Influence of Topography, Soils, and Vegetation on Densities and Body Condition of Southern Idaho Ground Squirrels

Publication Date


Type of Culminating Activity


Degree Title

Master of Science in Biology



Major Advisor

James C. Munger


Stephen J. Novak


Eric Yensen


Several species of ground squirrels living in sagebrush steppe habitat of the Intermountain West have experienced population declines. Chiefly among these is the southern Idaho ground squirrel (Spermophilus brunneus endemicus). Federal management projects undertaken to restore this subspecies to stable numbers have been difficult to execute because of a lack of scientific information pertaining to their habitat requirements. The goal of this study was to identify characteristics of southern Idaho ground squirrel habitat. Specifically, soils (soil texture), vegetation (canopy cover, species diversity), and topography (slope, aspect) were examined to determine how they influenced densities of southern Idaho ground squirrels. The study was conducted in 2004 and 2005 in southwestern Idaho. Logistic regression and Akaike's Information Criterion were incorporated to identify a best sub-set of models. Model averaging was employed and odds ratios calculated for averaged parameters estimates found in the best models. High densities of squirrels were associated with soils containing higher percentages of silt, east-facing aspects, and higher cover of perennial grasses, perennials, native perennial forbs, and higher species diversity. Low densities of squirrels were associated with soils containing higher percentages of sand, south-facing aspects, higher cover of exotic annuals, and lower species diversity.

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