Summer foraging ecology of wapiti (Cervus elaphus roosevelti) in the Mount St. Helens blast zone

Summer–fall foraging behavior of wapiti was studied relative to seasonal changes in forage resources in early successional forests of the Mount St. Helens "blast zone." Seasonal changes in diet, plant community selection, and foraging behavior of wapiti were generally consistent with hypothesized ingestive and processing constraints on a large-bodied ruminant. When high-quality forage was abundant early in the growing season, forbs dominated in wapiti diets probably because of their high digestibility and cell-wall breakdown rates. As forb biomass declined, wapiti initially maintained a high intake of forbs by increasing search rates (m/min). Eventually wapiti switched to grasses, with consequent decreases in feeding time and increases in rumination time. Selection of plant communities by wapiti was related to the standing crop (kg/ha) of forage only in the fall, when grasses were the preferred forage type. Cover and spacing needs during calving and the influence of forage structure on intake rates and plant community selection are discussed.