Muskoxen have a low reproductive rate with single calves born annually or every 2 to 3 years. At 3 years of age, cows normally bear their first calf. Environmental factors such as availability of food and severity of weather affect the age of first breeding and whether calves are born annually or at longer intervals.
Wolves, bears, and man are the primary predators of muskoxen. They are also vulnerable to accidents, such as falling from cliffs or drowning, and starvation if deep snow or ice covers their food. Cows may live more than 20 years, but the average lifespan is much less. On the average, bulls probably die at a younger age than cows due to the increased risks during fights over females. Muskox populations were extirpated from Alaska in the late 1800s, and apparently declined in Canada and Greenland by the early 20th Century. Although scientists are not sure about the exact causes of the decline, hunting and climatic changes may have been factors.
Muskoxen have historically been associated with the hunting cultures of early humans. Their meat and hides were used for food, clothing, and shelter, while the horns and bones were carved to make tools and crafts. They currently roam the arctic tundra of northern Canada and Greenland and have been successfully returned to Alaska and Russia. A small introduced population also exists in Scandinavia. Concerns that the muskox could become extinct resulted in efforts to reintroduce the species into areas of its former range. A small number of muskoxen originally from Greenland was reintroduced on Alaska's Nunivak Island in 1935-1936. The population grew over the years and supplied animals for other reintroduction efforts in northern Alaska from 1968 to 1981.
Today, a population of about 2,300 muskoxen resides in Alaska. Muskoxen also have been reintroduced in Russia, to Wrangell Island and on the Tamayr Peninsula. Worldwide, muskoxen now number about 125,000.