The pronghorn antelope, which coexists with natural gas wells in the Pinedale Anticline of the Upper Green River Basin of Wyoming, is proving adaptable to science-informed development, the Wildlife Conservation Society (WCS) said in its second annual report, published last week.

Mirroring earlier results, the latest data suggest that the antelope herds’ population remains strong throughout the Anticline at the current level of development. The ongoing five-year study by the WCS used input from the Wyoming Game and Fish Department and the Bureau of Land Management (BLM).

The Upper Green River Basin in western Wyoming, which includes the Pinedale Anticline, is the nation’s second largest gas field. It is also home to several species of wildlife, including pronghorn antelope, which rely on the Anticline for crucial wintering range. As before, researchers again did not detect any differences in survival rates or body mass of pronghorn captured in and among the gas fields (designated experimental animals) and those captured at sites far from petroleum activities (designated control animals).

“Although we initially predicted some potential negative impacts from habitat loss and disturbance, at this juncture none have been detected,” said WCS researcher Joel Berger. He coauthored the study with WCS scientists Kim Murray Berger and Jon Beckmann. “With appropriate actions it remains possible to responsibly manage the resources of the Upper Green River Valley.” These types of management actions would be determined in an upcoming BLM Resource Management Plan.

The second-year report indicates that antelope are not avoiding gas field areas within the Anticline; however, to date only about 3% of the surface area in the Pinedale Anticline has been disturbed. In the Jonah field, researchers detected that some animals appear to be avoiding those areas of highest-intensity development. The data were collected by fitting 50 pronghorn with global positioning system (GPS) radio collars. Researchers this year deployed 100 VHF radio collars to expand the scope of their study for the remaining three years.

The GPS tracking system also showed that pronghorns rely disproportionately on specific parcels of federal and state land that facilitate major movements between summer and winter ranges, and several of these parcels are within development areas. Gas field development in some areas of the Upper Green River Basin may have little impact on the animals, but development in other areas may hinder pronghorn movements or limit pronghorn numbers.

The five-year study is voluntarily funded by Ultra Resources and Shell Exploration & Production Co. in cooperation with Questar Market Resources.

“Balancing resources in the Pinedale Anticline requires a collaborative effort,” said Shell’s J.R. Justus. “We realize that by investing in wildlife studies, such as this antelope research, we can better understand how to protect wildlife and maintain high standards for energy development.”

Ultra’s Bill Picquet added that the Pinedale Anticline operators “are committed to developing this gas field in an environmentally responsible manner. Reliable data from WCS at the end of the five-year study will be invaluable to show us how we can continue to sustain the pronghorn antelope and other wildlife in the area.”

The next three years of research will evaluate the relationship between development location and movement of antelope herds. The second annual report is now available to the public and can be accessed by the WCS website at or at

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