The Newfoundland marten is genetically distinct from the American marten. American marten may be nocturnal or diurnal. American marten are well adapted to snow. The fisher is closely related to, but larger than, the American marten ("Martes americana"). High American marten mortality in Newfoundland was caused by encephalitis. American marten may travel extensively under the snowpack. Adult American marten are generally solitary except during the breeding season. American marten diet may shift seasonally or annually. American marten in captivity may live for 15 years. American marten have a roughly triangular head and sharp nose. Dall sheep, hoary marmot, American black bear, American marten, and long-tailed chickadee are noted. American marten are vulnerable to predation from raptors and other carnivores. American marten are particularly vulnerable to trapping mortality in industrial forests. In Canada and Alaska, American marten distribution is vast and continuous. American marten commonly den in hollow logs.