Lemming populations are generally characterised by their cyclic nature, yet empirical data to support this are lacking for most species, largely because of the time and expense necessary to collect long-term population data. In this study we use the relative frequency of yearly willow scarring by lemmings as an index of lemming abundance, allowing us to plot population changes over a 34-year period. Scars were collected from 18 sites in Arctic North America separated by 2-1,647 km to investigate local synchrony among separate …