In early June, the University of Idaho (U of I) released the final results of its 10-year study evaluating the effects of spring cattle grazing on greater sage-grouse. The study concluded that cattle grazing not only does no harm to sage grouse, but actually benefits the species by building habitat, increasing forage and reducing invasive grasses that lead to wildfires.
“Decisions regarding sage grouse and cattle were being made by land managers, but there wasn’t a lot of science to rely on,” said Courtney Conway, lead study author and U of I professor of wildlife sciences and the leader of the U.S. Geological Survey Idaho Cooperative Fish and Wildlife Research Unit. “We just didn’t know what effect spring grazing had on nesting sage-grouse, brood production or other vital rates, until now.”
Conway’s idea for the study was spurred by the growing opposition to cattle grazing on federal land in the early 2000s. Conway collaborated with U of I professor of rangeland ecology Karen Launchbaugh, biologists with the Bureau of Land Management (BLM), the Idaho Department of Fish and Game, the Idaho Governor’s Office of Species Conservation and local Idaho ranchers to gather data over the 10-year-long study.
“Based on results of this research, livestock grazing, when properly managed, does not appear to negatively impact sage-grouse nest survival or brood success,” the study read.
Although the study concluded in August 2023, the final study was published June 6 on the U.S. Fish and Wildlife Service’s website. To view the study in its entirety, visit tinyurl.com/35b4mkh9.
Study details
Preliminary study results were shared last year confirming that grazing benefits sage grouse populations and does not negatively affect nesting success. The final study reiterates the preliminary data that supports the benefits of grazing.
“I think this is a significant outcome for the ranching community, which has wondered all along what they would do if scientists learned that their spring grazing was bad for sage grouse,” said Launchbaugh, co-lead investigator. “We now have rigorous scientific results to support the idea that cattle and sage-grouse can co-exist under the scenarios we examined. These findings suggest that responsible public land grazing can continue without harming sage-grouse.”
The group of researchers collaborated with local ranchers holding BLM grazing permits from 2013 to 2023. Researchers collected and analyzed data on an annual basis from five research sites in Idaho, addressing the effects of currently permitted low-to-moderate grazing levels on sage grouse. The study noted that more intensive grazing could show different outcomes.
More than 1,300 sage grouse hens were captured and collared across the five research sites. Researchers documented 1,285 nests and tracked 399 broods to assess the effects of spring cattle grazing on sage grouse populations. Because insects are important food sources for sage grouse hens and their chicks, researchers also examined insect biomass and diversity.
Three or four grazing treatments were applied at each study site after two years of pre-treatment field investigations. The controlled cattle grazing treatments included spring grazing in even years, spring grazing in odd years, spring and fall grazing in alternating years, and no grazing (control). Once grazing treatments were implemented, the researchers measured sage grouse demographic traits for four to eight years post-treatment.
Stocking rates were assessed each year. Grazed pastures showed lower grass cover and height compared to the no grazing pastures, which varied based on annual precipitation levels. Rested pastures maintained higher grass cover and height, but the differences in habitat structure did not consistently show a difference in sage grouse demographic traits, the researchers said.
“At the pasture scale, this study has found that sage-grouse nesting success is no greater in pastures that were rested for 4-8 years than those currently or recently grazed,” the study read. “This study gives no indication that removing cattle from pastures affected nesting success.”
While nest density varied among the grazing treatments, there was no compelling evidence that nesting hen density increased following the halt of grazing in the no-grazing treatments. In addition, climactic conditions were shown to have a greater effect on brood survival than grazing metrics.
Study support
The National Cattlemen’s Beef Association (NCBA), Public Lands Council (PLC), Idaho Cattle Association (ICA) and Idaho Public Lands Council (IPLC) supported the project over its 10-year course. The groups have highlighted the benefits of grazing for decades and applauded the research as a landmark study to be a point of reference for anyone questioning grazing in the future.
“Knowing the importance of the study, IPLC approached the national PLC with a grant application to support the project,” said Darcy Helmick, research partner and IPLC board member. “With PLC and ICA support, as well as many other partners, the 10-year study was completed.”
Helmick added: “We are not surprised by the results, and believe the results in this important research will be a critical component in future grouse management moving forward.”
NCBA President Buck Wehrbein said the study is another example of ranchers being the original conservationists. “For years, those with ulterior motives have perpetuated the myth that cattle production negatively impacted sage grouse populations,” Wehrbein said. “Nothing could be further from the truth and anyone that has worked on a cattle operation with or without grouse nesting knows that grazing improves rangeland health and with it the wildlife that live on working lands.”
The study was funded by grants from the U.S. Forest Service, U.S. Fish and Wildlife Service, U.S. Geological Survey and BLM. — Anna Miller Fortozo, WLJ managing editor
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