CORVALLIS, Ore. — New research finds mixed results on how hunting regulations affect population growth in two sage-grouse species in western North America.
In their analysis of 22 relatively distinct population segments, the researchers compared counts to evaluate the effects of hunting restrictions. Some populations decreased, others increased and some remained stable as other environmental pressures were considered.
The distribution and abundance of greater sage-grouse and Gunnison sage-grouse have steadily declined across the region over the past century. To help guide conservation, researchers led by the Oregon State University Extension Service examined whether hunting influences population trends.
Jonathan Dinkins, an Extension assistant professor in the OSU College of Agricultural Sciences, collaborated with Jeff Beck, a professor at the University of Wyoming, to review the history of sage-grouse populations and hunting regulations across 11 western U.S. states and two Canadian provinces from the late 1800s to the present.
The results, which varied by location and context, appear in two articles in the open-access journal PLOS ONE.
“Hunting is a potential factor contributing to population declines of sage-grouse but has been difficult to fully assess,” Dinkins said. “As a result, wildlife agencies throughout western North America set increasingly more conservative harvest regulations over the past 25 years to reduce or eliminate the numbers of harvested greater sage-grouse and Gunnison sage-grouse.”
In their analysis of 22 relatively distinct population segments, the researchers compared counts to evaluate the effects of hunting restrictions. Some populations decreased, others increased and some remained stable as other environmental pressures were considered, Dinkins said.
“Our results suggest that discontinuing hunting in the largest population in central Idaho — using a study designed specifically to evaluate hunting effects on sage-grouse — resulted in greater population growth rates,” he said. “However, this was not consistently the case for smaller populations. To no surprise, not all sage-grouse populations were influenced by the same environmental change or human disturbance factors.”
Habitat pressures also drive long-term declines
To persist, sage-grouse need expansive, connected habitat dominated by sagebrush with an understory of native grasses and wildflowers. Multiple factors contribute to long-term declines, including wildfires, disease, drought, conifer encroachment, invasive annual grasses and human development such as oil and gas development, wind turbines and housing construction. Hunting is also a consideration.
The region-wide decline has ebbed and flowed since the 1800s, when millions of the chicken-sized birds were harvested. As state management agencies formed in the 20th century, regulations—including full closures—were adopted to avoid overharvesting. Even so, populations fluctuated, and by the 1980s and 1990s the decline was serious enough that the species was considered for protection under the Endangered Species Act.
“Understanding the effects of human hunting on wildlife populations is necessary under any management scenario, but especially critical when managing declining populations or species of conservation interest,” said Dinkins, who studied potential hunting effects on sage-grouse as a postdoctoral researcher at the University of Wyoming before joining Oregon State in 2016.
Informing management decisions
Overall, Dinkins said, federal and state agencies are doing a good job regulating hunting and providing opportunities for public recreation.
Findings from this work will help management agencies interpret population trends and focus conservation efforts.
Previously titled Sage grouse studies find mixed results from hunting restrictions in West
