GIS-based Habitat Models for Bighorn Sheep Winter Range in Glacier National Park, Montana

I used logistic regression to construct bighorn sheep winter range habitat models for 2 study areas in Glacier National Park (GNP), Montana. During 2 winters, habitat use was described through systematic ground surveys supplemented with focal observations, lasting 1-3 days, of recognizable individual sheep. Available habitat was evaluated using 12 habitat parameters, each measured at a 30-by-30 meter grid-cell resolution with GIS software. For each study area, a set of candidate models was constructed and then validation tested at the other study area. Using habitat parameters common to the best model from each study area, I then pooled all data to construct 2 versions of a final winter range model applicable across GNP. I compared the performance of the final GNP models to that of a regional model (the Smith model GIS application). The GNP models correctly classified 75% and 38% of grid-cells with observed winter use at the 2 study areas. The Smith model GIS application correctly classified 10% and 11% of grid-cells with observed winter use at the 2 study areas. Habitat parameters in the final GNP models were distance-to-escape terrain, snow cover, solar radiation index, slope, and either land-cover type (from a classified satellite image) or horizontal visibility and 2 satellite wavelength-band reflectance values. The final models will be useful to GNP managers for identifying suitable bighorn sheep winter range potentially threatened by conifer encroachment, livestock trespass, exotic plants, and/or illegal hunting pressure.