Survival of juvenile greater sage‐grouse in Wyoming

Abstract

An understanding of vital rate contributions to population growth is necessary for species of conservation concern, such as greater sage‐grouse Centrocercus urophasianus. Sage‐grouse demographic rates are generally well described; however, a notable exception is juvenile survival during the post‐fledging period. We evaluated juvenile survival at two study areas in central and south–central Wyoming. We captured and monitored 124 juvenile sage‐grouse (77 females and 47 males) in 2017–2019 in the central Wyoming study area and 68 (29 females and 39 males) in 2020–2021 in the south–central Wyoming study area. Monthly survival generally increased from September to March in each year and study area. In both study areas, we found no evidence that monthly mortality risk differed between male and female juvenile sage‐grouse. In central Wyoming, seven‐month survival estimates from September to March were 0.28 (85% CI: 0.18–0.44) from 2017–2018, 0.28 (85% CI: 0.20–0.39) from 2018–2019, and 0.43 (85% CI: 0.34–0.55) from 2019–2020. In south‐central Wyoming, survival estimates were 0.34 (85% CI: 0.25–0.47) from 2020–2021 and 0.78 (85% CI: 0.68–0.90) from 2021–2022. Overall, we found evidence that body condition at time of capture and weather (temperature and precipitation) during the pre‐fledging period influenced juvenile mortality risk, but the most supported intrinsic and extrinsic factors varied between study areas. Our results provide additional estimates of juvenile survival that will be useful for understanding sage‐grouse demography. However, the spatial and temporal variation in juvenile survival that we documented should be accounted for when evaluating how management actions may influence sage‐grouse populations.