Warmer and wetter winters are expected to hamper rodents access to food, resulting in dampened, irregular or lost rodent population cycles. A new study shows that across Fennoscandian tundra, areas with milder winter climate have lower amplitude population cycles.
Dead lemming on top of snowpack. Photo: Eeva Soininen
Small rodent population cycles differ across geographic regions. Surrogate variables such as latitude and elevation may explain some of this variation, but more mechanistic variables are needed to reach beyond pattern description. A study by COAT researchers and colleagues from Norway, Sweden and Finland collected time-series from 26 locations spanning 10 latitudinal degrees in the tundra biome of Fennoscandia and assessed how population dynamics varied with latitude and environmental variables.
Unlike previous studies, this study found no relationship between latitude and population cycle peak interval. The clearest latitudinal pattern was that going northward, grey-sided voles became more common and their population peaks higher.
Environmental variables provided insight into causes of these patterns, as 1) increased proportion of optimal habitat in the landscape led to higher density amplitudes in all species and 2) mid-winter climate variability lowered the amplitude in Norwegian lemmings and grey-sided voles.
These results indicate that biome-scale climate and landscape change can be expected to have profound impacts on rodent population cycles. Similar results have also been found in a study published in 2024, mapping lemming dynamics across the circumpolar Arctic. The 2024 study, which includes some of the same time-series as the newly published one, highlights especially the impacts of early winter snow conditions.
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