Do Release Methods for Desert Bighorn Affect Habitat Utilization?

Taylor S. Daily, Carlos E. Gonzalez, Louis A. Harveson, Warren C. Conway (Texas Tech University), Froylan Hernandez (TPWD)

Desert bighorn sheep (O. c. mexicana), a recognized subspecies of bighorn sheep, are native to the deserts of the United States intermountain west and northwestern Mexico. In Texas they occur throughout the Trans-Pecos eco-region and historically were distributed throughout 16 mountain ranges. However, they were extirpated by the 1960s due to unregulated hunting, habitat loss, predation, and disease transmission from livestock.

Restoration efforts have been successfully conducted by Texas Parks and Wildlife Department to increase population numbers of resident (i.e., animals that currently populate a region of interest) desert bighorn at Black Gap Wildlife Management Area through the use of translocations. In winter 2017-2018, we radio collared and released 30 resident (8 Male, 22 Female) and 70 within-state translocated desert bighorn (36 Male, 34 Female) to Black Gap Wildlife Management Area. Of the 70 translocated, 28 (12 Male, 16 Female) were hard released (i.e., translocated animals immediately released onto landscape) and 42 (24 Male, 18 Female) soft released (i.e., released into an enclosure before into the landscape).

Preliminary results show habitat utilization is most correlated with herding behavior (R = 0.411, P = 0.001); however, herding behavior is most explained by release method (R2 = 0.222, P = 0.001), indicating an indirect relationship between release method and desert bighorn habitat utilization. Habitat utilization is influenced less by release type and more by the individuals’ tendency to socially interact in herds. Wildlife managers will be able to use these results to better manage for desert bighorn and ensure their preservation in the state of Texas.

Funding sources: West Texas Club of the Safari Club International, San Antonio Livestock Expo, and Texas Parks and Wildlife Department.