Managing multiple vital rates to maximize greater sage‐grouse population growth

Abstract

AbstractDespite decades of field research on greater sage‐grouse, range‐wide demographic data have yet to be synthesized into a sensitivity analysis to guide management actions. We reviewed range‐wide demographic rates for greater sage‐grouse from 1938 to 2011 and used data from 50 studies to parameterize a 2‐stage, female‐based population matrix model. We conducted life‐stage simulation analyses to determine the proportion of variation in population growth rate (λ) accounted for by each vital rate, and we calculated analytical sensitivity, elasticity, and variance‐stabilized sensitivity to identify the contribution of each vital rate to λ. As expected for an upland game bird, greater sage‐grouse showed marked annual and geographic variation in several vital rates. Three rates were demonstrably important for population growth: female survival, chick survival, and nest success. Female survival and chick survival, in that order, had the most influence on λ per unit change in vital rates. However, nest success explained more of the variation in λ than did the survival rates. In lieu of quantitative data on specific mortality factors driving local populations, we recommend that management efforts for greater sage‐grouse first focus on increasing female survival by restoring large, intact sagebrush‐steppe landscapes, reducing persistent sources of human‐caused mortality, and eliminating anthropogenic habitat features that subsidize species that prey on juvenile, yearling, and adult females. Our analysis also supports efforts to increase chick survival and nest success by eliminating anthropogenic habitat features that subsidize chick and nest predators, and by managing shrub, forb, and grass cover, height, and composition to meet local brood‐rearing and nesting habitat guidelines. We caution that habitat management to increase chick survival and nest success should not reduce the cover or height of sagebrush below that required for female survival in other seasons (e.g., fall, winter). The success or failure of management actions for sage‐grouse should be assessed by measuring changes in vital rates over long time periods to avoid confounding with natural, annual variation. © 2011 The Wildlife Society.