Greater Sage Grouse on the Edge of Their Range: Leks and Surrounding Landscapes in the Dakotas

Sage grouse (Centrocercus spp.) have been declining throughout their range in the United States and Canada as well as in individual states and provinces. Sage grouse, including the combined range of both the greater sage grouse (C. urophasianus) and the Gunnison sage grouse (C. minimus), once occurred in 16 states and three Canadian provinces; now they only occur in 11 states and two Canadian provinces (Connelly and Braun 1997, Schroeder et al. 1999). Excluding states suggested as part of the Gunnison sage grouse range (Young et al. 2000), greater sage grouse range has declined from 13 states and three Canadian provinces to 11 states and two Canadian provinces (Schroeder et al. 1999). Excluding states suggested as part of the Gunnison sage grouse range (Young et al. 2000), greater sage grouse range has declined from 13 states and three Canadian provinces to 11 states and two Canadian provinces (Schroeder et al. 1999). Concerns are growing over the reasons for these declines. The habitat around active and historically active greater sage grouse leks in North Dakota and South Dakota was studied during 2001 and 2002 in an attempt to find reasons for desertion of once thriving leks and for apparent population declines. I collected information on current and historic (i.e., leks with 0-years) sage grouse lek counts and distributions in western North Dakota and South Dakota. A steady decline is evident when reviewing the entire recorded period of greater sage grouse surveys in North Dakota (1951-2002) and South Dakota (1972-2002). There is also apparent eastern edge abandonment of the active breeding range over the years. Land use patterns in these areas once occupied by greater sage grouse have likely changed and are now failing to meet their needs (Connelly and Braun 1997). I compared peripheral microhabitat and landscape characteristics to identify possible reasons for lek abandonment. For microhabitat data, I systematically selected 12 sample sites at equidistant points from each other within 1.5 km of the lek center. No differences (P > 0.10) were detected between sagebrush (Artemisia spp.) cover or sagebrush density around active leks versus that around historically active leks in North Dakota and South Dakota. Sagebrush density does appear to have a positive effect on greater sage grouse lek size in North Dakota and South Dakota. Landscape level data were recorded and assessed using satellite imagery. Comparisons were made of 1972-1976 and 1999-2000 percent tilled and non-tilled. These land use comparisons were made between current leks versus historically active leks, active leks versus random sites, and abandoned regions versus active regions. The 1999-2000 imagery illustrated that percent tilled ground, and thus fragmentation, was greater (P < 0.10) within abandoned areas than within active areas in North Dakota. However, 1972-1976 imagery revealed that this relationship has been static over the last 30 years. Thus, if the decline of sage grouse is the result of tilled ground infringements it had to occur prior to 1972. Sage grouse, a landscape species, may have been slow to show the effects of this land use change.

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