Small Mammals Cycles in Northern Europe: Patterns and Evidence for a Maternal Effect Hypothesis

1. Voles undergo pronounced oscillations over periods of 3-5 years in northern Europe. A latitudinal gradient of cycle periods and amplitudes has been reported for Fennoscandia, with periods and amplitudes increasing towards northern latitudes. 2. This study formulates a discrete time model based on maternal effects to explain the density fluctuation patterns of microtine rodents. The phenotypic transmission of quality from mothers to offspring generates delayed density dependence, which produces cyclic behaviour in the model. 3. The dynamic patterns predicted by the maternal effect model agree with data. We conclude that the maternal effect hypothesis is a plausible, parsimonious explanation for vole-density cycles in northern Europe.