GMU 43B Unit 43B — Yuma
Desert bighorn on the ranges above Yuma — but most of the sheep country sits inside the Army's Yuma Proving Ground.
Lower Colorado / Gila desert — Yuma Proving Ground (BLM & military) · Last reviewed 2026-07-12
Area
862
sq mi
Public land
85%
approx.
Elevation
150–2,400
feet
Motorized
limited
access
Overview
Unit 43B lies in the low desert east and northeast of Yuma, bounded by the Colorado River to the west and the Gila River to the south. A large share of the unit falls within the U.S. Army's Yuma Proving Ground (YPG), and most of the unit's desert bighorn habitat — including the Muggins Mountains and surrounding ranges — is on YPG land where access is restricted and requires a separate military permit and safety briefing. Desert bighorn is the marquee species; a sparse desert mule deer population rounds out the opportunity.
Terrain
Hot, low Sonoran desert: river bottoms and broad creosote flats rising into small, sharply eroded desert ranges such as the Muggins Mountains, cut by sandy washes.
Cover: Riparian cottonwood-willow and saltcedar along the Colorado and Gila rivers; creosote-bursage, ironwood, palo verde, ocotillo and cholla across the bajadas; bare volcanic rock on the peaks.
Landmarks: Muggins Mountains · Colorado River (west boundary) · Gila River (south boundary) · Yuma Proving Ground · Laguna/Gila Mountains (nearby)
Access
Access is the defining challenge: much of the unit — and most of the bighorn habitat — lies inside Yuma Proving Ground, which is largely restricted or closed to public entry. YPG runs a limited hunt-access program, and sheep hunters must contact the proving ground for a safety briefing and a YPG permit before hunting there. Off-post, BLM desert is open; irrigated river-bottom farmland is private, and State Trust parcels need an Arizona State Land recreation permit. Live-fire and impact areas are absolutely off-limits.
Managers: U.S. Army Yuma Proving Ground (restricted access), BLM, AZ State Trust, Private (river-bottom farms)
Access points: US-95 north from Yuma (YPG main gate corridor) · I-8 / Gila River corridor to the south · BLM desert roads off US-95 · YPG-designated hunt access points (permit required)
Species notes
Bighorn Sheep
limited trophyDesert bighorn are the unit's marquee tag, but most sheep hold on Yuma Proving Ground ground where a separate YPG permit and safety briefing are mandatory. Success on drawn tags is high; the logistics are the hard part.
- →Contact Yuma Proving Ground first — arrange the safety briefing and access permit before the hunt
- →Glass the rocky ridgelines, saddles and cliffs of the Muggins Mountains
- →Hunt on foot; work water and shaded faces in the heat
- →Stay strictly clear of impact and live-fire areas
Mule Deer
limited opportunityDesert mule deer occur at low density, tied to the Colorado and Gila river bottoms and the wash systems. Success is modest (low-20s percent) — a water-focused spot-and-stalk hunt.
- →Hunt the green river-bottom edges and mesquite washes where deer water
- →Glass bajadas and wash mouths at first light
- →Prioritize the riparian-to-desert transition
- →Verify whether your target ground is on- or off-YPG before planning
Pro tips
- →Start with Yuma Proving Ground — no YPG permit and safety briefing means no legal access to most of the sheep country.
- →Know exactly where the YPG boundary and impact areas are before you set foot in the field.
- →Anchor deer hunting to the Colorado and Gila river bottoms and their washes.
- →Overprepare for heat and water — this is some of the hottest, driest ground in the state.
- →State Trust parcels require an Arizona State Land recreation permit.
Watch out for
- !Most of the unit and its bighorn habitat is on Yuma Proving Ground — restricted, requiring a separate YPG permit and safety briefing.
- !Live-fire ranges and impact areas are strictly closed and dangerous — stay out.
- !Extreme heat and near-total lack of water away from the rivers.
- !Private irrigated farmland along the Colorado and Gila rivers.
- !State Trust parcels require an Arizona State Land recreation permit.
- !Primitive desert roads — 4WD, recovery gear and navigation required.
Logistics
Yuma is the hub for everything — fuel, lodging, supplies. Any hunt touching Yuma Proving Ground requires advance coordination with the base (permit + safety briefing), so plan well ahead. Off-post, expect dispersed BLM camping in hot, water-scarce desert; carry ample water, extra fuel, recovery gear and navigation.
Nearest towns: Yuma, Wellton, Fortuna Foothills, Dome Valley
Seasons & regulations
This page carries no season dates or regulations. Get current rules from the official Arizona sources:
Research sources: AZGFD GMU 43B · Yuma Proving Ground (U.S. Army) · Muggins Mountains (Wikipedia)
FAQ
- How big is GMU 43B in Arizona?
- GMU 43B (Unit 43B — Yuma) covers about 862 square miles, ranging from roughly 150 to 2,400 feet in elevation. Area is computed from the unit boundary polygon.
- How much public land is in GMU 43B?
- Approximately 85% of the unit is public land. Primary managers: U.S. Army Yuma Proving Ground (restricted access), BLM, AZ State Trust, Private (river-bottom farms). Always verify ownership boundaries on the ground.
- What species does the catalog list for GMU 43B?
- Bighorn Sheep, Mule Deer. For seasons, tags, and regulations, use the official Arizona agency resources linked on this page — this page carries no regulatory information.
Put GMU 43B on your map.
Boundary lines, public/private ownership, topo, and offline maps for this unit — in Baseline Maps, free for 14 days.