JACKSON - Antelope do not appear to be unduly stressed so far on and around the Pinedale Anticline, but increased energy activity may change their use of the area, according to recent results of an ongoing study.

The Wildlife Conservation Society completed its second year of a five-year study on antelope in the Upper Green River Basin, focusing on the Pinedale Anticline.

Scientists collared 50 antelope and documented movements. They discovered that antelope do not use all habitat in the development area uniformly.

"For instance, antelope rely disproportionately on habitat within the core development areas proposed by the (Bureau of Land Management) relative to outlying areas, and depend on specific parcels of federal and state land to facilitate major movements between summer and winter ranges," the report said. "Thus, gas field development in some portions of the (Upper Green River Basin) may have little impact on antelope, whereas development in other areas may hinder antelope movements or limit the region's ability to support the population objective set by the (Wyoming Game and Fish Department)."

The report says antelope are not avoiding the gas fields within the Anticline, but only about 3 percent of the surface area has been disturbed. It is estimated about 40 percent of habitat in the core development areas will be disturbed during energy exploration.

The research also showed that antelope rely on specific parcels of federal and state land for migration, and several of those parcels are in areas slated for development.

"Thus, gas field development in some areas of the Upper Green River Basin may have little impact on the animals, whereas development in other areas may hinder antelope movements or limit antelope numbers," the report said.

It was written by scientists Joel Berger, Kim Murray Berger and Jon Beckmann.

There is also an ongoing five-year study on the impacts of energy development on sage grouse and mule deer. Both those animals appear to be far more affected by energy development than antelope, although why antelope are more adaptable is unclear.

Leigh Work with Wildlife Conservation Society said the group is interested to see the point at which habitat fragmentation in developed areas affects antelope.

If habitat in the core development area is pinched in winter, it could result in a reduction in antelope numbers, the report said. That reduction will also depend on other factors, including the pace and extent of development, efforts at habitat restoration and mitigation, and severity of winters.

But, "in the absence of severe drought or winter weather, it is unlikely that the current scale of development would result in measurable impacts on antelope."

The report said animals in the control area away from development were not healthier than animals using habitat in the developed areas. In fact, antelope in the control areas had slightly higher stress levels, which may be due to poorer quality of forage.

Fences and volume and timing of traffic on roads also affected antelope's use of habitat.

"Fences seemed to have a greater effect on foraging rates than roads," the report said. "Fences, many of which predate development, and increasing vehicular traffic affect antelope foraging with effects being strongest on the smallest groups." Those smaller groups of fewer than 16 animals will likely be more disturbed unless they merge into larger groups, leave crucial winter range or habituate.

Snow also appears to be a limiting factor for antelope, as researchers found the animals avoided areas with more than about 19 centimeters of snow, and used areas with less than 12 centimeters.

The Berger team, along with Steve Cain of Grand Teton National Park, previously published a report saying the antelope migration in the Upper Green is "invariant," meaning it doesn't change from year to year. That means doing something to protect it - namely, designating a "national wildlife corridor" that would be off-limits to development, as some are pushing for - would mean working with a known quantity.

The antelope route is the second-longest migration route in the Western Hemisphere - second only to the caribou migration in the Arctic. It is estimated to be 6,000 years old.

The report used information from the BLM and Wyoming Game and Fish. It is funded by Ultra Resources and Shell Exploration & Production Co., in cooperation with Questar Market Resources, and is designed to give land managers information on how to balance natural resources with energy development.

Steven Hall, spokesman for the BLM, said the agency will work closely with Game and Fish on issues that affect antelope.

"We'll review the study and see what impact it may have on public land management," he said.

Environmental reporter Whitney Royster can be reached at (307) 734-0260 or at royster@tribcsp.com.