Greater Sage-Grouse survival varies with breeding season events in West Nile virus non-outbreak years

Abstract

Greater Sage-Grouse (Centrocercus urophasianus) is a species of conservation concern and is highly susceptible to mortality from West Nile virus (WNV). Culex tarsalis, a mosquito species, is the suspected primary vector for transmitting WNV to sage-grouse. We captured, radio-tagged, and monitored female sage-grouse to estimate breeding season (April 15 to September 15) survival, 2016–2017. Deceased sage-grouse were tested for active WNV; live-captured and hunter-harvested sage-grouse were tested for WNV antibody titers. Additionally, we trapped mosquitoes with CO2-baited traps 4 nights per week (542 trap nights) to estimate WNV minimum infection rate (MIR). Eight sage-grouse mortalities occurred during the WNV seasons of 2016 and 2017, 5 had recoverable tissue, and 1 of 5 tested positive for WNV infection. Survival varied temporally with sage-grouse biological seasons, not WNV seasonality. Survival was 0.68 (95% CI: 0.56–0.78; n = 74) during the reproductive season (April 1 to September 15). Mammalian predators were the leading suspected cause of mortality (40%), followed by unknown cause (25%), avian predation (15%), unknown predation (15%), and WNV (5%). These results indicate WNV was not a significant driver of adult sage-grouse survival during this study. Three sage-grouse (1.9%; 95% CI: 0.5–5.9%) contained WNV antibodies. We captured 12,472 mosquitoes of which 3,933 (32%) were C. tarsalis. The estimated WNV MIR of C. tarsalis during 2016 and 2017 was 3.3 and 1.6, respectively. Our results suggest sage-grouse in South Dakota have limited exposure to WNV, and WNV was not a significant source of sage-grouse mortality in South Dakota during 2016 and 2017. Based on our finding that a majority of sage-grouse in South Dakota are susceptible to WNV infection, WNV could potentially have an impact on the population during an epizootic event; however, when WNV is at or near-endemic levels, it appears to have little impact on sage-grouse survival.

Using Opportunistic Samples to Monitor West Nile Virus Infection Status in Greater Sage-Grouse (Centrocercus urophasianus) in Wyoming, USA (2020–22)

“…In Wyoming, there has been a paucity of published data on surveillance of WNV in the GRSG since the early 2000s, after initial detection in the state, despite continued concerns over the conservation status of this species (Naugle et al 2004;Clark et al 2006;Walker et al 2007). The lack of detectable antibodies to WNV in GRSG in our study is similar to that of previous work that yielded findings of low (Walker et al 2007;Dusek et al 2014;Parsons et al 2021) to no detectable antibodies (Naugle et al 2004(Naugle et al , 2005Sinai et al 2017; Table 2). Results from this and past studies (Clark et al 2006;Dusek et al 2014;Sinai et al 2017) reveal that GRSG WNV survivors are rarely detected on the landscape, suggesting that GRSG may be highly susceptible to WNV infections, with high mortality rates (Clark et al 2006;Nemeth et al 2021).…”

“…For GRSG, WNV infection was first documented in northeastern Wyoming in 2003 (Naugle et al 2004(Naugle et al , 2005Walker and Naugle 2011), followed by numerous cases reported across additional native range portions (Dusek et al 2014;Parsons et al 2021). Along with the apparently high susceptibility to WNV in GRSG, this species is presumed to be a competent reservoir host (Clark et al 2006).…”

“…For example, the presence of artificial water bodies (providing standing water with organic matter content) appears to increase availability of mosquito breeding habitat, increasing abundance in arid areas (Zou et al 2006;Doherty 2007;Reisen 2012). In addition, adult presence of C. tarsalis has been confirmed in areas occupied by GRSG and some of those C. tarsalis tested positive for WNV (Naugle et al 2004(Naugle et al , 2005Parsons et al 2021). In Wyoming, from 1999 to 2020, 762 cases of human disease (HD) and 185 cases of human neuroinvasive disease (HND) were reported (Centers for Disease Control and Prevention 2021).…”

Casting the Net Widely for Change in Animal Welfare: The Plight of Birds in Zoos, Ex Situ Conservation, and Conservation Fieldwork

“…As in most cases, the reasons for sharp population declines tend to be manifold and the result of multiple confounding changes. In the case of sage grouse, there were identified changes in the environment such as encroachment of plants [ 196 ], disease such as the West Nile virus [ 197 ], and a variety of industry activities, hunting, and other human undertakings [ 198 , 199 , 200 ] that made the project largely fail. All known successful translocations have involved at least some birds that have been captured from the wild.…”