Holloran, M. J. 2005. Greater sage-grouse (Centrocercus urophasianus) population response to natural gas field development in western Wyoming. PhD Dissertation. University of Wyoming. Laramie, Wyoming. 211pp.

Introduction	Introduction, Abstract, Table of Contents, Acknowledgements, Preface (650 KB)
Chap. 1	Greater Sage-grouse Population Response to Natural Gas Field Development in Western Wyoming: Are regional Populations Affected by Relatively Localized Disturbance? (117 KB)
Chap. 2	Greater Sage-Grouse Response to Natural Gas Field Development in Western Wyoming (1.2 MB)
Chap. 3	Natural Gas Development Impacts to Greater Sage-Grouse Populations: A Summary of Research Conducted in Western Wyoming with Thoughts on Management and Future Research Options (310 KB)
Append. A	Spatial Distribution of Greater Sage-Grouse Nests in Relatively Contiguous Sagebrush Habitats (612 KB)
Append. B	Greater Sage-Grouse Early Brood-Rearing Habitat Use and Productivity in Wyoming (689 KB)
Append. C	Greater Sage-Grouse Research in Wyoming: An Overview of Studies Conducted by the Wyoming Cooperative Fish and Wildlife Research Unit between 1994 and 2005 (2.5 MB)

   The Holloran study found:

• Populations of breeding males on leks (sage grouse mating sites) in areas subjected to full-field natural gas development in the Pinedale Anticline and Jonah fields declined by an average of 51 percent from the year prior to development to 2004, compared to only a 3 percent decline at undisturbed leks.



• Males at three leks surrounded by natural gas development declined by 89 percent; two of the three leks were abandoned entirely within 3 to 4 years of initiation of gas drilling.



• Active drilling within 3.1 miles of a sage grouse lek reduced the number of breeding males that used the lek.



• As road traffic increased, the number of breeding males on affected leks decreased.



• As well density increased, the number of breeding males on affected leks decreased.



• Females strongly avoided nesting in areas of high well density.



• There was a 21 percent decline in the population of nesting females compared to undisturbed females over the 5 years of the study.



• Females nesting in developed areas had a significantly lower survival rate than female grouse in undeveloped areas. Although nest success rates were higher in developed areas, this increase was not sufficient to overcome the reduced female survival rates, resulting in an overall 21 percent decline in sage grouse population growth in developed gas fields compared to undeveloped areas.



• Population reductions likely result from a combination of dispersal away from gas fields and increased mortality rates for birds affected by development.



• The study's findings suggest, "current development stipulations are inadequate to maintain greater sage-grouse breeding populations in natural gas fields" (p. 57).

Of the 313 square miles of the Pinedale Anticline field, only 7.3 square miles (approximately 2 percent) is not leased for oil and gas development. The study predicted that sage grouse populations would become extinct in the Pinedale Anticline and Jonah development fields within 19 years if current population trends continue.