TAXONOMY AND DISTRIBUTION OF THE IDAHO GROUND-SQUIRREL, SPERMOPHILUS-BRUNNEUS

Spermophilus brunneus was found in isolated meadows surrounded by coniferous forests in Adams and Valley counties, Idaho, and also further south at lower elevations in the relatively xeric foothills north of the Payette River in Gem, Payette, and Washington counties. Marked differences in pelage coloration related to soil color exist between the disjunct northern and southern populations. Univariate and multivariate analyses of external, cranial, baculum, and pelage characters revealed significant sexual dimorphism in external and cranial characters and also that northern and southern S. brunneus are well-differentiated taxa. The bacula are about as distinct as those of S. townsendii idahoensis are from S. washingtoni, suggesting that the two S. brunneus may be approaching species-level differentiation. A change in soils, vegetation, and topography, but no apparent biogeographic barrier, separates the two taxa. Southern S. brunneus is described herein as a new subspecies.