Greater Sage-Grouse Survival, Breeding Ecology, Resource Selection, and West Nile Virus Prevalence on the Eastern Fringe of their Range

Abstract

The greater sage-grouse (Centrocercus urophasianus) is a sagebrush (Artemisia spp.) obligate species that has experienced population declines over the past several decades. Sage-grouse are a species of conservation concern throughout the Intermountain West and are considered a species of greatest conservation need in South Dakota. Numerous studies have documented drivers of demographic performance at the core of their distribution; however, relatively few studies have examined sage-grouse inhabiting the eastern extent of their range, in South Dakota. We sought to examine sage-grouse space use in multiple seasons, estimate survival, and determine factors affecting nest success in South Dakota during 2016 and 2017. Additionally, we quantified resource selection during spring/summer, winter, at nest-sites, and at brood-sites. Lastly, sagegrouse are highly susceptible to West Nile virus (WNV); thus, we evaluated the impact of WNV to this population of sage-grouse while simultaneously estimating infection rates in the primary arthropod vector, Culex tarsalis. We found that at a landscape scale, sagegrouse consistently exhibit positive selection responses to sagebrush and leks, and negative responses to forest, roads, and rugged terrain. At a local scale, when selecting nest-sites and brood-sites, sage-grouse consistently select for shrub cover and taller grass, while avoiding areas with greater percent grass cover. Estimated nest success was 29% (95% CI=20−42%). Distance to forest, distance to lek, road density, and percent undisturbed (unplowed) land had the greatest influenced on nest survival. Using remotely triggered cameras, we identified the American badger (Taxidea taxus) as the primary nest predator of sage-grouse. Adult female sage-grouse survival during the reproductive season (1 April−15 September) was estimated to be 68% (95% CI=56–78%). Survival varied temporally with lower survival during the nesting season compared to other periods during the reproductive season. We observed limited resistance to WNV (Culex tarsalis (minimum infection rate=1.6−3.3/1,000 mosquitoes tested). We did not observe a severe WNV outbreak during our study, but these data do serve as a baseline for enzootic levels of the virus in this landscape. Lastly, with our data we were able to develop a priority sage-grouse area in South Dakota, which encompasses known utilization as well as predicted use. Overall, this research has provided data from a population with limited prior information, as well as provided information that can enhance landscape management for the species