The young marten's eyes do not open until they are 5 to 7 weeks of age. By early fall the young martens can forage for themselves. Young normally mate for the first time when they are 2 years old and bear young in their third year. Some females may breed at 15 months. Home ranges of the marten vary in size in response to population levels and food availability.
Males typically travel greater distances than females.
Home ranges are exclusive within sexes except during the breeding period. While hunting for food, marten follow the fringes of spruce thickets along streams or the edges of bog meadows. Movement patterns during these forays are erratic and seemingly aimless. When crossing open swamps, lakes, or bogs, the marten uses every tree for cover, perhaps for protection from large carnivores and birds of prey. Marten are very courageous, but when pressed closely in open areas they may burrow into loose snow and tunnel for long distances beneath the surface.