Range-wide Connectivity of Greater Sage-Grouse Populations

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 A male greater sage grouse
A male greater sage grouse

The range-wide distribution of greater sage-grouse mainly consists of a few large core populations surrounded by numerous small populations. The viability of many of these small populations may be sustained by dispersing individuals from neighboring populations. Development that causes habitat loss or creates barriers to dispersal between core areas has the potential to restrict movements important to maintain genetic diversity, augment small populations, or recolonize extirpated populations. State and federal agencies are currently focusing management actions for greater sage-grouse in core areas containing the highest densities of breeding birds. The core-area approach was developed to focus limited resources in areas that will have the greatest potential to benefit the largest proportion of sage-grouse. However, the concept of focusing sage-grouse conservation in these core areas could have unintended consequences by fragmenting sagebrush habitat and increasing isolation of individual sage-grouse populations, which in turn can put genetic viability and population persistence at risk.

Habitat and population fragmentation were two of the top factors contributing to the recent U.S. Fish and Wildlife Service decision that listing greater sage-grouse was warranted but precluded. The Western Association of Fish and Wildlife Agencies, U.S. Forest Service, Bureau of Land Management, Natural Resources Conservation Service (through its Sage-Grouse Initiative), University of Montana, and USGS have begun a collaborative effort to examine gene flow and connectivity among greater sage-grouse populations range-wide. More than 5,000 currently mapped breeding locations throughout their range (11 states and 2 Canadian provinces) are visited each year for population monitoring, providing the opportunity to collect feather samples for use in this study. Researchers will collect fine-scale genetic data from these feathers and combine these data with spatial analyses of landscape components such as habitat, elevation, roads, and energy development.

Study results will provide information on levels of population connectivity as well as characteristics of barriers to dispersal and genetic exchange, including geographic distance, topographic features, and human activities and land uses. Ultimately, the spatial and temporal dynamics of colonization derived from the study—based on rate of genetic exchange and barriers to dispersal—can inform estimates of population viability relative to population isolation and risk of extirpation. Managers will be able to apply this new information towards conservation efforts in areas that will most benefit genetic exchange among greater sage-grouse populations, thereby supporting species persistence.