Dominated by sagebrush grasslands, the high cold desert provides habitat for one of the largest pronghorn antelope herds in the world. This region is home to 40,000 to 60,000 antelope, known as the Sublette Herd. The pronghorn has keen eyesight and the ability to run up to 60 miles an hour. Small groups of the herd can be viewed during the late spring and summer. As fall turns into winter and snow begins to cover their food sources, thousands of pronghorn begin migrating south to open areas to feed. In one of the longest big game migrations in North America, some segments of the herd migrate up to 200 miles. From as far north as Grand Teton National Park south to Rock Springs, much of the migration parallels this highway, a route favored both by pronghorn and humans. The Sublette Herd survives the harsh conditions of the high cold desert by traveling long distances, making an open migration route crucial to its survival.