Unit 18, Colorado

Elevation ranges from approximately 7,500 feet on the lower Colorado River benches to over 13,000 feet along the Continental Divide; North Arapaho Peak reaches 13,502 feet in the southeast corner of the unit. Terrain is predominantly steep to very steep mountain country — the peaks of the Continental Divide form the backbone. The interior is deeply dissected by the Troublesome, Antelope, Corral, and Willow Creek drainages, all funneling west toward the Colorado River and through Gore Canyon downstream of Kremmling. The roadless central portion is the most rugged; the southern and eastern margins are more roaded and accessible by four-wheel-drive vehicles. Rocky Mountain National Park borders the eastern edge but is closed to hunting. All natural surface drainage funnels through Gore Canyon, downstream of Kremmling.

The unit is administered primarily by the Sulphur Ranger District of the Arapaho and Roosevelt National Forests (office in Granby, 970-295-6600) and the Kremmling Field Office of the BLM. A portion of the federal lands within the DAU is also administered by the Parks Ranger District of the Medicine Bow/Routt National Forest. Rocky Mountain National Park occupies a large block of the eastern unit and is closed to hunting; hunters must not enter RMNP with weapons or establish hunting camps there. The Never Summer Wilderness and Indian Peaks Wilderness areas are partly within or adjacent to the unit. The Bowen Gulch Protection Area is also within the unit, administered by the USFS. Key highway access: US Highway 40 runs east-west through the southern portion (Granby to Kremmling); Highway 125 provides north-south access through the interior; Highway 34 connects Grand Lake northward toward the RMNP boundary in the eastern unit. USFS Road 103 (Troublesome Creek area) provides western interior access off US 40. Primitive roads reach the heads of most drainages into the Colorado River, most passable by four-wheel-drive vehicles. Numerous National Forest trailheads serve backpack and horseback hunters seeking roadless central areas. Private land concentrates in valley bottoms, irrigated hay meadows, and lower river corridors; per the CPW E-8 HMP, GMU 18 is approximately 18.2% private (49,178 of 405,138 acres) and limits lower-elevation winter-range access, particularly along the Colorado River between Granby and Kremmling. Conservation easements protect approximately 12,938 acres of private land within the DAU. Verify current USFS travel management road closures with the Sulphur Ranger District before hunting. Winter snowmobile use is extensive throughout the unit.

Vegetation transitions through five broad types with elevation. Sagebrush steppe and mountain shrub (big sagebrush, serviceberry, chokecherry, antelope bitterbrush) dominate valley floors and lower hillsides up to approximately 9,000 feet, providing critical winter range for deer and elk; bluebunch wheatgrass is prominent under good range conditions. Riparian corridors along the Colorado River between Granby and Kremmling support narrowleaf cottonwood and willow — the most diverse wildlife habitat in the unit despite being least-represented in acreage. Lodgepole pine is the most broadly distributed forest type (roughly 7,500–10,500 feet); mountain pine beetle mortality beginning approximately 1998 killed over 90% of mature stands, dramatically increasing grass and forb understory, altering elk distribution by increasing use of the lodgepole zone especially during fall, spring, and average winters. The 2020 East Troublesome Fire further remapped cover across a large swath of the unit, opening additional browse and forage areas while eliminating timbered elk cover in heavily burned drainages. Aspen stands occur at mid elevations up to 10,500 feet, providing important cover and forage; Engelmann spruce and subalpine fir occur at higher elevations providing excellent summer cover. Pinon-juniper woodland appears on some lower slopes and provides cover and low-quality forage. Alpine tundra and krummholz occupy ridges and peaks above approximately 11,000 feet, serving as high-quality elk summer forage from July through early September. Irrigated hay meadows (timothy, smooth brome) occupy valley bottoms and contribute important winter congregation areas along private ranch corridors.

Elk and mule deer are the primary big game species and are present year-round; elk are managed under CPW Data Analysis Unit E-8 (Troublesome Elk, GMUs 18 and 181) and deer under D-9 (Middle Park Deer, GMUs 18, 27, 28, 37, 181, 371). The 2009 post-hunt elk population estimate for the entire E-8 DAU was approximately 3,970 animals with a new management objective of 3,600–4,300; bull-to-cow ratios have averaged 25 bulls per 100 cows from 1991–2009, with a 5-year average of 23.4 bulls:100 cows. A 4-point antler restriction has been in effect in E-8 since 1986. Elk summer in high-elevation spruce-fir and alpine meadows and migrate downslope to BLM and private sagebrush-steppe winter range; a significant portion concentrates on low-elevation private lands near Kremmling in severe winters. RMNP provides an unhunted refuge on the eastern margin, and RMNP-resident elk cross into GMU 18 seasonally, complicating management. Overall hunter success in E-8 averaged 13% between 2000 and 2009 (vs. 16% in the 1991–1999 period), with mean total harvest of 821 elk per year from 1991–2009 (both GMUs 18 and 181 combined). The mule deer D-9 DAU post-hunt population was estimated at 16,668 in 2019 (above objective), with bucks-to-does averaging approximately 39–40 bucks:100 does. Key mule deer wintering areas include the southern end of GMU 18 and lower-elevation sagebrush. Moose inhabit riparian corridors and willow parks, especially near Grand Lake, Lake Granby, and along the Colorado River headwaters. Black bear occupy the forested upper and mid elevations; mountain lions are present but rarely seen. Bighorn sheep occupy rocky ridgelines along the Continental Divide. Pronghorn occur in small numbers in Middle Park sagebrush flats. The 2020 East Troublesome Fire significantly altered elk and deer movement patterns; post-fire grass and forb regeneration in burned lodgepole has attracted animals into formerly timbered areas, while islands of unburned timber provide refuge.

1. Elk hunter success (13%) and mean harvest (~821/year) are for the entire E-8 DAU (GMUs 18 AND 181 combined), per the 2010 CPW HMP; GMU 18-only figures are not publicly broken out. The draft's 9% success and 680 harvest figures were not supported by any source reviewed and have been removed. 2. Mule deer success rate removed — the 27% figure was the D-9 DAU 6-GMU average and not GMU-18-specific. 3. Land ownership for GMU 18 per HMP Table 1: 18.2% private (49,178 ac), 51.8% USFS (210,196 ac), 23.6% NPS (96,521 ac), 11.0% BLM (44,705 ac), 0.4% CDOW/SLB (1,777 ac) — total 405,138 acres. Public land pct stored as 82 (rounds 81.8%). 4. Mountain pine beetle onset corrected from 'around 2002' to 'approximately 1998' per HMP text ('within the past decade' as of 2010). 5. The Rabbit Ears Mountains reference was removed from GMU 18 terrain — they lie primarily in GMU 181 territory to the west. 6. 3rd rifle season end date corrected to November 15 (not November 17). 7. Non-resident archery elk confirmed draw-only since 2025; resident archery OTC confirmed. 8. All population data is pre-East Troublesome Fire (October 2020); current populations may differ substantially. 9. Tag quotas not available in public CPW harvest reports reviewed.