Muskoxen are well adapted to their cold Arctic habitat, with short, stocky bodies and a thick coat of ground-length hair, enhanced in the winter by woolly underhairs for added insulation. They feed on sedges, grasses, and willows. Like other mammals in the family Bovidae, they are ruminants: they gulp down a large quantify of food, then regurgitate and re-chew it at leisure. This behavior - chewing their cud - lets them break down the vegetation and digest it better. It also lets them forage quickly, which may be a protection from predators. Females and young Muskoxen live in mixed-sex groups year-round. Some bulls live alone in the summer, but are likely to join all-male or mixed-sex groups in winter. Bulls breed with several females. Competition involves clashing with horns and their heavily shielded heads. Muskoxen also use their horns in a group defense strategy against their principle predators, wolves and brown bears: they back into a circle or cluster, with head and horns facing outward. Individual animals dart out to charge at the intruder.

Links:
Mammal Species of the World
Click here for The American Society of Mammalogists species account