Distribution and Relative Abundance of Richardson’s Ground Squirrels, Urocitellus richardsonii, According to Soil Zones and Vegetation Height in Saskatchewan During a Drought Period

Abstract

Richardson’s Ground Squirrels (Urocitellus richardsonii) prefer to establish their burrow systems in fields with shorter vegetation and good visibility. Between 2001 and 2009, warm weather and low precipitation, creating ideal environmental conditions for this species, were common throughout Saskatchewan. We therefore hypothesized that Richardson’s Ground Squirrels would be abundant throughout the agricultural region of the province and would be relatively more abundant in fields with shorter vegetation. In May and June 2008, we selected a total of 36 study plots of 0.49 ha each in 12 randomly selected rural municipalities in the Brown, Dark Brown, Black, and Gray soil zones. Using visual counts of Richardson’s Ground Squirrels and counts of burrow entrances, we found that Richardson’s Ground Squirrels were abundant across the agricultural region of the province, but densities of Richardson’s Ground Squirrels and densities of burrow entrances were generally higher in the drier Brown soil zone than in the other soil zones. In 2009 and 2010, in a study of the effect of vegetation height on the abundance of Richardson’s Ground Squirrels in the Brown soil zone, we found that densities of burrow entrances in five study plots with vegetation ≥15 cm in height were significantly (P < 0.05) lower than densities recorded in five adjacent study plots with vegetation <15 cm in height. Our findings warrant more studies on Richardson’s Ground Squirrels inhabiting fields with short and tall vegetation to determine whether differences in population densities are due to differences in birth and death rates or immigration and emigration.