavities, branch platforms), and represent important components of fisher habitat throughout the species’ range in western North America. Our understanding of fisher habitat ecology has improved substantially since 1994. Nevertheless, focused investigations of the mechanisms that may influence habitat selection by fishers at multiple spatial scales (especially at the home range scale), and correlating use or selection of environments to measures of individual fitness, are needed to better understand fisher habitat quality and improve the conservation and management of fisher populations in western North America.

Notes:

ELECTRONIC FILE - Zoology