More closely related to sheep and goats than oxen, the muskox originated in Eurasia, and came across the Bering Sea 100,000 to 200,000 years ago to North America. These populations are the only ones that survived, dying out 9,000 years ago in Sweden 2,00 years ago in Siberia. Like the mammoths and other megafauna, Eurasian populations of muskox were likely wiped out by hunting, rather than climate.
In 1932, muskox were reintroduced to Sweden, but then hunted out during WW2. A second try in Norway 15 years later was successful and they eventually spread into Sweden in the 70s. While attempted introductions in Iceland and on Svalbard Island were unsuccessful, the Russians managed to established a number of healthy populations above the arctic circle in Siberia, where they continue to spread.
Historically, wolves weren't the only predators of muskoxen - they would have made a tasty meal for American lions (25% larger than modern lions) as well. Though not the typical prey for bears, muskox can serve during lean times, and the young are most vulnerable to attacks from both polar a grizzly varieties. Though they could potentially achieve 20 years or more, the harsh realities of the wild rarely allow this. Muskoxen may often fall victim to accidents associated with the hostile arctic lands -drowning, falling from cliffs, or starvation if ice or deep snow prevents access to the ground. The males typically die even younger due to the sometimes fierce fights over access to females.
