Forests of Douglas-fir, Engelmann spruce, limber pine, and subalpine fir grow in some areas. During the summer, the mountain meadows display a variety of wildflowers, including the fringed gentian, Indian paintbrush, monkey flower, and mountain bluebell. More than 275 species of birds and nearly 50 kinds of other animals live in the park. Trumpeter swans, blue herons, white pelicans, bald eagles, and gulls feed on fish in its lakes and rivers. These fish include cutthroat trout, grayling, mountain whitefish, and rainbow trout.
Elk are the most common of the large animals in the park.
Approximately 31,000 elk live in the park in summer. About half of them stay there through the winter, but the rest wander south to warmer areas. Yellowstone has about 2,400 bison. These animals were widely hunted in the United States during the 1800's. The protection provided by the park helped save them from being killed off completely.