Mule Deer US FWS. Mammals - Great Basin National Park (U.S. National Park Service) Looking out across the valleys of the Great Basin and its vast stretches of sagebrush and desert, one would hardly imagine that 70% of all North American mammals are found in this region. From the kangaroo rat, which can survive without ever drinking water, to the mountain lion that slips through the forest on silent paws, the variety of wildlife is astounding. Don't expect to observe all of these animals at once, as many are secretive and low in population density. Although, with a little luck, correct timing, and patience, a wide array of creatures may present themselves as you hike or drive across the area.