Fur trade marten furs could generate in international markets spurred a "fur fever" in which many Russians moved to Siberia as independent trappers. From 1585 to 1680, tens of thousands of sable and other valuable pelts were obtained in Siberia each year. The primary way for the Muscovite state to obtain furs was by exacting a fur tribute from the Siberian natives, called a "yasak". "Yasak" was usually a fixed number of sable pelts which every male tribe member who was at least fifteen years old had to supply to Russian officials. Officials enforced "yasak" through coercion and by taking hostages, usually
American marten martes"). Specific predators vary by geographic region. In Newfoundland, red foxes ("Vulpes vulpes") were the most frequent predator, though coyote ("Canis latrans") and other American marten were also responsible for some deaths. In deciduous forests in northeastern British Columbia, most predation was attributed to raptors. Of 18 American marten killed by predators in northeastern Oregon, 8 were killed by bobcats ("Lynx rufus"), 4 by raptors, 4 by other American marten, and 2 by coyotes. Throughout the distribution of American marten, other predators include the great horned owl ("Bubo virginianus"), bald eagle ("Haliaeetus leucocephalus"), golden eagle ("Aquila chrysaetos"), Canada lynx ("L.