Unit 033, Nevada

Volcanic plateau and rolling sagebrush tablelands ranging from approximately 4,100 feet at the northeastern refuge boundary to 7,200 feet at Catnip Mountain. The landscape features expansive high-desert basins, lava-rimmed escarpments, rimrock outcrops, narrow gorges, geothermal springs, and scattered terminal lakes. Elevation changes are generally moderate except along canyon rims and the higher ridges.

Unit 033 is federally managed as the Sheldon National Wildlife Refuge (USFWS); roughly 99% of the unit is public land. Nevada State Route 140 is the only paved road within the unit, crossing east-west; Denio Junction lies approximately 14 miles east of the eastern boundary. Refuge headquarters is at Virgin Valley (44290 Virgin Valley Road, Denio NV 89404; 775-941-0199). County Road 8A and County Roads 34/34A are graded gravel routes crossing the refuge roughly east-west; a network of primitive two-track roads provides interior access. Road 8A connects westward to California SR 299 near Cedarville/Fort Bidwell. All dirt and county roads are unmaintained in winter and may be impassable in wet conditions. Vehicles — including trucks, ATVs, motorcycles, bicycles, and game carts — are allowed only on designated routes; vehicles are not allowed off designated roads. Backcountry camping is authorized by permit only. Hunting is prohibited at Big Spring Reservoir, Catnip Reservoir, Dufurrena Ponds, and the Little Sheldon portion of the refuge. No wilderness designations exist within the unit. Nearest supplies are in Denio (NV), Cedarville (CA), Fort Bidwell (CA), or Winnemucca (NV, approximately 124 miles via US-95/SR-140). Cell service is absent across most of the refuge.

Sagebrush steppe is the dominant cover type — described as one of the few intact examples of this ecosystem remaining in the Great Basin. Secondary cover includes bitterbrush, mountain mahogany, western juniper (at lower benches and canyon rims), and isolated aspen groves near springs and higher drainages. Saltbush and playa communities occupy valley floors and around terminal lakes. Riparian corridors support willows and sedges along springs and small streams.

Pronghorn are the most abundant big game, with an estimated 3,500 animals on the refuge — one of the densest concentrations in Nevada. Mule deer occur at lower density, using the sagebrush-mountain mahogany interface and higher terrain near Catnip Mountain; bucks tend to concentrate along rimrock and sagebrush benches during the rut. California bighorn sheep are present as a self-sustaining population reintroduced around 1930; they use rimrock escarpments and cliff faces across the unit. Greater sage-grouse and chukar are present as upland game birds. Non-game wildlife includes pygmy rabbits, migratory birds, and endemic desert fish species in the spring systems.