Craig Mountain WMA Bighorn Sheep Habitat Model

Name NR502 Exercise 7 Date

Introduction Bighorn sheep (Ovis canadensis) are present within the Craig Mountain Wildlife Management Area (Craig Mt. WMA). During the lambing season, female bighorn sheep use predominantly grass, shrub and rocky habitats. They generally stay within 1000 meters of water (lakes or perennial streams) and tend to occupy steep slopes (31-85 degrees slope). The purpose of this analysis was to identify areas that may be occupied by female bighorn sheep during the lambing season on Craig Mountain.

Methods In determining locations for potential bighorn sheep habitat across the Craig Mountain WMA, three data layers were manipulated and queried in a Geographic Information System; vegetation types from the GAP Analysis Project (30 m pixel resolution), a digital elevation model from the US Geological Survey (30 m pixel resolution), and a stream layer from Idaho Water Resources (1:100,000 scale).

The raster calculator tool in the Spatial Analyst extension of ArcGIS 9.3 (ESRI) was used to conduct the analysis. First the desirable vegetation types grass, shrub, and rock, were selected from the vegetation layer. Slope was derived from the digital elevation model and areas with slopes in the range of 31 to 85 degrees were selected. The euclidian distance from perennial streams was calculated using the distance tools in Spatial Analyst and areas within 1000 m of a perennial stream were identified. The final query combined the three habitat characteristics and identified areas that consisted of grass, shrubs, and rock; had a slope of 31-85 degrees, and fell within 1000 m of a perennial stream. The area of potentially suitable habitat for bighorn sheep was calculated by converting the pixel count (30 m resolution) that fulfilled all three selection criteria to hectares.

Results Given the above specified criteria, approximately 8400 ha are determined to be suitable habitat for female bighorn sheep during the lambing season. These areas are located on the rocky and sparsely vegetated rugged terrain near rivers and perennial tributaries on Craig Mountain (Figure 1).

Figure 1. Predicted bighorn sheep lambing habitat within the Craig Mountain WMA, Idaho