According to the expert what challenges did mountain men face

The life of a mountain man was rugged: many did not last more than several years in the wilderness. They faced many hazards, especially when exploring unmapped areas: biting insects and other wildlife, bad weather, diseases of all kinds, injuries and hostile tribes presented constant physical dangers. Grizzly bears were one of the mountain man's greatest enemies. Winters could be brutal with heavy snowstorms and low temperatures.