Newswise — Research conducted by scientists at the University of Wyoming and other institutions suggests that conventional management practices aimed at enhancing sage grouse habitat may not only be ineffective but also have counterproductive effects.
Sagebrush reduction strategies, such as mowing and herbicide application, are commonly used to enhance the habitat of the greater sage grouse and other species dependent on sagebrush. The underlying concept is that removing large sagebrush shrubs improves the availability of food in nesting and brood-rearing areas for sage grouse, as it allows more nutritious vegetation to thrive with reduced competition. The anticipated result is an increase in invertebrate populations, which serve as an additional food source for sage grouse.
However, a recent publication in the journal Wildlife Monographs proposes that these approaches may be misdirected.
In a comprehensive nine-year experimental study, researchers analyzed the impact of mowing and the application of tebuthiuron, an herbicide, on Wyoming big sagebrush and its influence on sage grouse populations in central Wyoming. The data collected during the study indicated that these treatments did not yield any significant benefits for the birds.
Jeff Beck, a professor of ecosystem science and management at the University of Wyoming and the lead researcher of the study, expressed, "There is a perception among some managers that treating sagebrush for wildlife is the correct approach and should continue. However, it is our hope that this study will encourage individuals to consider alternative ideas if we are going to invest funds in habitat improvement."
The co-authors of the study include Kurt Smith, who was a former Ph.D. student at the University of Wyoming and is currently an ecologist at Western EcoSystems Technology. Jason LeVan, a former M.S. student at UW, is now a range and wildlife conservationist at Pheasants Forever. Anna Chalfoun, an associate professor at UW and assistant unit leader of the U.S. Geological Survey Wyoming Cooperative Fish and Wildlife Research Unit, also contributed to the research. Stanley Harter, a wildlife biologist at the Wyoming Game and Fish Department, Thomas Christiansen, a retired sage grouse program coordinator at the Wyoming Game and Fish Department, and Sue Oberlie, a retired wildlife biologist from the Bureau of Land Management (BLM), are also listed as co-authors.
Throughout the study, the researchers closely monitored the behaviors and survival rates of over 600 female greater sage grouse. They specifically examined how these factors were influenced by the application of mowing and tebuthiuron. In addition, the researchers carefully tracked the impact on invertebrate populations, as well as the growth of sagebrush and herbaceous vegetation. To establish a baseline for comparison, untreated plots near the treated areas and off-site control plots were also included in the study.
Data collection prior to the treatments took place between 2011 and 2013. The actual mowing and tebuthiuron applications were carried out during the winter and spring of 2014.
Following a six-year period of post-treatment monitoring spanning from 2014 to 2019, Beck and his colleagues concluded that the responses of sage grouse to the treatments were, at best, neutral.
The researchers reported that neither the mowing nor tebuthiuron treatments had any significant impact on nest success, brood success, or female survival.
Moreover, the treatments aimed at reducing the coverage of Wyoming big sagebrush resulted in a slight avoidance response from sage grouse.
Additionally, the reduction of Wyoming big sagebrush did not lead to positive responses in invertebrate populations and herbaceous vegetation. This suggests that the treatments did not enhance the quantity and quality of food sources for sage grouse.
The researchers suggest that instead of benefiting sage grouse and other species that rely on sagebrush shrubs for nesting and refuge from predators, the reduction of Wyoming big sagebrush cover may have a negative impact on these species.
The researchers propose that the reduction of Wyoming big sagebrush cover could have a detrimental effect on sage grouse and other species that rely on sagebrush shrubs for nesting and finding protection from predators.
According to the researchers' findings, "Management practices that prioritize the preservation of large, undisturbed expanses of sagebrush will be most effective in ensuring the long-term survival of sage grouse populations and other species dependent on the sagebrush steppe."
Their findings align with numerous other studies indicating that managing Wyoming big sagebrush has adverse effects on wildlife. However, the researchers caution against generalizing these results to other sagebrush species and subspecies, such as mountain big sagebrush.
Beck suggests that instead of removing Wyoming big sagebrush, conservation strategies should prioritize the removal of encroaching pinyon and juniper, as well as invasive species like cheatgrass. These vegetation types have a disruptive impact on the sagebrush ecosystem and affect fire cycles, which can potentially harm sage grouse habitat.
He also points out that enhancing wet areas within sagebrush habitats is a promising strategy to improve the quality of sage grouse brood-rearing habitat.
This research was supported by the Wyoming Game and Fish Department’s Wyoming Sage-grouse Conservation Fund; the Bates Hole, Big Horn Basin, South-Central, Southwest and Wind River/Sweetwater River local sage grouse working groups; the Wyoming Wildlife and Natural Resource Trust; the BLM’s Lander field office; the Margaret and Sam Kelly Ornithological Research Fund; and the Wyoming Reclamation and Restoration Center’s graduate assistantship program.
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