Wilderness of the North Cascades hosts wildlife less common in the more populated areas of Washington State. 75 mammal species in 21 families can be found in the North Cascades. Three species (gray wolf, grizzly bear, and Canada lynx) are listed as 'threatened' or 'endangered' under the Endangered Species Act. Grizzly bears and gray wolves have both been documented as residing in rugged terrain. Both are emblematic of the need for large contiguous areas of undisturbed wilderness that are necessary for these species to exist. Other species associated with wilderness areas that have been documented in the North Cascades include black bear, wolverine, river otter, cougar, lynx, and bobcat.