For thousands of years, grasslands supported staggering numbers of bison, from the giant species of 10,000 years ago to the smaller animals of today, and as North America's largest land animal the buffalo dominated life on the Great Plains. In 1851, Chief Yellow Wolf reported that starvation stalked the Cheyenne villages and said the buffalo had disappeared from the foothills of the mountains to the forks of the Platte. Twenty years later, Colorado's eastern plains, once alive with tens of millions of buffalo, had none at all. Their disappearance had complex causes, but mostly resulted from human intervention, both Indian and white, through killing too many buffalo for their hides and altering or destroying too much habitat. Native peoples of eastern Colorado had long lived in a fragile balance on the dry plains, with Cheyennes, Arapahos, Kiowas, Comanches, Plains Apaches, and Shoshones using swift, durable ponies to hunt buffalo, pronghorns, deer, and elk, moving constantly among water sources and greener pastures in rhythm with the herds. That mobile way of life endured until railroads, towns, ranches, and farms cut through the land and permanently changed the relationship between native peoples and their high plains home.