The sagebrush ecosystem — a vast, dry landscape that supports hundreds of wildlife species and livelihoods in the West — is shrinking and changing. Livestock grazing is the dominant land-use across much of this ecosystem.
Today’s grazing practices are more precisely managed than in the past, and land and livestock managers need to understand how the timing and presence of cattle affect wildlife communities to more effectively manage for resilient sagebrush ecosystems that support both wildlife and rural economies.
By showing how livestock grazing season of use and changes in plant cover influence small-mammal activity and predator presence, the study can help managers make informed decisions that support rural livelihoods while conserving wildlife.
To address this need, Oregon State University researchers and Extension professionals in the College of Agricultural Sciences studied how different grazing seasons influenced rodents and their predators. From 2018 to 2021, the team conducted experiments in nine pastures at the Northern Great Basin Experimental Range in southeast Oregon.
Pastures were assigned to one of three treatments: no grazing, dormant season grazing (in fall or winter), or rotational grazing — spring one year followed by summer the next.
The team used motion-triggered trail cameras and walking surveys to monitor small mammals such as mice, chipmunks, ground squirrels, kangaroo rats and rabbits, along with meso-predators including badgers, coyotes and bobcats. They also measured plant cover to understand how shifts in vegetation influenced these wildlife species.
The results showed that summer cattle presence lowered rodent activity. Chipmunks, mice, ground squirrels and kangaroo rats were less active in grazed pastures — especially in summer — than in ungrazed controls.
In contrast, rodent activity in pastures grazed during the dormant season was like the ungrazed controls for most species, suggesting grazing outside of the breeding season likely had little effect on rodents. However, chipmunks were especially sensitive, with reduced activity under all grazing approaches.
Meso-predators — badgers and coyotes — responded to changes in plant cover and rodent (prey) activity more than cattle presence. The study did not detect a direct grazing effect on badgers or coyotes at the pasture scale.
Instead, meso-predator presence increased where plant communities supported prey. For example, where perennial forbs were more abundant, ground squirrel activity increased, which in turn was where badgers and coyotes were more likely to occupy.
The study highlights practical lessons for management:
- Timing and rotational grazing effects differ by species. While most rodent activity was reduced by summer grazing, rotational grazing — which alternates spring and summer grazing — mediated the effects of summer grazing on rodent species like ground squirrels and kangaroo rats.
- Repeated summer grazing should be avoided if rodents are wildlife species of concern.
- Alternatively, rotational grazing can be used as a management tool to reduce chipmunk and mouse activity if desired.
- Perennial forbs play a vital role in supporting rodent prey species’ activity and indirectly, their predators.
By showing how livestock grazing season of use and changes in plant cover influence small-mammal activity and predator presence, the study can help managers make informed decisions that support rural livelihoods while conserving wildlife.
This research has highlighted the need for further studies that can help land managers and agencies better understand the impacts of differing grazing strategies on ecosystem dynamics, including predator-prey relationships.
The study was published in the journal Rangeland & Ecology Management.
The research team included:
- Vanessa Schroeder, senior faculty research assistant, Eastern Oregon Agricultural Research Center (lead author)
- Dustin Johnson, professor of practice and Extension livestock and rangeland field faculty
- W. Douglas Robinson, Mace Professor of Watchable Wildlife, Department of Fisheries, Wildlife, and Conservation Sciences
- David Bohnert, director, Eastern Oregon Agricultural Research Center; ruminant nutritionist and Extension beef cattle specialist
- Jonathan Dinkins, associate professor, Department of Animal and Rangeland Sciences
Funding and support came from the Oregon Agricultural Experiment Station, the research arm of the College of Agricultural Sciences; OSU Extension Service, Eastern Oregon Agricultural Research Center, U.S. Department of Agriculture National Institute of Food and Agriculture, U.S. Fish and Wildlife Service, U.S. Bureau of Land Management and the Oregon Beef Council.