3.7.1.2 Habitat

Observations of rare, threatened, endangered, and other special status species were documented, and their spatial location was recorded as necessary (HDR 2022c).

Field observations and numerous geospatial datasets were used to conduct a desktopbased wildlife habitat assessment. Wildlife habitat modeling was conducted for all BLM Sensitive, state-listed, ESA-listed, and big game species with a potential to occur in the wildlife study area. The USFWS IPaC database was used to develop a list of species currently listed as threatened or endangered under the ESA that may occur in the Project Area (USFWS 2022a; Appendix G). This list also included a candidate species for listing, the monarch butterfly (Danaus plexippus). The current BLM Wyoming Sensitive Species List (BLM 2010) was used to identify BLM Sensitive Species. Species lists were developed using the State of Wyoming’s Natural Resource and Energy Explorer tool. The WGFD list of Tier I and Tier II Species of Greatest Conservation Need (SGCN) species (WGFD 2019a) was also included in the study. Big game species were also included based on comments from WGFD (HDR 2022c).

The first step of the desktop-based wildlife habitat assessment was to identify which species on the above lists may occur within the wildlife study area. This initial assessment relied on publicly available peer-reviewed literature and spatial datasets from the USGS and Wyoming Natural Diversity Database (WYNDD). Biologists determined that GAP landcover data would be sufficient for use in modeling wildlife habitat throughout the wildlife study area and habitat suitability index values (HSI) were assigned to each GAP landcover type on a scale from 0 to 3 (an HSI of 0 indicated Unsuitable/Non-Habitat and an HSI of 3 indicated High-quality Habitat) (HDR 2022c).

As warranted for each individual species, based on a qualitative assessment of all available data identified, researchers considered and used from one to several publicly available geospatial datasets to model relative habitat quality for each species separately. The methodology used to develop each species habitat model varied by species based on the habitat requirements, life history, and available spatial data (HDR 2022c).

When multiple datasets were used as model inputs, a multi-criterion habitat evaluation procedure was conducted to model potentially suitable habitat in the wildlife study area. Publicly available literature describing habitat requirements were used to identify the key characteristics of suitable habitat for each species assessed. These characteristics were then identified within one or more of the publicly available spatial datasets. Multiple spatial datasets (or model inputs) were summed using the Weighted Sum tool in the Spatial Analyst/Overlay toolbox in ArcGIS 10.7.1. Each model input was equally weighted because the relative importance of each species was assumed to be equivalent (HDR 2022c).

3.7.1.2 Habitat

The wildlife study area is primarily dominated by Inter-Mountain Basins Big Sagebrush Steppe and Rocky Mountain Foothill Limber Pine-Juniper Woodland (HDR 2022c). These land covers are described in Section 3.6.1. Anthropogenic disturbances in the form of past and present uses of the area (e.g., abandoned mines, roadways, utilities, fences) are commonly located within and adjacent to the wildlife study area.

The North Platte River basin generally contains sandy soils and sandy clay-loams, with gravel and rocks becoming more numerous closer to the mountains and along higher gradient streams. Mountain terrain is moderate to steep, and slopes become less steep on the adjacent foothill and plains, with a total elevation change of approximately 1,700 feet between the Seminoe Mountains and Seminoe Reservoir. Principal human uses in this watershed are livestock grazing, hay production, and recreation. Livestock use is with cattle, employing both cow/calf and yearling operations. Seasons of use are primarily winter and spring at lower elevations and summer and fall at higher elevations (BLM 2003).

Vegetation is predominantly either sagebrush-perennial grass or saline-influenced vegetation communities in the Project region. Wyoming big sagebrush (Artemisia tridentata subsp. wyomingensis) is the most common species amongst the 9 species or subspecies of sagebrush shrubs commonly occurring together or in site-specific habitats. Nuttall’s saltbush (Atriplex nuttallii) and black greasewood (Sarcobatus vermiculatus) are the distinctive species of saline-influenced communities. Mountain shrubs, which include bitterbrush (Purshia tridentata), snowberry (Symphoricarpos occidentalis), serviceberry species (Amelanchier spp.), and mountain mahogany (Cercocarpus ledifolius), occur in 10-inch or higher precipitation zones and are usually intermixed themselves or with sagebrush and aspen (Populus) (BLM 2003).

Aspen woodland is usually found above 7,000 feet in small pockets on north and eastfacing slopes where snow accumulates or there is some other source of additional moisture. Conifer woodlands occur above 7,500 feet, with limber pine (Pinus flexilis) and juniper (Juniperus scopulorum) on drier sites and lodgepole pine (Pinus contorta), subalpine fir (Abies lasiocarpa), and spruce (Picea spp) on wetter sites. Herbaceous and shrub-dominated riparian communities are the most common in the Project region, with tree-dominated habitat such as cottonwoods (Populus spp) being the least common in occurrence (BLM 2003).

Wildlife is abundant and diverse within the Project vicinity. Pronghorn antelope (Antilocapra americana), mule deer (Odocoileus hemionus) and Rocky Mountain elk (Cervus canadensis nelsoni) are common big game species, with small populations of bighorn sheep (Ovis canadensis) in the Ferris and Seminoe Mountains. Greater Sagegrouse (Centrocercus urophasianus) and mountain plover (Charadrius montanus) are important species of interest. Raptors include golden eagle (Aquila chrysaetos) and bald eagle (Haliaeetus leucocephalus); ferruginous hawk (Buteo regalis), red-tailed hawk (B. jamaicensis), Swainson’s hawk (B. swainsoni), burrowing owl (Athene cunicularia); and other hawks, harriers, and owls. Other commonly observed wildlife are coyotes (Canis latrans), badger (Taxidea taxus), beaver (Castor canadensis), muskrat (Ondatra zibethicus), white-tailed prairie dogs (Cynomys leucurus), ground squirrels (Urocitellus elegans), waterfowl, and songbirds (BLM 2003).

Based on the results of the 2021 Habitat Assessment and Rare, Threatened, and Endangered Species Evaluation Study (HDR 2022c), a total of 19 land cover and vegetation types occur in the wildlife study area. A full description of these land covers and vegetation types, as well as maps depicting the locations of these areas within the wildlife study area, are included in Section 3.6, Botanical Resources. The three dominant vegetation types occurring in the wildlife study area (described below), in decreasing order