Historical Trends in Collared Lemming (Dicrostonym Richardsoni) Abundance and Nest Success of Eastern Prairie Population (EPP) Canada Geese (Branta Canadensis Interior) In Northern Manitoba: Evaluating the "Bird-Lemming" Hypothesis

Abstract

Regular, multi-annual cycles observed in the population abundance of small mammals in arctic and sub-arctic ecosystems across many regions has stimulated substantial research, particularly among population ecologists. Hypotheses addressing the cause of regular cycles include mechanisms such as predator-prey interactions, limitation of food resources, and migration or dispersal, as well as abiotic factors such as cyclic climatic variation and environmental stochasticity. However, long-term time-series of population data for small mammals in North America are generally lacking. Small rodent abundance is typically quantified by trapping grids and capture-mark-recapture techniques. These methods are time-consuming and provide data only for the time period during which trapping occurred. Alternative approaches may provide useful information regarding population trends, especially in remote areas where logistics make intensive trapping and marking of individual small mammals impractical. In 2004 and 2005, we used indirect methods to estimate trends in population size of collared lemmings (Dicrostonyx richardsoni), and evaluated the extent of synchrony between lemming populations at 2 coastal tundra study areas separated by ~ 60 km near Cape Churchill, Manitoba, Canada. We collected scars on willow plants (Salix spp.) resulting from lemming feeding. Scarages ranged from 0 to 13 years at both study areas. Scar-age frequency appeared cyclic and we used Poisson regression to model the observed scar-age frequency. Lemming populations cycled with 2.83 year periodicity and the phase of the cycle was synchronous between the 2 study areas. Modeling scar-age frequency data resulted in estimates of relative lemming abundance at broad spatial and temporal scales, and allowed us to evaluate synchrony between study areas.