Spatial and temporal patterns of small-rodent population dynamics at a regional scale

Many species exhibit regional synchrony in population dynamics, and different influential biotic and abiotic factors can be indicated by the observed scale of spatial synchrony. Here, we present analyses of spatial patterns of bank vole Clethrionomys glareolus population fluctuations, based on a 5-yr (1990-1994) trapping series obtained from 31 trap stations regularly spaced along a 256-km transect in the boreal forest in southeastern Norway. The bank vole was known to exhibit typically cyclic population dynamics in this region prior to this study. Bank vole fall densities exhibited fluctuations with little year-to-year variation; all s-indices (a measure of temporal variability) were below 0.5. There was a large scale trend in the temporal variability of the populations, with highest variability at the south end and lowest in the middle of the transect. Analysis (Mantel correlogram) of the year-to-year rate of change of local populations showed that the opposite ends of the transect appeared to be most out of phase. At a smaller spatial scale (up to 30-40 km), local populations exhibited statistically significant synchrony in growth patterns. Spatiotemporal patterns in the dynamics of local populations were not related to habitat quality. We suggest that the scale domain of population synchrony is related to intrinsic population scaling properties such as dispersal capacity.