Mule Deer and Elk Foraging Preference for 4 Sagebrush Taxa

Abstract

A 10 year study under natural winter conditions at 2 sites tested the hypothesis that mule deer (Odocoileus hemionus hemionus) and elk (Cervus elaphus nelsoni) forage equally on 4 sagebrush (Artemisia L.) taxa. Each year approximately 2,500 available leaders on 244 plants on the Northern Yellowstone Winter Range were examined for browsing. Browsing levels increased with winter severity, reaching 91% of leaders browsed for mountain big sagebrush (A. tridentata ssp. vaseyana [Rydb.] Beetle), the preferred taxon (p< 0.05) that averaged 56.1% at the 2 sites. Wyoming big sagebrush (A.t. ssp. wyomingensis Beetle and Young) was narrowly preferred (38.6%) over basin big sagebrush (A.t. Nutt. ssp. tridentata) (30.3%). Black sagebrush (A. nova Nels.) was least preferred (17.0%). Differences in preference among taxa were smallest during the severest winters when more elk were present thereby increasing total sagebrush utilization. Mule deer diets averaged 52% sagebrush over the study. Many sagebrush plants were damaged and even killed by heavy browsing during the study. Promoting sagebrush productivity should be a management objective on similar winter game ranges.