Fluctuation in species’ distributions and space utilization are two widely studied parameters in ecological research due to their capacities to indicate variation in external influences. Investigators need to know the topographical characteristics, fluxes in range-size, and how a species’ space use compares to available space in order to detect change over time. Fossorial mammals are often in aggregations and the locations of these aggregations often remain consistent year-to-year, but the explicit boundaries of their colonies can change annually. The northern Idaho ground squirrel (Urocitellus brunneus) is an endemic species to Idaho that was federally listed as a threatened species under the Endangered Species Act in 2000. Northern Idaho ground squirrels have a limited distribution in Adams and Valley counties of Idaho and live in isolated aggregations (demes). We mapped the area occupied (colony footprint) by 5 demes of NIDGS in the summers of 2014 and 2015 to compare the footprint sizes between years, identify unifying characteristics of the geographic locations (slope, aspect, and elevation), and determine how the footprint of an aggregation compares to available meadow space.
Results/Conclusions
We documented slope, aspect, and elevation with the 5 colony footprints. The average slope of the sites was 13.5° with a range of 10.8° to 14.6°. All sites were positioned on east- to southeast-facing aspects, at elevations ranging from 1,200 to 1,650 meters. The size of the colony footprint was reduced by 33% (on average) between 2014 and 2015 (t = 4.84, p < 0.01). The percentage of meadow encompassed by the deme footprints was 49.3%, 15.1%, 34.4%, 41.3%, and 208.6% in 2014 and 31.8%, 9.6%, 29.9%, 22.2%, and 187.7% in 2015. The 33% reduction in colony footprints between years may reflect either a reduction in NIDGS distribution or difference in observer methods (the colonies were mapped by a different observer during 2014 and 2015). At one of the 5 sites, the deme footprint exceeded the meadow borders into the surrounding forest in both years.