Factors Influencing Survival of Aoudad, Desert Bighorn Sheep, and Mule Deer on a Co-Occupied Landscape

Daniel Wilcox, Carlos E. Gonzalez, Louis A Harveson, Justin French, Shawn Gray (TPWD), and Froylan Hernandez (TPWD)

The expansion of non-native aoudad (Ammotragus lervia) has been a cause of growing concern among wildlife managers in the Trans-Pecos region of Texas. Given their sympatry with native big game species, it is important to understand potential influences aoudad may have on the sustainability of such species as desert bighorn sheep (Ovis canadensis) and mule deer (Odocoileus hemionus). However, little is known regarding the ecological impact of aoudad in Texas ecosystems. Anecdotal reports suggest aoudad out compete native big game species for food, water, and cover as well as act as a disease reservoir on Texas landscapes. If significant overlap for resources and space are occurring among aoudad, desert bighorn and mule deer, aoudad could outcompete and outgrow native populations.

This project was developed to address this concern by investigating survival dynamics of aoudad, desert bighorn, and mule deer in the Trans-Pecos. In January 2019, we captured and collared 41 aoudad, 39 desert bighorn, and 59 mule deer with satellite collars equipped with mortality sensors. These collars allow us to monitor animal movements during the study period and investigate mortality sites to determine cause of death.

During capture we also collected blood and tissue samples for disease surveillance. With this information we can compare survival rates between species, cause-specific mortalities, and environmental and disease factors influencing these rates. Results will provide wildlife managers with essential data regarding potential ecological and disease conflicts between aoudad and native species.

Funding sources: Texas Parks and Wildlife Department, West Texas Chapter Safari Club International, San Antonio Livestock Expo, and the Borderlands Research Institute.