Habitat & Diet Selection

During 1999–2005, we collaborated with Montana State University to estimate absolute probabilities of use for winter habitats by pronghorn to assess if selection of sagebrush types has changed since the late 1980s, corresponding with diminishing sagebrush and increasing seral species such as rabbitbrush. Pronghorn selected intermediate elevations and slopes, preferred greasewood (Sarcobatus vermiculatus), and avoided sagebrush in comparison to the grassland cover type. The avoidance of sagebrush, which is highly important to other wintering pronghorn populations, may stem from a substantial decrease in this plant type on the winter range by the 1960s due to intense browsing by congregated ungulates. The percent composition of sagebrush in the winter diets of pronghorn, based on microscopic examination of plant fragments in feces, decreased from 67% during 1985–1988 to <10% during 2000–2001, while rabbitbrush increased from 5% to 60%. We are also collaborating with Montana State University, University of Idaho, and Yellowstone Ecological Research Center to estimate absolute probabilities of use for migratory, neonatal, and summer habitats, as well as to assess diet selection and quality. This information is essential for developing effective management strategies to conserve this Native Species of Special Concern.