Unit 63, Idaho

The unit is predominantly flat to gently rolling sagebrush-steppe terrain typical of the eastern Snake River Plain, a volcanic plateau shaped by ancient lava flows and alluvial deposits. Elevations range from approximately 4,793 feet at low points to roughly 5,950 feet at higher benchmarks, with very limited topographic relief. Scattered lava fields, dry lake beds, marshes (notably around Mud Lake Wildlife Management Area), and irrigated crop ground intersperse the rangeland. There are no mountain ranges within the unit itself; higher terrain of the Lemhi Range and Bitterroot Mountains lies well outside its boundaries.

Land ownership: U.S. Department of Energy / Idaho National Laboratory (INL) — 35.6%; private agricultural land — 35.6%; Bureau of Land Management (Upper Snake Field Office, Idaho Falls District) — 20.9%; State of Idaho — 7.5%; other/NWR/military — ~0.5%. There are no National Forest, wilderness, or Access Yes! properties in the unit. Primary highway corridors: Interstate 15 (Blackfoot to Dubois), U.S. Highway 20/26, State Highway 22, and U.S. Highway 26. INL lands require a separate annual INL Hunting Pass (available at the Upper Snake Regional Office, 4279 Commerce Circle, Idaho Falls, 208-525-7290, or by email request), annual UXO (unexploded ordnance) safety certification, check-in/out by phone to the INL number on the permit, and are open only for elk and pronghorn hunting (tags for Units 63, 58, and 51). Motorized access on INL is limited to established two-track roads shown on the permit map; hunters must wear at least 36 sq in of hunter orange above the waist and carry cell phones. The INL huntable area expanded by 80 square miles in 2025. Camas National Wildlife Refuge within the unit is closed to all hunting.

Vegetation is dominated by sagebrush steppe — primarily Wyoming big sagebrush, basin big sagebrush, and mountain sagebrush — with an understory of bluebunch wheatgrass, Idaho fescue, Indian ricegrass, rabbitbrush, and fourwing saltbush. Approximately 60 percent of the landscape is classified as rangeland. Irrigated crop fields (about 21 percent of the unit) and gravity-flow irrigated farmground (roughly 8 percent) provide important forage and cover for elk, deer, and pronghorn. Riparian willows and wetland marshes occur around Mud Lake and Camas National Wildlife Refuge (closed to hunting). Scattered juniper woodlands exist on INL grounds.

Elk use Unit 63 as both a year-round residential range and a winter range. IDFG GPS-collar research (initiated 2024, 15 elk collared July 2024 on INL) is ongoing; biologists suspect the unit supports two elk groups — year-round residents and seasonal migrants that winter in Unit 63 but summer in adjacent higher-elevation units. Final movement data is still being collected. Elk congregate heavily on irrigated private agricultural fields, creating significant crop-depredation conflicts that drove the unit's removal from the general Snake River Zone elk tag in 2019. Mule deer are resident throughout the sagebrush uplands and crop edges. Pronghorn occupy the northern portion of the unit (north of State Highway 33), particularly near crop fields. Black bear and mountain lion are present at low densities. Gray wolf packs have been documented in the unit. Shiras moose occur at low numbers. The Mud Lake WMA and Camas NWR provide important wetland stopover for migratory waterfowl and sandhill cranes. Sage-grouse, sharp-tailed grouse, and pheasant are present in appropriate habitat patches. Raptors — ferruginous hawk, short-eared owl, prairie falcon — are common on INL sagebrush steppe.