Siberian fur trade to overhunting. Instead of one sable pelt, the following was accepted as its equivalent: one fox, glutton (relative of the marten), or otter pelt; two blue-fox pelts; sixteen polar-fox pelts; or one hundred squirrel pelts. The Russian government decided the amount of other pelts that were equivalent to the sable pelt. Within forty years, almost all Siberian natives were forced into paying fur tribute to the Russians. Russian traders, hunters, and explorers reached the Pacific coastline by 1650 and were collecting fur tribute from most natives along the coast. Beyond the yasuk, the Russians had two principal ways of obtaining
American marten the larger fisher. The Newfoundland subspecies of this animal ("Martes americana atrata") is considered to be threatened. The Pacific Northwest subspecies, the Humboldt marten, is even more so, with only a few hundred individuals remaining. Compared to other carnivores, American marten population density is low for their body size. One review reports population densities ranging from 0.4 to 2.5 individuals/km. Population density may vary annually or seasonally. Low population densities have been associated with low abundance of prey species. Home range size of the American marten is extremely variable, with differences attributable to sex, year, geographic area, prey availability, cover