Unit 31, Colorado

Elevation ranges from approximately 5,250 feet along the Colorado River corridor near I-70 up to about 9,035 feet at the higher Book Cliffs ridgelines. The unit is characterized by dramatic relief: sheer rimrock cliffs rising roughly 1,000 feet from canyon floors, steep-sided canyon country, long ridges, mesas, plateaus, and alkali flats. Rolling sagebrush benches and draws transition sharply into rugged pinyon-covered slopes and canyon walls. A portion of the Colorado River forms part of the southern boundary. Forum hunters describe ridges that 'go straight up and down and cliff out in a lot of places,' requiring serious physical conditioning.

GMU 31 is administered primarily by the BLM Grand Junction Field Office (970-244-3000) for the southern Mesa County portion and the BLM White River Field Office in Meeker (970-878-3800) for the northern Rio Blanco and Garfield County portions. The unit contains approximately 256,000 acres of BLM land and about 2,048 acres of Colorado State Land Board ground; the remaining roughly 44% is private, including large contiguous blocks held by ranches such as High Lonesome Ranch, which creates access checkerboard situations on BLM parcels. The main paved corridor is Interstate 70/US-6 along the Colorado River forming the southern unit boundary near De Beque. Colorado Route 64 west of Meeker and County Road 5 south (to CR 26) reach the Piceance State Wildlife Area (approximately 5,000 acres) on the northern edge. County Road 204 runs northwest-southeast from De Beque and is a primary access spine into the BLM interior. Douglas Pass (Colorado Hwy 139) connects to the western unit boundary. Remote interior areas require foot travel, horseback, ATV, or high-clearance 4WD; wet weather creates extreme mud on many roads and snow above roughly 8,000 feet can make roads impassable. Energy development (oil shale/gas) has created an extensive road network in the Piceance Basin portion, providing vehicle access to previously remote areas but also fragmenting habitat.

Lower elevations (roughly 5,000–6,500 feet) support pinyon-juniper woodland interspersed with sagebrush flats, alkali draws, and riparian cottonwood-willow corridors along creek drainages. Mid-elevation slopes (6,500–8,000 feet) transition to oakbrush (Gambel oak) with scattered ponderosa pine. Higher terrain holds aspen stands and pockets of spruce-fir. The Book Cliffs escarpment supports dense oakbrush, cedar/juniper, and brush that burned extensively in the 2020 Pine Gulch Fire (at the time the largest wildfire in Colorado history), opening much of the mid-elevation burn scar into early-successional shrub and forb habitat that concentrates deer and bears. Natural springs and water tanks are scattered but limited, concentrating wildlife movements.

Mule deer are the signature species; the Piceance Basin is critical winter range for one of Colorado's largest migratory mule deer herds, historically regarded as among the most significant mule deer migration concentrations in North America. Deer are distributed on northern portions of the unit from mid-October, with early-season animals at higher elevations and later-season concentrations moving to lower south-facing slopes and canyon country in the Little Hills and Dry Fork of Piceance area when snow arrives. Rocky Mountain elk are present in substantial numbers; the best elk habitat is in remote high-elevation pockets of aspen and spruce-fir, with hunting pressure and weather pushing bulls into lower pinyon-juniper during later rifle seasons. Black bears are present seasonally, particularly in oakbrush and berry-producing burn scars post-Pine Gulch Fire. Mountain lions are present, following deer concentrations. Pronghorn occupy sagebrush flats and the gentler basin terrain. Turkey are present in pinyon-juniper and riparian zones. CWD (Chronic Wasting Disease) has been detected in the unit; hunters are encouraged to participate in voluntary testing.