Spatial Asynchrony and Demographic Traveling Waves during Red Grouse Population Cycles

Abstract

Red Grouse (Lagopus lagopus scoticus) showed two population density cycles during an 18-yr study on 14 km2 of heather moorland that formed part of a larger moorland tract in northeast Scotland. Fluctuations on 22 different parts of the study area were somewhat asynchronous. Synchrony between parts decreased with distance. The dependence of densities in adjacent parts upon one another was analyzed in two stages. First, population trajectories were modeled with no time component. Second, the fit of these models was significantly improved by adding a time component. This provided evidence for a demographic wave traveling at 2–3 km/yr. It traveled from the center of the moorland tract toward its margin, which adjoined farms and woodland unoccupied by grouse.