Unit 13, Colorado

Elevation ranges from approximately 6,300 feet in the valley bottoms near Craig and the Yampa River corridor to 12,000 feet along the Continental Divide ridgeline on the unit's eastern margin. The Williams Fork Mountains form the central spine, with steep, rocky dry gulches on the southern flanks and generally hilly, steep slopes throughout. Rolling foothills and alluvial flats characterize the western and lower-elevation portions.

Unit 13 is bounded on the north by U.S. Highway 40, on the east by Routt County Road 179, Trout Creek, and Fish Creek, on the south by Routt County Road 29 and Colorado Highway 317, and on the west by Colorado Highway 13. Craig (Moffat County seat) is at or immediately adjacent to the western boundary; Steamboat Springs lies to the east. The Routt National Forest — Hahns Peak/Bears Ears Ranger District (925 Weiss Drive, Steamboat Springs, CO; 970-870-2299) — administers the forested eastern portion. Public land is approximately 23 percent of the unit (7% BLM, 15% State Trust Land); the Routt NF acreage is included within that combined figure, not separately broken out. A roughly 20-mile band of BLM land runs parallel to Colorado Hwy 317 and the Williams Fork River from Hamilton east to Lone Gulch — this is the primary contiguous public hunting land in the southern portion. Scattered State Trust Land parcels provide additional access. Most land outside these public parcels is private ranch land. 4WD vehicles are typically required on secondary county and forest roads. Hunting pressure is heavy on the limited public parcels. There are no major wilderness designations within the core of GMU 13; Mount Zirkel Wilderness sits in adjacent units 4 and 5 to the north.

Lower elevations and valley flats are covered by sagebrush, short grasses, and dry-farmed or irrigated croplands. Rolling foothills support pinyon-juniper woodland, serviceberry, oakbrush, and sagebrush. Southern slopes are dry-aspect juniper, pinyon, oakbrush, and short grass; north-facing slopes transition into aspen stands mixed with oakbrush and open parks. The Routt National Forest portion carries coniferous forest (lodgepole pine, spruce-fir) and extensive aspen. The Yampa and Williams Fork river corridors support riparian willow and cottonwood.

Elk are the dominant large ungulate and are plentiful throughout the Upper Yampa unit group. Large concentrations occur on Routt National Forest land and private ranches. Elk move between summer range in the higher forested elevations of the Williams Fork Mountains and lower winter range in valley bottoms and private agricultural lands along the Yampa and Williams Fork rivers — this migration concentrates elk on private land during rifle seasons, which explains high private-land success rates and the prevalence of fee-hunting. Mule deer are present in lower densities, concentrated in the western foothills and sagebrush-oakbrush transition zones; buck numbers have shown improvement in the southern portions. Pronghorn inhabit the sagebrush flats and rolling foothills at relatively low densities; doe licenses have been closed due to herd recovery needs following the severe 2022-23 winter (Great Divide herd, which includes GMU 13, was significantly impacted). Shiras moose are present in riparian corridors along the Yampa and Williams Fork and are listed as a huntable species. Black bear are huntable as an add-on to archery or muzzleloader elk/deer licenses; GMUs 13 and 131 are confirmed bear add-on eligible units. Mountain lion and turkey are also listed as huntable species. CPW actively manages elk populations in this unit partly to reduce crop damage on private lands.