Sensitivity to weather drives Great Basin mesic resources and Greater Sage-Grouse productivity

Abstract

Anticipating and mitigating the effects climate change will have on wildlife populations requires an improved understanding of the ways in which those populations are currently adapted to climate and how they are affected by variation in weather conditions. We used over 70,000 greater sage-grouse (Centrocercus urophasianus) wings, derived from hunter harvest in three western states, to characterize spatiotemporal variation in sage-grouse productivity throughout the North American Great Basin during 1993 – 2020. We then tested the hypothesis that previously-identified associations between precipitation and sage-grouse productivity are mediated by the availability of mesic habitats, which provide the diet resources required by broods during typical late-summer seasonal drought. We used random forest regression to model sage-grouse productivity as a function of mesic habitat availability (defined as those areas with maximum Normalized Difference Vegetation Index (NDVI) ≥0.3) during the late brood-rearing period, the more general effect of annual precipitation, and landcover composition. We also evaluated potential acute direct effects of exposure to inclement weather on sage-grouse productivity. Finally, we examined which weather and topographic variables best predict mesic habitat availability. We found the predicted positive relationship between mesic habitat availability and sage-grouse productivity, but annual precipitation explained additional variation in productivity even after accounting for mesic habitat availability. Hence, precipitation and drought may drive sage-grouse productivity via more than one mechanism acting on multiple demographic rates. Productivity was also limited by exotic annual grass invasion and conifer encroachment. Mesic habitat availability was a function of topographic relief, mean elevation, annual mean snow water equivalent, and winter temperatures, indicating that snowpack recharges the late summer mesic resources that support sage-grouse productivity. Management actions focused on maintaining and restoring mesic resources and drought resilient habitats, limiting the spread of exotic annual grasses, and reversing conifer encroachment should support future sage-grouse recruitment and help mitigate the effects of climate change.

Keywords

• Annual grass
• Brood productivity
• Climate change
• Drought
• Mesic habitat
• NDVI