Unit 36B, Arizona

Rugged sky-island terrain with a broad lower basin floor at roughly 3,000 ft in the Altar Valley and rolling mesquite hills, rising steeply into multiple small mountain ranges that top out at Atascosa Peak (6,440 ft — confirmed via USGS/Wikipedia; GoHunt incorrectly lists 6,200 ft). Total unit area: 561 square miles across Pima and Santa Cruz counties. GOHUNT characterizes the landscape as grasslands, ravines, and Sonoran desert at lower elevations transitioning to rugged and extremely steep hills and mountains. Four-wheel-drive or ATV access is recommended for back-country terrain.

Unit boundaries run from I-19 and US-89 in Nogales southwest along Grand Avenue to the US-Mexico border, west along the international boundary to AZ-286, north on AZ-286 to the Arivaca-Sasabe Road, southeast on Arivaca-Sasabe Road to Arivaca, then northeast on Arivaca Road back to I-19. Primary road access corridors: (1) Arivaca Road — exit I-19 at Amado/Chavez Siding, paved to Arivaca village; (2) Ruby Road (AZ-289) — exit I-19 ~8 miles north of Nogales, paved ~9 miles to Pena Blanca Lake Recreation Area, then dirt west into the Atascosa and Tumacacori Mountains; (3) Rock Corral trailhead — Tumacacori exit off I-19; (4) Peck Canyon — southern access off I-19. Public land managers: Coronado National Forest (Nogales Ranger District, 303 Old Tucson Rd, Nogales AZ; 520-761-6000) covers mountain terrain (~56% of unit); Buenos Aires National Wildlife Refuge (117,107 acres, est. 1985, Pima County) covers western Altar Valley — hunters on refuge roads must keep all firearms unloaded and cased; hunting permitted refuge-wide except in posted No Hunt Zones (~12,544 acres, ~11% of refuge, including Brown Canyon, Arivaca Management Units, headquarters area, Pronghorn Drive scenic corridor, and near residences/quail breeding facility). A border strip extending ~3/4 mile north of the international boundary (~3,500 acres) has been closed to public access since 2006 due to border security concerns. State trust land and private inholdings (~14%) also present; some low-elevation roads through private land are gated. No designated Wilderness within the unit.

Lower elevations: semidesert grassland, mesquite savanna, catclaw acacia, and Sonoran desert scrub with cholla, prickly pear, and ocotillo. Transition zones: dense ocotillo thickets and chaparral on mid-elevation slopes. Higher mountain canyons and ridges: Madrean oak woodland (Emory, Arizona white, silverleaf oak), with sycamore-lined riparian drainages. The Buenos Aires NWR core supports one of Arizona's largest surviving tracts of native sacaton and tobosa semidesert grassland. No significant ponderosa pine component at this latitude and elevation range.

Coues white-tailed deer are the unit's signature big game species, concentrated in the oak-grassland canyons of the Atascosa, Pajarito, San Luis, and Tumacacori mountains; 36B is ranked as most preferred among the Unit 36 sub-units for having the highest whitetail density and largest percentage of ideal mountain habitat. Desert mule deer occur in the lower desert hills and flatlands. Javelina are present unit-wide, most densely in mesquite-grassland areas. Pronghorn have been reintroduced on the Buenos Aires NWR in the Altar Valley grasslands (reintroduction program documented; hunting permit availability for 36B not confirmed in sources). Black bear are present in the mountain ranges. Mountain lion range throughout the unit. Mearns (Montezuma) quail are present in the oak-grass transition; Gambel quail in lower desert. Arivaca Lake and Pena Blanca Lake support largemouth bass. Feral hogs may be taken during any open hunting season without limit. Jaguar sign has been documented on the Buenos Aires NWR historically (unit borders known jaguar movement corridors from Mexico). Gould's turkey: adjacent units 35A/35B are confirmed Gould's draw units and the Atascosa/Tumacacori ranges fall within the Gould's geographic range, but Unit 36B's explicit inclusion in the Gould's draw is LOW CONFIDENCE — not confirmed in sources consulted.