Influence of habitat on fine-scale space use by brown lemmings (Lemmus trimucronatus) in the High Arctic

Abstract Space use by small mammals should mirror their immediate needs for food and predator shelters but can also be influenced by seasonal changes in biotic and abiotic factors. Lemmings are keystone species of the tundra food web, but information on their spatial distribution in relation to habitat heterogeneity is still scant, especially at a fine scale. In this study, we used spatially explicit capture–recapture methods to determine how topography, hydrology, vegetation, and soil characteristics influence the fine-scale spatial variations in summer density of brown lemmings (Lemmus trimucronatus). Lemmings were monitored throughout the summer in wet and mesic tundra habitats and in a predator exclusion grid, which was also located in mesic tundra. We found that in wet tundra, lemming densities were higher at sites with a rugged topography dominated by hummocks, but only during snow melt. In both mesic tundra sites, lemming densities were higher in sites with poor drainage and low aspect throughout the summer. We found no clear association between lemming densities and any tested vegetation or soil variables. Overall, hydrology and topography appear to play a dominant role in small-scale space use of brown lemmings with a secondary role for predator avoidance and food plant abundance. What leads lemmings to build their summer burrow here and not a few meters away? Here, we provide evidence that vegetation was not an important factor of fine-scale space use by brown lemmings (Lemmus trimucronatus), but topography and hydrology were. Lemmings avoided slopes, even mild ones, all summer long, used rugged hummocky habitat in the wet meadow habitat, and remained in poorly drained areas in the mesic tundra habitat. Overall, hydrology was critical for how lemmings used their immediate environment on Bylot Island, Nunavut, whereas avoiding predators and foraging appeared of secondary importance.