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Texas grant aids study of unexplained pronghorn decline

From the Texas Parks and Wildlife Department

-- In an effort to investigate an alarming and unexplained decline of pronghorn in far West Texas, the Texas Parks and Wildlife Department has awarded a 3-year $111,210 grant to the Borderlands Research Institute for Natural Resource Management at Sul Ross State University in Alpine.

The goal of the project is to identify possible causes for the declining pronghorn herds and to evaluate two competing hypothesis regarding pronghorn survival and productivity.

In the desert Southwest, pronghorn populations ebb and flow with rainfall. Pronghorn numbers across the Trans-Pecos have dwindled since the  1990s' drought. Once the drought broke, pronghorn and other wildlife populations began to respond with increased reproduction and survival.

However, during the past three years when rainfall provided adequate habitat, pronghorn populations have plummeted. In 2010 pronghorn population estimates in the Trans-Pecos are the lowest since the 1970s with an estimated 4,713 pronghorn across the region.

The first phase of the study is to evaluate the role of gastrointestinal parasites in pronghorn.  Based on sampling efforts in 2009, researchers documented 95 percent occurrence of parasitic round worm (Haemonchus contortus) in hunter-harvested pronghorn.  In addition, some of the pronghorn had more than 4,000 individual worms in their stomach.

High loads of roundworms can cause anemia in pronghorn, making them weak or even resulting in death. The study will help biologists better understand the relationship between pronghorn and their parasite loads.

The research team will be coordinating a large-scale effort to obtain stomach, blood, and tissue samples from all harvested pronghorn across the Trans-Pecos during the 9-day hunting season that runs from Oct. 2 to 10. Efforts will also be made to obtain samples from the Texas Panhandle, New Mexico and Arizona.

The second phase of the study will monitor causes of pronghorn fawn mortality.  Predation can be significant in pronghorn populations, especially fawns.  Beginning in spring 2011, researchers will monitor fawn productivity and survival across four core study sites in the Trans-Pecos. By monitoring fawns, researchers will assess predation and survival, and biologists seek to determine if predated fawns have high loads of stomach worms making them more susceptible to predation.

Other funding partners for the study include various Chapters of Safari Club International from across the country including the West Texas in Midland/Odessa, Lubbock, Paso del Norte in El Paso, Southern New Mexico in Roswell, and Pittsburgh, Penn., chapters.

Shawn Gray, pronghorn and mule deer program leader, and Billy Tarrant, Trans-Pecos district leader, will make a presentation "Where have all the pronghorn gone?" Sept. 28 at 5:15 p.m. in Room 130 at the Turner Range Animal Science Center at Sul Ross.  They will provide a brief history of pronghorn, discuss population trends and outline the steps TPWD and other partners are making to identify the causative factors associated with the decline. The presentation is open to the public. 

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