Unit 131, Colorado

Elevation ranges from about 6,300 feet in the Yampa River valley lowlands to approximately 9,010 feet along the higher ridgelines abutting the Routt National Forest. Terrain consists of creek and river bottoms that rise gradually, separated by long north–south rimrock ridges and gradual mountain slopes broken by numerous benches. Some areas formerly mined by strip-coal operations have been reclaimed into rolling terrain and grassy uplands. The unit's eastern third grades into steeper Routt National Forest terrain; the western two-thirds is valley and foothill terrain typical of the upper Yampa basin.

The unit is approximately 83% private land; public hunting access is limited to scattered BLM parcels (totaling roughly 9% of the unit), State Trust Land sections (approximately 7%), and the 674-acre Emerald Mountain State Wildlife Area. Emerald Mountain SWA (GMU 131, Routt County, elevation 7,120–8,245 ft) is open July 16–November 30, foot or horseback only (no motor vehicles), closed Dec 1–July 15, and prohibits the discharge of firearms and bows—it provides fishing access and wildlife habitat, not hunting opportunity. Key highway corridors include U.S. Highway 40 (north boundary) and Colorado State Highway 131 (eastern boundary), which follows the Yampa River from State Bridge through Oak Creek to Steamboat Springs. Secondary county roads (including County Road 14, County Road 45, and Twenty Mile Road near Oak Creek) access private ranches and isolated public sections; 4WD is typically required on secondary roads. BLM's Little Snake Field Office administers scattered parcels within the unit. Most elk and deer holding on private ranch land may require trespass fees or landowner permission; hunting pressure is described as heavy throughout the upper Yampa area. No designated wilderness areas fall within GMU 131 proper.

Lowland areas carry sagebrush flats, hay and alfalfa meadows, and deep ravines thick with Gambel oakbrush, grasses, juniper, and pinyon pine; creek and river bottoms are lined with cottonwood and willow stands (important moose habitat). Foothills transition through mountain mahogany, bitterbrush, and scattered aspen with ponderosa pine. Higher elevations reaching toward the Routt National Forest boundary support lodgepole pine, spruce-fir, and aspen. The reclaimed strip-mine areas provide additional open grassland and shrub habitat.

Elk are the dominant big game species throughout the upper Yampa area; herds use Routt National Forest summer range to the east, migrating into the lower sagebrush and agricultural valleys of GMU 131 in fall. Bull numbers are adequate though large-antlered mature bulls are less common due to historical herd-reduction management emphasis. Mule deer are present throughout the unit, with the majority occupying western sections and some trophy-class bucks occurring in the southern portion; does and fawns use agricultural lowlands. Pronghorn occur in the sagebrush flats of the western and lower sections. Shiras moose use riparian willow corridors along streams and the Yampa River drainage; willow stands are key moose habitat here. Black bear range through the oakbrush and conifer zones, particularly near the Routt National Forest edge. Mountain lion are present but rarely encountered. Wild turkey inhabit oakbrush and ponderosa pine transitional zones.