PARENT SESSION
Poster Session #31: Animal Population and Community Ecology I.
Wednesday, August 7. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Soil characteristics related to Stephen's kangaroo rat densities.

Cummins, Kevin^*,1, Bornyasz, Margaret², Deutschman, Douglas¹, ¹ San Diego State University, San Diego, CA² University of California-Riverside, Riverside

ABSTRACT- Dipodomys stephensi (Stephen's kangaroo rat, SKR)is a federally listed endangered species. Until now, research on the habitat characteristics influencing this species' abundance has primarily focused on vegetation and large scale geographic and geologic patterns. This study investigated the influence of soil characteristics on the neighborhood density of D. stephensi . SKR density and many environmental factors, including vegetation composition and soil characteristics, were recorded at 45 plots over three years in Riverside, CA. Logistic regression and variance ratio tests demonstrate that SKR densities are strongly correlated with soil texture. Sites with high SKR densities shared similar texture characteristics suggesting individuals may be choosing specific sites based on soil texture. This pattern was strongest for lower soil horizons. In a separate set of analyses, multivariate adaptive regression splines (MARS) were used to explore the relationships between SKR, vegetation and soil characteristics. This analysis was chosen because many characteristics of soil are measured on an ordinal scale. The MARS analysis provides evidence that variation in open vegetation, soil moisture, and soil dry consistence (rigidity and brittleness) are related to SKR densities. This study is the first to demonstrate that SKR may be responding to soil characteristics on a small scale, in addition to other features of their environment.

KEY WORDS: Stephen's kangaroo rat, Dipodomys stephenis, Multivariate analysis, Adaptive regression spline