Characteristics of climate and landscape disturbance influence the dynamics of greater sage-grouse populations

Life histories determine how organisms interact with their environment and predict how populations respond to environmental change. Understanding relationships between life histories and environmental variability is therefore crucial for effective conservation under changing environmental conditions. Greater sage-grouse (Centrocercus urophasianus) is a species of major conservation concern in western North America following widespread disturbance of the sagebrush ecosystems to which they are endemic. Using robust design and Pradel capture-mark-recapture models, we evaluated the influence of climatic processes and disturbance associated with post-wildfire exotic grass invasion on annual survival, per-capita recruitment, and population growth of breeding male sage-grouse in eastern Nevada, USA. Climatic processes, indexed by annual rainfall and maximum summertime temperatures, had a strong relationship with recruitment and adult survival, respectively. The range of variation in recruitment during the study was greater than the range of variation in survival, consistent with a life-history strategy that features lengthened lifespan to capitalize on periodically favorable reproductive conditions. Annual variation in precipitation variables (e. g., rainfall or snow depth) explained as much as 75% of the annual variance in population size during the study. Our results are consistent with bottom-up regulation of sage-grouse populations, where abundance is determined in large part by climate-driven variation in resource availability. Exotic grasslands had a negative influence on recruitment that was interactive with annual rainfall; recruitment was consistently low in areas with a substantial exotic grassland footprint even following years of favorable rainfall. We found males breeding at leks with substantial exotic grassland impacts had lower annual survival compared to males at leks surrounded by native sagebrush habitats. However, models containing an interaction between exotic grasslands and maximum summer temperature were not clearly superior to models that considered only additive effects of the two variables. This research has significant implications for sage-grouse persistence in a changing climate, where more frequent drought and increased spread of exotic grasslands will have negative impacts on sage-grouse populations.