Relationship between habitat characteristics and densities of southern Idaho ground squirrels

Abstract

Many wildlife species living in sagebrush-steppe habitats of the Intermountain West of the United States have experienced population declines. Effective management of such species, especially restoration efforts, is contingent on understanding relationships between habitat characteristics and population densities of the target species. Unfortunately, even such basic information is often lacking. The goal of this 2-year study was to determine the relationship between southern Idaho ground squirrel (Urocitellus endemicus) population densities and habitat variables: soils (texture), topography (slope, aspect), and vegetation (canopy cover, species diversity). We measured population density indirectly through burrow entrance counts and categorized them into high-burrow and low-burrow densities. We used logistic regression and Akaike's Information Criterion to identify a best subset of models. We employed model averaging and calculated odds ratios for averaged parameter estimates found in the best models. A high density of burrows was associated with greater percentages of silt; east-facing aspects; greater plant species diversity; and greater cover of perennial grasses, perennial grasses and forbs, and native perennial forbs. Low burrow density was associated with greater percentages of sand; south-facing aspects; greater cover of exotic annuals; and lesser plant species diversity. Management of southern Idaho ground squirrel habitat should focus on protecting areas with existing native vegetation and restoring native, perennial vegetation in areas that are infested with exotic annuals, especially in areas possessing suitable soil types and topographic features. © 2013 The Wildlife Society.