Grouse and Grazing Project: Effects of Cattle Grazing on Sage-Grouse Populations
The Challenge:
Greater sage-grouse (Centrocercus urophasianus) were once widespread within sagebrush-grassland ecosystems of western North America, but populations have declined since the mid-1960s. Sage-grouse were petitioned for listing under the Endangered Species Act, but the U.S. Fish and Wildlife Service (USFWS) concluded in 2015 that listing this species was not warranted, due in part to the comprehensive and unprecedented conservation measures that were initiated to conserve the species and its habitat. The USFWS findings indicated that the major threats to sage-grouse are habitat loss and the lack of regulatory mechanisms to prevent loss and fragmentation of habitat.
Grazing is the most extensive land use within sage-grouse habitat and the effects of livestock grazing on sage-grouse are often debated. Some people view livestock as a significant threat to sage-grouse. Others argue that livestock grazing may have a large-scale positive impact on sage-grouse because grazing may reduce fuel loads and result in fewer and smaller wildfires. No empirical data are available to assess either claim.
Our Response:
In 2012, Rangeland Center members and collaborators initiated a rigorous scientific research project to examine the effects of cattle grazing on: 1) demographic traits of greater sage-grouse; and 2) sage-grouse habitat characteristics, fuel loads and wildfire behavior. The 10-year study occurs on six sites across Idaho: Sheep Creek in the Owyhees, Brown’s Bench near Twin Falls, the foothills of Jim Sage Mountains, Big Southern Butte near Craters of the Moon National Monument, Idaho National Laboratory and the Pahsimeroi Valley.
This unprecedented study is expected to influence policy for the next 50 years in Idaho and throughout the West because it will rigorously document the relationship between grazing and sage-grouse. It is unique for a multitude of reasons including the length of the study (10 years), the number of partners involved, and because the research team is manipulating cattle grazing through a randomized, experimental study design at a landscape scale by working with real producers on the ground – something that has never been done!
Preliminary findings (updated January 2020):
Studies have shown that successful sage-grouse nests tend to have taller grass in the immediate vicinity compared to unsuccessful sage-grouse nests. Therefore, it appears that grass height correlates with the probability of nest predation.
However, prior studies have used data on a plot-level (small) scale. Preliminary results from this study show this same relationship at the plot-level scale but do not show the same pattern the pasture-level (large) scale. That is, there is not a strong relationship between when a pasture was last grazed and sage-grouse nesting success at the pasture scale. In other words, early findings in this long-term study show results at a pasture scale that do not agree with the interpretation of results at a plot-level scale.
One hypothesis for this pattern is that at a plot-level scale, grass height in a patch of shrubs may influence whether or not a sage-grouse nest is found by a predator. But at a pasture-scale, cows tend to graze in areas with fewer shrubs. Therefore, we may not see a strong link between grazing and sage-grouse nesting success at large scales. Another potential explanation is that some nest predators may be avoiding pastures where cattle are present.
Output & Outcomes:
Rangeland Center Members Involved:
- Courtney Conway – Fish and Wildlife Sciences, Idaho Cooperative Fish & Wildlife Research Unit
- Jason Karl - Forest, Rangeland, and Fire Sciences
- Karen Launchbaugh – Forest, Rangeland, and Fire Sciences
- Eva Strand – Forest, Rangeland, and Fire Sciences
Partners & Sponsors:
- David Little Livestock Range Management Endowment
- Eastern Idaho & Jim Sage Grazing Associations
- Great Basin Landscape Conservation Cooperative
- Idaho Cattle Association & the Public Lands Council
- Idaho Department of Fish & Game
- Permittees and Land Stewards: Jim Sage, Brown’s Bench, Big Butte, Sheep Creek, Pahsimeroi, and Idaho National Laboratory
- U.S. Bureau of Land Management
- U.S. Forest Service
- U.S. Geological Survey
- Western Association of Fish & Wildlife Agencies