Characteristics of Bitterbrush Habitats that Influence Canopy Cover and Mule Deer Browsing

A step-wise multiple regression procedure was used to determine relationships of habitat characteristics to bitterbrush (Purshia tridentata [Pursh] DC.) cover and browsing by mule deer (Odocoileus hemionus hemionus). Eighteen environmentally different bitterbrush stands were studied on the Mount Haggin Wildlife Management Area in south-western Montana. Live and dead bitterbrush canopy cover at the 18 sites averaged 35 and 10%, respectively. Five variables (r2=0·79) and four variables (r2=0·75) accounted for most of the variation in live and dead bitterbrush canopies. Bitterbrush comprised an average of 53% of mule deer winter diets while five variables (r2=0·85) largely determined the level of browsing. The range of 57 to 96% utilization (80% average) was largely attributable (r2=0·69) to elevation and diversity of forage sources. Density of deer pellets was closely related to utilization and largely explained (r2=0·85) by three bitterbrush characteristics and elevation. The relationships found in this study should enhance management of bitterbrush habitats for mule deer production.