PINEDALE - The second phase of multi-agency study has again confirmed that natural gas development is affecting population size and the distribution of wintering mule deer on the Mesa portion of the Pinedale Anticline.

The study by Western Ecosystems Technology, Inc. concluded that mule deer numbers declined in the Mesa by 30 percent overall during the seven-year research project, which ran from 2000-2007.

However, mule deer numbers stabilized and then increased during the final three years of the study.

The Sublette Mule Deer Study Phase 2 Final Report released Tuesday was co-authored by Hall Sawyer, Ryan Nielson and Dale Strickland.

The study was designed to better understand potential energy-related impacts on wintering mule deer in the Pinedale Anticline gas field.

The authors said the study's results suggest that efforts to minimize direct and indirect habitat loss from future oil and gas development should focus on "technology and planning that reduce the number of well pads and the human activity associated with them."

Oil and gas industry officials said the study documents the increasing winter use of the Pinedale Anticline by mule deer over the past three years and reflects the success of the industry's ongoing mitigation efforts in the field.

"Questar is encouraged by this positive trend and believes that recent mitigation such as the installation of a liquids gathering system (LGS) and increased directional drilling have played a positive role," Diana Hoff, general manager of the Pinedale Division for Questar Exploration and Production, Inc., said in a release.

"We are also pleased to see that the migration routes of the mule deer, to and from the Mesa, are intact and functional," she added.

But conservationists said the report shows there's still a need for fewer well pads and less human disturbance on the Mesa, especially during winter.

"(The study) documented a 30 percent decline in mule deer over seven years. … By any scientific standards, this is hugely significant," said Linda Baker with the Upper Green River Valley Coalition.

"The health of our wildlife will depend on reducing the number of well pads and wintertime human disturbance in the field, especially because (the study showed) winter drill pads were avoided the most" by mule deer, Baker said in an e-mail.

The study said from 2001-2004 there was an approximately 46 percent decline in mule deer numbers on the Mesa, which was attributed in part to oil and gas activity.

"Data collected from the Mesa indicated that mule deer numbers declined during the first four years of gas development and increased the following three years, for an overall decline of 30 percent," the study said.

"During the same time period, the Wyoming Game and Fish Department estimated a 10 percent decline for the larger Sublette herd unit, which included the Mesa and several other winter ranges," the report continued. "We conclude that mule deer numbers declined in the Mesa and there is no evidence that suggests other segments of the Sublette mule deer population declined at a comparable rate."

Contact southwest Wyoming bureau reporter Jeff Gearino at 307-875-5359 or gearino@tribcsp.com.

The Sublette Mule Deer Study Phase 2 Final Report can be viewed on Western Ecosystem Technology, Inc.'s Web site at http://www.west-inc.com/big_game_reports.php]]->