In an area of 21 km2 where fires have produced a mosaic of forest communities, including subalpine fir (Abies lasiocarpa), Engelman spruce (Picea engelmannii) and lodgepole pine, results from 255 track observations, 80 captures of 13 live-trapped martens, and scat analysis, over a 13 month period in 1973-1974, suggest that the mosaic of forest types created by wildfires improves the diversity and abundance of food during the summer, whilst mature forests of spruce and fir, with more than 30% canopy cover, provide shelter and food in winter.