Our Work

By Hailey Barton, Carlos Gonzalez, Mark Bell, Justin French, Levi Heffelfinger (TAMK), Froylan Hernandez (TPWD), Shawn Gray (TPWD)

Elephant Mountain Wildlife Management Area (WMA) serves as a nursery herd for ongoing desert bighorn (Ovis canadensis) restoration efforts in Texas, so the primary management objective is producing surplus animals for translocation. Elephant Mountain WMA also provides public hunting opportunities, particularly for mule deer (Odocoileus hemionus), so maintaining a healthy mule deer population is also a key goal.

To preserve habitat quality and mitigate competition between these species, we must first estimate the WMA’s desert bighorn capacity. Traditional methods of estimating carrying capacity aren’t conducted often because they are time-consuming, tedious, imprecise, and costly. Environmental conditions vary from year to year, causing dramatic shifts in habitat quality and changes to carrying capacity. To keep pace, we need a more efficient method to assess habitat annually.

Our objective is to use remote sensing (satellite imagery) to monitor the quality of forage. Previous studies have established a relationship between satellite vegetation indices and desert bighorn nutritional performance. We expect this relationship to be density-dependent, so we can estimate carrying capacity from satellite imagery. We hypothesize that a higher density of bighorn reflects a more gradual slope in the relationship between the Modified Soil-Adjusted Vegetation Index and fecal nitrogen. With more individuals present on the landscape, a lower quantity of high-quality forage is available, resulting in lower fecal nitrogen content.

This study will provide a framework for efficient monitoring of bighorn habitat via satellite, providing essential guidance for management.