Winter use of montane forests by porcupines in southwestern Alberta: preferences, density effects, and temporal changes

Abstract

The pattern of winter use of montane forest by porcupines (Erethizon dorsatum) during a 40-year period was examined on two areas in southwestern Alberta. Of the three available coniferous communities, porcupines fed in relatively more trees in pure stands of Douglas fir (Pseudotsuga menziesii) in leeward situations. Douglas fir, limber pine (Pinus flexilis), and hybrid spruce (Picea glauca × P. engelmannii) were used with equivalent frequency when found in the same community. The number of porcupines that used both areas peaked and declined in relation to the average ages of the forests. Trees in low density stands (< 11 trees/100 m2) were fed in during more years than those in denser stands and the use of dense stands was more frequent during years when porcupines were most abundant. Differences between the study areas in repeated feeding in leeward Douglas fir and in the relative proportions of trees used in low and high density stands are attributed to differences in the abundance of porcupines.