Fishers (Pekania [Martes] pennanti) are a medium-sized mustelid endemic to North America. They are associated with old growth forests that contain ample cover, structure and large diameter trees.

Until recently it was assumed that fishers in the Rocky Mountains all descended from a non-native type from the Midwest and Canada reintroduced by foresters in the 1950s and 1960s. Our research showed the uniqueness and persistence of the Rocky Mountain fisher in north-central Idaho and west-central Montana. Some fisher in this region are likely descendants of a relic population of fishers that escaped harvests and trapping conducted in the early 20th century (Schwartz 2007). 

From 2007 to 2011, we led a multiagency survey (USDA Forest Service, Idaho Fish and Game, Montana Fish Wildlife and Parks, Coeur D’Alene Tribes, Potlatch Timber Company) to deploy nearly 5000 non-invasive genetic hair snares. Our effort detected fisher over 250 times. These data were key in building models to predict fishers’ current habitat at a broad scale, as well as potential future habitat under climate change scenarios (Olson et al. 2014). 

Our maps of predicted habitat are being used throughout the Northern Region of the Forest Service for planning purposes.  While our large scale surveys give us a general area of priority areas, we need a fine-scale understandings of fisher habitat selection to inform project work. 

RMRS is conducting field efforts in collaboration with the Northern Region of the Forest Service to explore mid-scale (i.e., stand level) habitat requirements for this species. For example, we discovered fishers need forests with ~50 percent of the composition being large trees (Schwartz et al. 2013). We also initiated studies with National Forest System partners to develop a fine-scale understanding of how fishers use specific elements in the forest.