SUMMER DIET COMPOSITION OF MOOSE IN ROCKY MOUNTAIN NATIONAL PARK, COLORADO

Abstract

Summer diet composition of habituated adult moose (Alces alces) in Rocky Mountain National Park, Colorado, was determined using direct observations and fecal analysis. Direct observations determined moose ate 20 different plant species, including 6 willow (Salix spp.) species, which comprised 91.3% of the overall diet from June through mid-September. Geyer willow (Salix geyeriana) accounted for 45.1% of summer diets. Other species included mountain alder (Alnus incana, 2.5%), quaking aspen (Populus tremuloides, 1.1%), and bog birch (Betula glandulosa, 1.0%). Aquatic plants accounted for 1.9%, forbs 1.1%, and grasses 0.9%. Moose ate 11 different species of woody browse, which comprised 96.9% of the diet. Species diversity in the diet peaked in July with 18 different species, including 7 species of non-woody browse. Fecal analysis showed moose consumed 79.3% willow; 11.9% less than direct observations indicated. Fecal analysis identified Carex spp. as a major contributor to moose summer diets (8.7%); a genus not identified by direct observation. Fecal analysis could not identify forbs, willow, or other shrubs to the species level, but identified all major genera (> 1%) contributing to moose summer diets that were indicated by direct observations, except quaking aspen (1.1%).