Muskox are the largest member of the sheep and goat family. Bulls can stand up to five feet tall at the shoulders and can be six to eight feet in length. On average, bulls weigh between 270 and 315 kilograms, and cows about 90 kilograms less.
Both male and female muskox have impressive, sharp horns that curve downward toward the face, then out and up like large hooks. They begin to grow when a calf is four to five weeks old and continue until the muskox is about six years old, darkening with age. Bulls have a “boss” of bone up to 10 cm thick across their brow where the base of each horn meets. In cows, there is a tuft of white hair on the forehead that separates the less massive but equally sharp horns. Both the bulls and cows use their horns to dominate other muskox and to fight off predators.
Hidden in the wool in front of the eyes is a small scent-producing, pre-orbital gland that emits a strong musk scent when the animals are excited. As a display of dominance, bulls will rub their pre-orbital glands against the ground or their foreleg before they clash with another bull.
Muskox have a very thick dark brown or nearly black coat, known as guard hair, which can be as long as 24 inches. The guard hair covers the muskox completely except for the horns, hooves, lips and nose. Around the shoulders it is extremely shaggy, forming a distinct mane particularly noticeable on bulls. Behind the shoulders is a white or creamy yellow "saddle" and the lower legs have “stockings” that are light brown to white in colour.
Underneath the guard hair lies an extremely fine underwool known as qiviut. It is eight times warmer than sheep’s wool and finer than cashmere. In anticipation of warmer summer days approaching, muskox shed their qiviut in the spring. It gathers on bushes and shrubs creating a snow like appearance across the land. New qiviut grows throughout the summer and by August, muskox are once again ready for another long and cold winter.
These animals also have several other adaptations enabling them to survive the harsh Northern winters. Short, stocky legs and large, rounded hooves allow them to move easily through shallow snow and navigate rocky surfaces. They have small furry ears and a very short tail hidden beneath their coat. Muskox have keen sight, which is beneficial during the long winter darkness, and an acute sense of smell enabling them to find food beneath the snowy surface.