Temporal Resource Partitioning Of Aoudad, Desert Bighorn Sheep, and Mule Deer in the Trans-Pecos Region, Texas

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

Desert bighorn sheep (Ovis canadensis), mule deer (Odocoileus hemionus), and exotic aoudad (Ammotragus lervia) inhabit the mountainous regions of the Trans-Pecos, Texas. Biologists and landowners are concerned about potential resource competition in co-occupied landscapes because of morphological and taxonomic similarities between these species. The arid region of the Chihuahuan Desert receives little rainfall, limiting the availability of water and vegetation resources, likely leading to competition. This project will investigate if these similar ungulates partition specific resources through time.

The Texas Parks and Wildlife Department deployed collars on 45 desert bighorn sheep (21 male, 24 female), 59 mule deer (34 male, 25 female, and 41 aoudad (33 male, 8 female) in the Van Horn Mountains from 2019 to 2020. We are utilizing these data to inspect cycles in resource use of each species through time, including water sources, vegetation resources, and escape cover. Specifically, we are examining cyclic patterns in an animal’s distance to water resources, vegetation greenness, and slope as they move.

Using resources on different cycles (e.g., diurnal use (during the day) vs. crepuscular (twilight hours)) may indicate temporal partitioning of those resources. We are studying these cycles through time to determine changes in resource importance and how temporal partitioning of resources changes throughout the year. This information will identify when these resources most influence movement behavior, as well as both when and how these species manage competition for them.

Funding sources: West Texas Club of the Safari Club International, San Antonio Livestock Exposition, Desert Bighorn Council, and Texas Chapter of the Wildlife Society.