Sul Ross State University

Differential Influence of Weather on Pronghorn Populations
in the Trans-Pecos Region of Texas

by David C. Simpson, Louis A. Harveson and Clay Brewer

Pronghorn (Antelocapra americana) are one of the most valuable and aesthetically pleasing wildlife resources native to the Trans-Pecos region of Texas. During the period since 1978, Texas Parks and Wildlife Department (TPWD) biologists have collected aerial survey data on Pronghorn antelope populations in this region.

Sharp trends of growth and decline are apparent in the data. These trends seem to follow periods of drought and moisture.

We will use this data to compare the correlation and regression values of simple precipitation indices and the various Palmer drought indices. We hypothesize that the more comprehensive Palmer drought indices would be more highly correlated with changes in antelope abundance than raw precipitation alone.

The final analyses will be conducted using time series regression tests and simple correlation tests. Preliminary analysis using simple linear regression to compare raw precipitation data with Pronghorn abundance data showed no significant regression (Sig. =.066, R2=.152, á=0.05). Preliminary analysis using simple linear regression to compare the Palmer drought severity index with Pronghorn abundance data showed a highly significant regression (Sig. =.000, R2=.830, á=0.05).

Further analysis seems likely to support a stronger relationship between more comprehensive precipitation indices and Pronghorn numbers than between raw precipitation data and Pronghorn numbers. The analyses provided by this study will help support further research in this area regarding Pronghorn herd management unit alignment and land use and cover data.

 Cooperative funding provided by Texas Parks and Wildlife Department and Sul Ross State University.