Modeling Translocation Strategies for Pronghorn Populations in the Trans-Pecos, Texas

Philip Boyd, Patricia Moody Harveson, Louis A. Harveson, Whitney Gann, and Shawn Gray (TPWD)

In 2011, Texas Parks and Wildlife Department (TPWD) and the Borderlands Research Institute began an effort to boost pronghorn populations (Antilocapra americana) in the Trans-Pecos region of Texas. Restoration efforts included translocating groups of pronghorn from the Texas Panhandle. A decrease from approximately 17,000 pronghorn in the 1980s to a low of approximately 3,000 in 2012 led to the initiation of translocation efforts.

Habitat fragmentation in the Trans-Pecos has led to metapopulation arrangements, which TPWD manages as 11 unique units, known as meta units. This study sought to evaluate the effectiveness of various strategies in restoring regional pronghorn populations to a targeted population of 10,000 and estimated the probability of meta unit population quasi-extinction, and meta unit population extinction over a 20-year period.

We built a stage-based simulation model using TPWD survey data and survival data from recent studies. There were 13 different iterations of the model that each tested a unique translocation scenario. The models illustrate that sustained translocation strategies can increase pronghorn populations in the Trans-Pecos beyond the additive increases contributed by each translocation, though the goal of 10,000 pronghorn was not consistently reached across every tested scenario.

The most successful translocation strategy modeled involved translocating 1,000 pronghorn over 10 years to Trans-Pecos meta units that historically showed the most sustained success and were closest to their targeted population goal when a release site was chosen for each translocation year.

Funding source: Texas Parks and Wildlife Department.