CHEYENNE -- The Fortification Creek elk herd roams the isolated sage brush country and steep rocky breaks of the Powder River Basin. The herd is prized by hunters for its trophy class bulls. The herd also lives in a region ripe for coalbed natural gas development.

Given the confluence of pressures, government wildlife officials have joined with the University of Wyoming and energy companies for a $500,000 study aimed at figuring out how much energy development the elk can tolerate. Biologists recently collared 39 of the animals to monitor their behavior over the next four years.

"The area has been leased for quite some time, but the extent of the development has now gotten to the Fortification Creek area," said Chris Hanson, manager of BLM's Buffalo Field Office. "Given the nature of the resources there, and the key issue being elk, we thought it would be a good time to take a look at the cause and effects of oil and gas development on elk."

The elk herd, which was transplanted from the Yellowstone area in the 1950s, lives on about 100,000 acres near the junction of Campbell, Sheridan and Johnson counties. The region includes BLM, private and state lands, said Tom Bills, environmental coordinator for the BLM's Buffalo office.

At 240 head, the Fortification Creek herd is relatively small. Wyoming is home to an estimated 102,280 elk in total; the largest herd is the 12,770-head Jackson herd, according to the Wyoming Game and Fish Department's 2006 estimates.

Bills said the elk study is related to the BLM's new resource management plan for the Fortification Creek area. The study will examine how the components of energy development, including roads, noise and water usage, affect elk habitat.

The collars contain GPS trackers, which will enable biologists to pinpoint the elks' location every five hours. An earlier study of the same herd showed that the animals tended to avoid going within a half-mile of roads and 1.7 miles of well sites, Bills said.

"We expect the elk to react in that manner, but the collars help us monitor that," he said. "The idea is hopefully we can design methane projects to reduce those impacts. That's the ultimate goal: Can we develop coalbed natural gas in a way that we're not impacting the elk?"

The energy industry is contributing to the study. Anadarko Petroleum purchased the elk collars, Marathon/Penasco paid for the capture operation and Petro-Canada provided some funding for the data collection.

Bills said the BLM is considering a phased approach to drilling the area, developing the region one third at a time.

Jeff Beck, UW's principal investigator for the study, said it will be interesting to monitor whether the elk return to a production area after the initial construction is complete. He said the study should enable biologists to identify the factors, such as noise, dust and equipment, that drive elk away from an area.

"If we learn that, then we can provide information on mitigation that could be used to offset impacts in other places or develop gas fields that aren't impacting animals as much," he said.

Bills said the BLM has predicted that unchecked energy development would eventually drive the Fortification Creek herd into a 12,000-acre wilderness area, which could probably sustain about 50 elk.