Erlend Haarberg / Norway lemming (Lemmus lemmus) jumping aggressively, during the lemming population explosion, Vauldalen, Norway, May, 2011.

Erlend Haarberg / Norway lemming (Lemmus lemmus) calling on spring snow, Vauldalen, Norway, May

Erlend Haarberg / Two Norway lemmings (Lemmus lemmus) interacting on spring snow, Vauldalen, Norway, April

Erlend Haarberg / Norway lemming (Lemmus lemmus) swimming, Sweden, May

Bengt Lundberg / Norway lemming on snow {Lemmus lemmus} Sweden

Espen Bergersen / Norwegian lemming (Lemmus lemmus) peering out from under rock, Troms. Norway.

Espen Bergersen / Norwegian lemming (Lemmus lemmus) profile, Troms. Norway.

Espen Bergersen / Norwegian lemming (Lemmus lemmus) on path, Troms. Norway.

Espen Bergersen / Norwegian lemming (Lemmus lemmus) portrait, Troms. Norway.

Erlend Haarberg / Norway lemming (Lemmus lemmus) in nest box, Vauldalen, Norway, June.

Erlend Haarberg / Norway lemming (Lemmus lemmus) on snow, during the lemming population explosion, Vauldalen, Norway, May, 2011.

Erlend Haarberg / Arctic fox (Alopex lagopus) adult female with Norway lemming (Lemmus lemmus) in mouth, Dovrefjell-Sunndalsfjella National Park, Norway, July.