West of the 100th Meridian, the Great Plains of North America become semiarid. The rain shadow of the Rocky Mountains, higher elevations and an increasing distance from the Gulf of Mexico combine to limit annual precipitation to 20 inches or less. Stretching from eastern Montana to West Texas and eastern New Mexico, this province is the domain of the Shortgrass Prairie; blue grama and buffalo grass dominate, with pockets of sand dropseed, three-awn, sideoats grama and western wheatgrass. Saltbush, chokecherry, winterfat and groves of cottonwood line the drainages while yucca, prairie sunflowers, prickly pear and Indian paintbrush add color to the landscape. Today, most of this province has become a mosaic of irrigated croplands and cattle ranches.
The Pawnee National Grasslands, in northeastern Colorado, is one of the better places to explore what remains of the shortgrass prairie. Stretching north of Colorado 14, between Ault and New Raymer, the Grasslands are accessed by a network of dirt-gravel roads. Early or late day visitors should see coyotes, mule deer, white-tailed deer and, if you're lucky, swift fox; other resident mammals include pronghorn, black-tailed prairie dogs, badgers, jackrabbits and thirteen-lined ground squirrels. Bull snakes and prairie rattlers are often seen along the roadways and cattle, surrogates for the great bison herds, roam the prairie from May through October.
McCown's and chestnut-collared longspurs, western meadowlarks, horned larks, lark buntings, killdeer, spotted sandpipers, long-billed curlews, avocets and mountain plovers characterize the bird population. Raptors include golden eagles, Swainson's hawks, prairie falcons, American kestrels, ferruginous hawks, great horned owls and burrowing owls; the latter nest in abandoned prairie dog burrows and feast on the numerous grasshoppers.
