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What is a lemming year in Norway?

Peak years, their causes and the animals that depend on them.

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Short answer

A lemming year is a peak year for Norway's lemmings, which used to come every three to five years but now perhaps only every five to ten. In good lemming years arctic foxes can raise litters of more than ten pups, and snowy owls breed in Norway only when small rodents are very plentiful.

Rodents in Norway's ecosystem a dog with a leash sitting next to a small moose silhouette and a vet cross

Why

  1. Store norske leksikon notes that where lemming numbers used to peak every three to five years, this now perhaps happens only every five to ten years.
  2. Small rodent numbers can rise sharply with a good food supply, few predators and favourable weather, and a good snow cover in winter protects them.
  3. Arctic foxes depend on lemmings to raise pups: in good lemming years a litter often has more than ten pups, while in poor years few or none are born.

Details

Snowy owls need plenty of small rodents, especially lemmings, to breed, and for the last 30–40 years they have only nested from Børgefjell north to Troms and Finnmark. A poor snow cover with repeated thawing and freezing is bad for small rodents, and this is expected to become more common with climate change.

Tip

If you meet lemmings on a mountain hike, watch them from where you are: Visit Norway advises hikers not to approach wild animals.

What may differ

Other small rodents also have big swings in numbers, but for most species these swings are not very regular.

People also ask

  • Why are there so many lemmings in some years in Norway?

Sources

Information checked on 20 October 2026.

Rodents in Norway's ecosystem

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