Scientific Study Shows Mule Deer Avoid Areas with Significant Natural Gas Development
A study funded by
Questar Exploration and Production Company, BLM and the Wyoming Game and
Fish Department shows that natural gas development is affecting population
size and the distribution patterns of wintering mule deer in the Upper
Green River Valley in Wyoming. The study, which is to continue through
2007, is being conducted by Western Ecosystems Technology, Inc.
Western
EcoSystems Technology 
Sublette
Mule Deer Study (Phase II): Long-term monitoring plan to assess potential
impacts of energy development on mule deer in the Pinedale Anticline Project
Area, 2004 Annual Report 
(5.5mb)
Western
EcoSystems Technology
Sublette
Mule Deer Study (Phase II): Long-term monitoring plan to assess potential
impacts of energy development on mule deer in the Pinedale Anticline Project
Area, 2005 Annual Report
(4.7mb)
Bounded by the Wind
River, Gros Ventre, and Wyoming Ranges, the Upper Green River Valley harbors
some of the continent’s most spectacular wildlife populations and
also holds vast deposits of natural gas. Oil and gas development so thoroughly
dominate the region that more than 75 percent of BLM’s 1.2 million-acre
Pinedale Resource Area is under lease, and the agency’s new management
plan is expected to allow at least 10,000 new wells in the next 10 to15
years -- over three times the number of existing wells.
Summarizing the
2004 annual report on the multi-year mule deer study:
- Mule deer tend to avoid areas close to well pads and associated access roads.
- Changes in mule deer distribution appeared immediately following initiation of development in the region, and no evidence of acclimation by deer to gas well pads was observed. Rather, as development progressed, mule deer selected areas farther away from the development field.
- Mule deer continue to use the Trapper’s Point bottleneck when migrating between summer and winter ranges.
The Sublette mule deer herd are the most migratory deer in the West, traveling 60 to 100 miles between the Pinedale area in winter to summer range in various mountain ranges rimming the Upper Green River Valley. (p. 6)
Sublette mule deer usually stick to narrow corridors when migrating to winter and summer ranges. Deer migrating along the Wind River Front travel over 50 miles using a corridor less than a mile wide. “Because several thousand mule deer rely on this migration corridor to access seasonal ranges, maintenance of the corridor should be a priority for agencies and conservation groups alike.” (p. 46)
Healthy winter range is critical to a healthy deer herd. “[The] reduction in winter range size and quality of available habitat may decrease the carrying capacity of the overall winter range. Assuming there is some energetic cost associated with the change in distribution or habitat use and that alternate winter range is not available, the potential for negative effects on mule deer survival and reproduction exists.” (p. 49)
"Results to date suggest that winter mule deer habitat selection and distribution patterns have been affected by natural gas development, specifically road networks and well pads. During the first two years of development the mule deer in our sample selected habitats with low to moderate road densities. And, during the first three years of development, mule deer selected habitats away from well pads…. We found no evidence of acclimation behavior. Rather, during three years of study, mule deer in our sample had higher probability of use in areas farther away from well pads as development progressed.” (p. 48)
The 2005 annual update found a 46 percent decline
of the herd wintering on the "Mesa" portion of the Pinedale
Anticline, where rapid development is occurring. Development might also
be associated with a decline in the over-winter fawn survival rate. By
comparison, the study has found no evidence of a corresponding decline
in the nearby control area on the Wind River Front, another vital Upper
Green winter range west of Pinedale, Wyoming, where no drilling is now
occurring.
The northern half of the Pinedale Anticline, known locally as the "Mesa,"
is among the newest and most productive gas fields in western Wyoming.
It also provides crucial winter range to some of the 32,000 mule deer
and 48,000 pronghorn that migrate to the Upper Green to survive the harsh
Wyoming winter on the valley’s rich sagebrush habitat.
