While the lower elevations are often covered in grasses and sagebrush, higher altitudes support Douglas fir, with several species of spruce, cottonwood and aspen being the dominant tree species. Of the of streams and rivers there are major tributaries of the Yellowstone River, which bisects the western and eastern sections of the forest running through Paradise Valley. The Gallatin and Madison Rivers, major tributaries of the Missouri River, also are found in the forest. The habitat supports over 300 wildlife species, including the grizzly bear, bald eagle, and peregrine falcon. Many western North American species are represented in this climax ecosystem including elk, mule deer, bison, moose, bighorn sheep, pronghorn, cougar, gray wolf and black bear. Various subspecies of trout are plentiful in the streams and they contribute to the forest being one of the preeminent fly fishing regions in the United States.