The spatial scale of variability in small‐mammal populations

We studied small‐mammal populations across a range of spatial scales to determine which scales were relevant to demographic variability. We predicted that a scale of variability in population structure would occur at the scale of dispersal, which has previously been described as < 200 m for some small‐mammal species. Systematic live‐trapping surveys were conducted on nested grids at three scales: 1) extent = 4900 ha. grain =1000 m; 2) extent = 306 ha, grain = 250 m: and 3) extent = 31 ha. grain = 125 m. Prior to the present study, small‐mammal populations had not been systematically live‐trapped across a similar range of scales. From 1996 to 1998, surveys were conducted on a landscape intensively managed for timber, and on a reference landscape. Spatial analysis of abundance data demonstrated that small‐mammal populations (four species) exhibited positive spatial autocorrelation at distances of between 133 and 533 m depending on the species and the landscape. No higher‐order population structure was detected. Thus, within the range of scales we sampled, variability in small‐mammal abundance occurred over short distances (i.e. 133–533 m).