This project’s main goals are to assess the effects of grazing by feral horses and livestock on Greater Sage-grouse demography and habitats. The Sheldon-Hart Mountain National Wildlife Refuge Complex and adjacent lands managed by the Bureau of Land Management provide the unique opportunity to assess sage-grouse populations free of feral horses and livestock grazing, populations that only have feral horses, as well as populations that coincide with both livestock grazing and feral horses.
The project team will:
- Use historical sage-grouse data collected from Hart Mountain before and immediately after livestock were removed in the early 1990s, and historical data from Sheldon before the irruption of feral horses in the mid 2000s.
- Add data from Hart Mountain (no nonnative ungulates for 20 years), Sheldon (no livestock but substantial feral horse impacts), and BLM land south of Sheldon NWR (grazed by both feral horses and livestock).
One Year Project Update
Preliminary results suggest adult survival, nest success, and chick survival rates are all lower for populations in areas that contain feral horses and livestock grazing. The researchers have observed higher nest success at nests with higher grass height and more sage-brush cover. Following a successful nest, the team has observed higher chick survival for chicks whose mothers brood them in areas with higher sagebrush cover. Further, they have observed lower values for these key habitat features in areas with high concentrations of feral horses and/or livestock.
Together, these observations suggest that uncontrolled grazing, either by feral horses or livestock may be indirectly affecting sage-grouse population dynamics. The team is currently working to map livestock and feral horse habitat use to compare to sage-grouse use in similar areas, and to create and apply modern analytical methods to identify the ecological mechanisms affecting sage-grouse demographics, and preparing for the last field season in 2016.
To date, this project has radio-collared more than 500 sage-grouse, and when combined with a historic dataset collected by Dr. Mike Gregg, this will be one of the largest datasets ever collected for this species. The results from the current work will help to identify areas of concern, identify key life history stages of sage-grouse to target for management, and guide future conservation actions geared at minimizing any negative effects of grazing and feral horses on sage-grouse.
Project start date: 1/1/2015
Fiscal year funded: 2014
Project status: Active
Project managers: Dr. James Sedinger, University of Nevada Reno