Abstract
The greater sage-grouse (Centrocercus urophasianus) has been declining across its range for decades, with low recruitment being a major contributing factor. Sage-grouse broods depend on a diet rich in forbs and insects, and on having vegetative cover available for predation avoidance. Forb species tend to occur in greater abundances and diversities in mesic areas compared to adjacent upland areas, which in turn, tends to promote greater insect abundances and diversities, too. The edge created where mesic and upland areas meet is also important as cover from predators in close proximity to preferred foraging areas. However, mesic areas are relatively rare across the sagebrush biome, and their persistence is threatened due to climate change and unsustainable land use practices. Thus, the availability of mesic resources is a critical factor affecting growth and survival of sage-grouse chicks. The North American beaver (Castor canadensis) has a demonstrated ability to completely reshape waterways that it inhabits through its engineering activity, promoting the availability of key mesic resources over time. As such, they have become a very common tool for mesic area restoration, especially in the arid and semi-arid western United States. When beaver occupation is not feasible, manmade beaver dam analogs, intended to mimic the form and function of natural beaver dams, have become a popular alternative. In this context, natural beaver dams and dam analogs are powerful management tools for promoting vital mesic resources within arid ecosystems, and therefore have great potential to benefit wildlife species, too. This interaction between beavers and other wildlife species is known as facilitation, whereby one species alters the environment in a way that benefits the fitness of a second, co-occurring species. However, little is known about the potential facilitative relationship that may exist between dam-modified mesic habitat and sage-grouse populations. Our goals in this study were to one, quantify brooding sage-grouse hen habitat selection with respect to dam-modified habitat at Rinker Rock Creek Ranch in Blaine County, Idaho, and two, to assess whether sage-grouse brood survival was affected by hen selection strength for dam-modified habitat. In this way, we would be able to link sage-grouse fitness with space-use decisions on the landscape, exploring the idea of a facilitative relationship. To address our first objective of quantifying brooding hen habitat selection with respect to dam-modified habitat on the landscape, we captured and tracked sage-grouse hens over two field seasons. In 2024 and 2025, we captured 53 sage-grouse hens and fitted them with GPS-VHF backpacks to track hourly movements and monitor nest and brood survival. We also censused 286 beaver dams in 2024 and 322 dams in 2025. We used an integrated step-selection analysis (iSSA) to quantify sage-grouse habitat selection during brood rearing with respect to habitat modified by beaver dams or analogs on the landscape. Our results did not provide strong support for any of our predictions under this objective. However, we detected strong individual variation in patterns of habitat selection, indicating that brooding hens are highly flexible in their resource use. In particular, we found that some brooding hens displayed a statistically significant selection for habitat closer to dams than farther away from them, when not using other types of mesic habitat. Besides this response to dams, patterns of habitat selection were consistent with results from past studies, such as selection for perennial forbs and grasses and closer distances to drainages.
To address our second objective of assessing sage-grouse brood survival as a function of hen selection for dam-modified habitat, we surveyed sage-grouse broods at five-day intervals to track brood survival over time. In our two seasons, we found 62 nests on the landscape, of which 18 successfully hatched chicks. 20 of these nests were found in 2024, of which 10 hatched, and the other 42 nests were found in 2025, of which eight hatched. Of these 18 total broods, four had one or more chicks detected at our final 50-day, post-hatch survey, all of which were in the 2024 season. We used a Cormack-Jolly-Seber model to quantify brood survival as a function of brooding hen selection for distance to dam-modified habitat, obtained through the iSSA. We found no evidence of improved brood survival for hens that selected habitat closer to beaver dams. However, our results and interpretation were likely hindered by a small sample size, considering most of the 18 broods that hatched never had chicks detected past the 5-day survey mark. The individual variation in selection for dam-modified habitat shows promise that with a larger sample size, we may have been able to better understand the consequences of brooding sage-grouse hen habitat selection on brood survival. Future projects should prioritize a long-term study with larger sample size goals to better address potential facilitation between beaver and beaver dam analogs and terrestrial wildlife.