Above the tree limit and around snowfields and glaciers lies the alpine tundra. This fragile ecosystem challenges plant and animal survival with temperature extremes, high winds, a short growing season, frequent drought, and poor soil. Basic plant survival adaptations include dwarfism, oversize root systems, matting growth, succulent leaves or stems, and warmth-producing red pigments. Some high mountain plants are almost brown, not green, but perfectly alive. Dwarfism and matting keep plants snugged low to the ground where conditions are less severe than just a few centimeters higher. Animals tend to adapt to subalpine and alpine rigors by modifying their behavior rather than their structure. Exceptions include flightless grasshoppers and the pika’s fur-covered feet. The summer alpine tundra provides insects, seeds, leaf crops, lichens, and fungi as wildlife food. For this short season animals are well supplied and may become conspicuous. Birds, with their advantage of flight, can cover vast areas quickly in the search for food. They can also readily change ecozones. A bird flying from alpine tundra down to a forested slope makes a journey between ecozones equivalent to migrating from above the Arctic Circle to northern Maine. Hawks and eagles, in a regular search for pikas or mice, can cover all of the Teton high peaks in 2 hours or less. [Illustration: _Plants and animals of the mountain world:_] 1 _Prairie falcon_ 2 _Pika_ 3 _Yellow-bellied marmot_ 4 _Cushion buckwheat_ 5 _Whitebark pine_ 6 _Subalpine fir krummholz_ 7 _Dwarf willow_ 8 _Pixie-cup lichen_ 9 _Black rosy finch_ 10 _Alpine forget-me-not_ 11 _Moss campion_ 12 _Haircap moss_ [Illustration: Wary bighorn sheep are the largest mammals of the high mountain realms. The male’s horns, curved back, down, and around, may cap a 135-kilogram (300-pound) body. Sheep wear thick, tannish-gray hair. Their specialized footpads enable them to scale rock that might stymie a roped alpinist. Rams and ewes hold to separate bands except during the mating period. Generations of sheep will occupy the same range. The Teton population, numbering between 100 and 125 animals, is wary because the sheep are hunted in fall on adjacent national forest lands. Hikers and climbers occasionally see them on the range’s east side, but you will not see bighorn sheep from your car except sometimes in the winter when they may move down into Jackson Hole.] [Illustration: _Autumn aspens lend what prospectors never found in this valley—large touches of gold._] The Valley