Colorado GMU 521 Mule Deer Hunting
Delta and Gunnison counties, northwest Colorado · 508 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 521 is like
GMU 521 spans 508 square miles across rolling to moderately steep terrain in Delta and Gunnison counties. Elevations range from 5,400 feet to 13,100 feet, with typical hunting grounds around 8,500 feet. The unit's terrain divides into 35 percent gentle slopes, 45 percent moderate slopes, 17 percent steep slopes, and 3 percent rugged terrain by area. This mix supports a variety of hunting approaches across different seasonal ranges and elevations.
The unit is approximately 75 percent open to public hunting on National Forest and BLM lands, with the remaining 25 percent held in private ownership. The U.S. Forest Service comprises 68 percent of the unit, BLM another 7.6 percent, and private lands make up the rest. Access varies by location and season; hunters should verify roads, trailheads, and any seasonal closures before planning a hunt.
Mule deer occupy summer range across the entire unit, and their overall mapped range also covers the full extent. Winter range is mapped on 15 percent of the unit, with winter concentration on 8 percent. This seasonal distribution indicates mule deer shift their use through the fall as conditions change, though exact timing and extent vary with weather and snow. During the archery and muzzleloader seasons in September, deer are in the velvet shed and early fall transition phase. The 2nd rifle season in late October falls during early fall migration and the nocturnal buck phase. The 3rd rifle season in November spans the early pre-rut period and the primary rut. The 4th rifle season in November 18–22 occurs during the primary rut phase.
The unit offers five public seasons: archery from September 2–30, muzzleloader from September 12–20, 2nd rifle from October 24 to November 1, 3rd rifle from November 7–15, and 4th rifle from November 18–22. All are buck seasons. One private-land-only season runs August 15 to November 15 and is not available on public ground. September temperatures average highs near 68 degrees and lows near 42 degrees with minimal snowfall. October brings cooler conditions with highs near 56 degrees and about 2.2 inches of monthly snowfall. November sees significant cooling and precipitation, with highs around 44 degrees and approximately 8.6 inches of monthly snowfall. The draw for this unit is easy, with the lowest preference-point tier for the easiest unit-wide buck code drawing reliably; hunter pressure is low.
Terrain & elevation
- Elevation
- 5,400–13,100 ft, typically around 8,500 ft
- Steepness
- Steep — mean slope 15.9°
- Slope breakdown
- 35% gentle · 45% moderate · 17% steep · 3% rugged
- Ground you can count on
- ~382 sq mi
Habitat & cover
What actually grows here, by elevation. Each band adds to 100% on its own — these are shares of that band, not of GMU 521.
Lower elevations
- Aspen40%
- Sagebrush35%
- Conifer14%
- Other cover8%
- Riparian2%
Mid elevations
- Aspen81%
- Sagebrush10%
- Conifer7%
- Other cover1%
Higher elevations
- Aspen40%
- Conifer38%
- Sagebrush18%
- Other cover3%
- Riparian1%
Cover classes from the USGS National Land Cover Database, split into elevation bands. “Other cover” is the remainder of the classification — bare ground, water, agriculture and developed land — and is left unnamed rather than guessed at.
Land & access
About 75% of GMU 521 is public land a hunter can count on — National Forest and BLM.
- National Forest68%
- BLM8%
- Unclassified ownership<1%
- Private25%
Where mule deer live in the unit
Colorado Parks & Wildlife maps mule deer seasonal ranges statewide. This is how much of GMU 521 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 Range15%used in winter
- Winter Concentration8%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 |
| 2nd Rifle | October 24 – November 1 | Buck |
| 3rd Rifle | November 7 – November 15 | Buck |
| 4th Rifle | November 18 – November 22 | Buck |
| Private-land only | August 15 – November 15 | Either-sex, 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 68°F, lows around 42°F (mid-elevation normals)
- October — highs around 56°F, lows around 32°F, about 2.2 in of snow (mid-elevation normals)
- November — highs around 44°F, lows around 21°F, about 8.6 in of snow (mid-elevation normals)
GMU 521 mule deer hunting FAQ
Can an applicant with no preference points draw a public buck season here?
Yes. The easiest unit-wide public buck code draws reliably at zero preference points in the primary draw, making this a realistic option for applicants without points. Those below the zero-point tier sometimes also draw through the primary draw, and the secondary draw in June and leftover list afterward provide additional opportunities outside the primary system.
Which season is best for an early fall hunt on public land?
Archery and muzzleloader both run in September when temperatures are mild (highs near 68 degrees) and deer are in the velvet shed phase. Archery runs September 2–30 and muzzleloader September 12–20, offering the longest window and warmest conditions of the public seasons.
How much ground can a public-land hunter actually hunt here?
Approximately 75 percent of the unit, or about 382 square miles, is open to public hunting on National Forest and BLM lands. Access depends on specific roads, trailheads, and seasonal restrictions, which vary by location.
Is this a steep unit, or can someone hunt it on foot?
The unit is rolling to moderately steep overall, with 35 percent gentle slopes and 45 percent moderate slopes balanced against 20 percent steep or rugged terrain. Most of the unit is negotiable on foot, though hunters should be prepared for elevation gain and varied terrain depending on location.
What should a hunter expect in November compared to September?
November is significantly colder and wetter than September. Average November highs drop to 44 degrees from September's 68 degrees, and monthly snowfall increases to 8.6 inches from nearly zero in September. By late November, hunters should expect winter conditions and be prepared for snow travel.
Does this unit draw quickly, or is it competitive?
The draw is easy with low hunter pressure. The easiest unit-wide buck code draws reliably at zero preference points, and applicants often draw without any points accumulated. This is one of the least competitive hunt codes in Colorado for resident applicants.
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
- USGS / MRLC — National Land Cover Database — habitat and cover classes by elevation band
- 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
- USGS PAD-US — Protected Areas Database of the United States — land ownership and access
- Daymet daily climate, 1991–2020 (Oak Ridge National Laboratory) — 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 September 24, 2026.