Sex, age, and seasonal differences in the diets and activity budgets of muskoxen (Ovibos moschatus)

Abstract

During the spring–summer period on Banks Island, Northwest Territories, Canada, muskoxen (Ovibos moschatus) in mixed age–sex herds spent similar amounts of time foraging and resting. However, calves foraged less and rested more than adults and yearlings, and dominant rutting males foraged less but spent more time in active nonforaging behaviours than other adults. Based on fecal analysis, adult females, subadults, yearlings, and calves each consumed proportionately more dicotyledonous forages (dicots) than adult males. For adult females, subadults, and calves this was due to a proportionately greater consumption of forbs; for yearlings it was due to their proportionately greater use of both shrubs (mostly Salix spp.) and forbs. The feces of yearlings contained a significantly higher proportion of dicots (especially shrubs) than those of adult females, and those of juveniles a higher ratio of Salix leaves to stems than those of adults. Adult male feces contained a significantly greater proportion of sedges and rushes than those of adult females or calves, while the feces of adult females and calves contained significantly more sedges and rushes than those of yearlings. There was a seasonal decline in dicot consumption for all muskoxen except adult males. These age–sex differences in fecal composition were consistent with behavioural observations of time allocated to foraging in dicot-dominated habitats and suggest that young muskoxen and adult females satisfied their particular nutritional requirements by specifically selecting dicot-dominated habitats within the areas occupied by mixed age–sex herds.