Vegetation Determines Where Fishers Winter
Habitat characteristics such as tree age, crown closure and fallen logs, point to how well-suited a forest is for fishers in winter. Data on these and other features from the British Columbia's Vegetation Resources Inventory can reliably map where on the landscape fishers are most likely to be during winter.
Terrain in the Sub-boreal Spruce and Interior Cedar Hemlock biogeoclimatic zones of central BC was mapped based on the inventory as to its quality for fishers. Subsequently, 84 percent of fisher tracks were found during surveys at excellent and high quality sites. A few simple criteria distinguish the better quality habitat for this species at risk.
Of the fisher tracks encountered in snow, 94 percent were in coniferous forests, with 83 percent concentrated in mature or older stands of large trees. Fishers especially frequent forests over 80 years old with snags and fallen trees, and with a 30-60 percent canopy closure. They also prefer stands where trees larger than 21 cm diameter at breast height total over 20 m² per ha in basal area.
These older, complex forests benefit fishers by intercepting snow and offering resting sites. In addition, the habitat accommodates prey such as snowshoe hares, red squirrels and southern red-backed voles. Even though large areas of shrub cover also attract fisher prey, shrubs have no noticeable influence on where fishers reside.
Gilbert Proulx. 2006. Using forest inventory data to predict winter habitat use by fisher Martes pennanti in British Columbia, Canada. Acta Theriologica. 51(3): 275-282.