Colorado GMU 851 Mule Deer Hunting
Costilla and Las Animas counties, southeast Colorado · 438 sq mi
Based on the EASIEST unit-wide buck or either-sex hunt code available to adult Colorado residents in the 2026 primary draw — the lowest preference-point tier that drew reliably. Private-land-only and Ranching for Wildlife hunts are excluded because neither is a unit-wide public-land opportunity — NOT because the public cannot draw them. A private-land-only license requires the hunter's own permission to hunt private ground; a Ranching for Wildlife license is valid on the participating ranches enrolled in that program. They are separate systems. Other weapons, seasons and nonresident applicants can require substantially more points. The band is a floor, not a target: even the easiest qualifying hunt here sits in that range.
What hunting GMU 851 is like
GMU 851 spans 438 square miles across Costilla and Las Animas counties in the southeast region. Elevation ranges from 6,000 feet to 14,000 feet, with typical terrain at 7,900 feet. The unit is rolling to moderately steep, with 27 percent gentle slopes, 56 percent moderate slopes, and 17 percent steep terrain. The country supports mule deer across a broad elevation band, from lower montane to high alpine country.
Public hunting access is limited. Only about 12 percent of the unit—roughly 52 square miles—is generally open to public hunting. That ground consists of State Wildlife Areas, National Forest, and BLM land. The remaining 88 percent is private. The public acreage is scattered and interspersed with private holdings, so legal access and road conditions will determine where a hunter can actually reach and hunt.
Mule deer occupy the unit seasonally. Summer Range covers 100 percent of the unit, and Winter Range covers 81 percent. Winter Concentration layers mark 52 percent of the unit where mule deer cluster during the winter months. As the fall season progresses and temperatures drop through November—when average highs fall from near 72°F in September to around 51°F—mule deer shift toward concentrated winter grounds in response to cooling weather and snow accumulation. The concentration of deer intensifies as the season moves into November, when the Primary Rut occurs and mule deer begin consolidating on winter range.
The unit offers seven seasons: Archery (September 2–30), Muzzleloader (September 12–20), four Rifle seasons (October 10–14, October 24–November 1, November 7–15, November 18–22), and Ranching for Wildlife (no published dates). All are for bucks. The unit draws at Moderate difficulty—1 to 2 points for the easiest unit-wide buck code available to adult Colorado residents—though premium buck seasons require substantially more points. Hunter pressure is extreme.
Terrain & elevation
- Elevation
- 6,000–14,000 ft, typically around 7,900 ft
- Steepness
- Steep — mean slope 16.3°
- Slope breakdown
- 27% gentle · 56% moderate · 17% steep · 0% rugged
- Ground you can count on
- ~52 sq mi
Land & access
About 12% of GMU 851 is public land a hunter can count on — State Wildlife Areas, National Forest and BLM.
- State Wildlife Area11%
- National Forest<1%
- BLM<1%
- Unclassified ownership<1%
- Private88%
Where mule deer live in the unit
Colorado Parks & Wildlife maps mule deer seasonal ranges statewide. This is how much of GMU 851 each range covers — the single best clue to whether mule deer are here in September, in November, or only passing through. The layers overlap, so they do not add to 100%.
- Summer Range100%used in summer
- Overall Range100%the full extent of range CPW maps for mule deer — near 100% on most units, and not a statement about when mule deer are present
- Winter Range81%used in winter
- Winter Concentration52%where mule deer bunch up in winter
Mule Deer seasons & weapons (2026)
| Season | Dates | Tags offered |
|---|---|---|
| Archery | September 2 – September 30 | Buck |
| Muzzleloader | September 12 – September 20 | Buck |
| 1st Rifle | October 10 – October 14 | Buck |
| 2nd Rifle | October 24 – November 1 | Buck |
| 3rd Rifle | November 7 – November 15 | Buck |
| 4th Rifle | November 18 – November 22 | Buck |
| Ranching for Wildlife | Dates vary by hunt code | Buck |
Dates span every hunt code of that type in this unit and can differ by code. Confirm the current brochure with Colorado Parks & Wildlife before applying.
Fall weather
- September — highs around 72°F, lows around 43°F (mid-elevation normals)
- October — highs around 62°F, lows around 33°F, about 1.1 in of snow (mid-elevation normals)
- November — highs around 51°F, lows around 23°F, about 4.1 in of snow (mid-elevation normals)
GMU 851 mule deer hunting FAQ
Is this unit realistic for a hunter with zero preference points?
The easiest unit-wide buck code draws at 1 to 2 preference points, so a first-time applicant with zero points is unlikely to draw that hunt. However, the draw difficulty is Moderate rather than Hard, meaning the entry-point hunts remain accessible with just a few years of applications. Applicants should plan to build points or consider whether they can hunt the private-land-only or Ranching for Wildlife options.
How much ground can a public-land hunter actually hunt here?
Only about 12 percent of the unit is generally open to public hunting, totaling roughly 52 square miles. That public land consists of State Wildlife Areas, National Forest, and BLM parcels scattered across the unit. Private land makes up 88 percent, so a hunter's actual access depends on finding legal entry points and navigating around private inholdings.
Which seasons offer the best chance of finding concentrated mule deer?
Winter Concentration covers 52 percent of the unit, and mule deer consolidate most intensely from November through the Primary Rut (November 11–25) and into late November. The 3rd Rifle (November 7–15) and 4th Rifle (November 18–22) seasons fall directly in or near the Primary Rut and late-rut phases when bucks are actively seeking does and mule deer are shifting to concentrated winter grounds.
What is the terrain like for a hunter on foot?
The unit is rolling to moderately steep, with gentle terrain making up 27 percent and moderate slopes 56 percent, so the majority of the unit is walkable without extreme climbing. However, terrain difficulty is secondary here—legal access to public land is the limiting factor, since only about 12 percent of the unit is open to public hunting and the rest is private.
Do the early seasons (Archery and Muzzleloader) differ significantly from the rifle hunts?
Yes. Archery (September 2–30) and Muzzleloader (September 12–20) occur during the Velvet Shed phase when bucks are transitioning out of bachelor patterns and mule deer are not yet concentrating for winter. The four rifle seasons spread from mid-October through late November, progressing from the Nocturnal Buck Phase through the Primary Rut when bucks are actively chasing does and mule deer are moving toward winter range.
Should a hunter expect snow and cold in the later rifle seasons?
November brings real cold and snow to the unit. Average highs drop to around 50°F by November, and average snowfall is 4.1 inches per month. The 3rd and 4th Rifle seasons (November 7–15 and November 18–22) will almost certainly involve snow on the ground and freezing temperatures, which can favor hunters by concentrating mule deer and making tracking easier but will demand proper gear and preparation.
Data sources & methodology
- Colorado Parks & Wildlife — Big Game hunting — seasons, weapons, hunt codes and license types
- CPW — Primary Draw rules — how preference points and the hybrid draw work
- CPW — Deer statistics, draw recap and Drawn Out At reports — the point levels behind the draw-difficulty bands
- CPW — Secondary Draw — licenses remaining after the primary draw
- CPW — Maps and GIS (Species Activity Mapping) — mule deer seasonal range
- CPW — State Trust Land Finder — which State Trust acreage is enrolled and open to public hunting
- Federal and state land-ownership datasets — land ownership and access
- NOAA climate normals — fall weather
Draw difficulty is a qualitative band, not published odds — the note under the summary above states exactly which hunt code it describes. Land shares are separate, non-overlapping categories: publicly owned is not the same as open to hunting, and State Trust Land is huntable only where CPW has enrolled it. Unit data last updated August 31, 2026.