Seasonal Foraging Strategies of Migrant and Non-Migrant Pronghorn In Yellowstone National Park

Abstract

Abstract We characterized the seasonal composition and quality of migrant and non-migrant Pronghorn (Antilocapra Americana) diets in Yellowstone National Park during 2006–2007. During winter (January–April), when migrants and non-migrants occupied the same winter range, the overall percent relative density for each forage class in Pronghorn diets (n = 51 composite fecal samples) was 67 + 6% (standard error) shrubs, 17 + 3% forbs, 13 + 3% grasses, and 3 + 1% other. However, spring and summer diets differed for migrants and non-migrants. Diets of migrants (n = 34) to higher-elevation ranges with higher precipitation and forage quality during May–August were dominated by 68 + 2% forbs, whereas summer diets of non-migrants (n = 21) remaining on the winter range were co-dominated by 48 + 2% forbs and 42 + 1% shrubs. Diet quality for migrant Pronghorn, as indexed by fecal nitrogen and DAPA, was also generally higher than for non-migrants during a period when the demands of late gestation and lactation were high...