How often do lemming populations reach peak numbers in some Arctic regions?

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tundra biome — Polar ecosystem Southern limit of Arctic tundra and approximate line of demarcation between Low and High Arctic.

In Arctic regions, lemming populations undergo dramatic fluctuations, with peak numbers typically reached every two to five years or every three to five years, depending on the specific region.12

These cycles are characterized by periods of rapid population growth followed by sharp declines. During the peak of these cycles, lemming density can reach as high as 200 individuals per hectare, while during low points, the density may drop to fewer than one individual per hectare. These fluctuations are often linked to factors such as food availability, predation, and environmental conditions, including the quality of snow cover, which provides essential insulation and habitat for lemmings during the winter.3412