This study will examine how the reorganization of a semidesert grassland caused by global climate change has influenced snake relative abundances and habitat use. We will conduct this study in northwestern margin of the Chihuahuan desert, southeastern Arizona. We will collect data and combine it with existing data (dating back to the 1950's) on the habitat associations of desert snakes and then incorporate all data into a detailed landscape-level analysis of habitat change and concomitant changes in snake distributions and relative abundances. This project is collaborative and will draw upon the complimentary talents of the PI (Dorcas), Dr. Joseph R. Mendelson (Utah State University), and three Davidson College undergraduate students. Dr. Mendelson is providing his own funding for his aspects of the project.

The earth is presently experiencing a biodiversity crisis of unknown extent and proportion. Associated with this is the reorganization of arid ecosystems around the planet. A persistent problem with our attempts to assess changes in natural populations is a glaring lack of long-term data on both the relative abundance of species in a given area and also their basic natural histories. Long-term studies of the dynamics of natural populations and the gathering of basic natural history information are critical if we hope to assess apparent changes in populations and attempt to understand their underlying causes. Our study is founded upon an existing long-term database of the snakes of the study area, which has been experiencing an ecological reorganization.

Undergraduate students from Davidson College will be heavily involved in the collection and analysis of data for this project. Standardized, nightly transects by vehicle along Portal Road and U. S. Hwy 80 (approx. 200 miles/night) will be made during the summer monsoon season (late July-early August). All snakes seen will be identified, measured, and precise locality data recorded - global positioning system (GPS) coordinates to within 2 m. Live snakes will be released at the road edge and dead snakes will be collected as voucher specimens and for dietary analysis. Relative abundance of species will be statistically compared to previously published data from the same transects in order to assess population changes in the area. Snake locations will incorporated into a geographic information system (GIS; ArcGIS 8.1) layers and remote sensing data (i.e., Landsat 7 imagery) for analysis of habitat selection.

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