Sammendrag
Competition between individuals of the same or different species affects spatial distribution of organisms at any given time.
Consequently, a species geographical distribution is related to population dynamics through density-dependent processes.
Small Arctic rodents are important prey species in many Arctic ecosystems. They commonly show large cyclic fluctuations
in abundance offering a potential to investigate how landscape characteristics relates to density-dependent habitat selection.
Based on long-term summer trapping data of the Norwegian lemming (Lemmus lemmus) in the Scandinavian Mountain
tundra, we applied species distribution modeling to test if the effect of environmental variables on lemming distribution
changed in relation to the lemming cycle. Lemmings were less habitat specific during the peak phase, as their distribution
was only related to primary productivity. During the increase phase, however, lemming distribution was, in addition, associated
with landscape characteristics such as hilly terrain and slopes that are less likely to get flooded. Lemming habitat use
varied during the cycle, suggesting density-dependent changes in habitat selection that could be explained by intraspecific
competition. We believe that the distribution patterns observed during the increase phase show a stronger ecological signal
for habitat preference and that the less specific habitat use during the peak phase is a result of lemmings grazing themselves
out of the best habitat as the population grows. Future research on lemming winter distribution would make it possible to
investigate the year around strategies of habitat selection in lemmings and a better understanding of a fundamental actor in
many Arctic ecosystems.
Small rodents · Density-dependent · Competition · Habitat · Primary productivity
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