Winter Diets of Mule Deer in Relation to Bitterbrush Abundance

Abstract

During the winters of 1974-1975 and 1975-1976 food habits of the Entiat mule deer (Odocoileus hemionus hemionus) herd were quantified in sites with high, medium and low antelope bitterbrush (Purshia tridentata) abundance. Using a microscopic technique, 27 plant species were identified in fecal samples. Bitterbrush, buckwheat (Eriogonum spp.), arrowleaf balsamroot (Balsamorhiza sagittata) and lupine (Lupinus spp.) combined made up 87%-93% of the diet in the three sites. Bitterbrush use was heavy in sites where it was available; however, as its availability declined, buckwheat replaced it in the herd's diet. In the site with a low bitterbrush abundance lupine also replaced bitterbrush in the herd's diet. Balsamroot use remained relatively constant in all sites during both winters. Changes in bitterbrush abundance significantly affected the diet of the mule deer herd; however, these changes were not thought to adversely affect the winter survival of the deer herd.