This summer, I was hiking in the Norwegian mountains and experienced a phenomenon known as smågnagerår or ‘little gnawing animal year’. It occurs when a particularly mild winter and plentiful summer create the perfect conditions for a boom in the population of Norwegian lemmings. The roly-poly yellow, black, and white striped little critters were everywhere – scurrying over rocks, hiding behind bushes, swimming across lakes, and running along the hiking trails. If you sat quietly, it was possible to watch them emerge from their hiding spots and nibble grasses or sun themselves on the rocks.
But with one wrong step, my peaceful ramble down the trail was interrupted by a piercingly shrill whistle followed by increasingly angry chatter. I froze, thinking I was disturbing some poor lemming mother and scanned the ground around me. I saw nothing, and the raucous got only louder and more vicious. That is until I lifted my left boot. An irate lemming popped out from among the branches beneath it lunged repeatedly at my toes while baring its comically small teeth before finally making a run for it beneath a rock.
I immediately laughed at the apparent suicidal tendencies of the little creature, attacking an animal twenty times its size after it had quite literally stepped on it and probably very nearly missed killing it. Although there are countless jokes about herds of suicidal lemmings jumping over cliffs, I’ve known for years that these are untrue, borne of exaggerated reports of the casualties sustained during lemming migrations. But why then would a lemming display what certainly appeared to be irrational suicidal behaviour? It turns out a suicidally brave temperament goes hand in hand with this little rodent’s flashy style. While other small rodents rely on their drab colours and stealthiness to blend in with their surroundings and quietly scurry away from potential predators, lemmings take a completely different approach. Rather than avoiding predators, lemmings rely on aposematism – a combination of visual and audio signals that warn predators that a potential prey item may be toxic or otherwise dangerous. The lemmings coat includes bold patches of reddy-brown, golden yellow, black and white, which makes them easy to spot among the vegetation. However, their bold coloration involves colours that many birds avoid in prey items. Similarly the loud defensive calls and aggressive, threatening behaviour is intended as further dissuasion, warning to predators that the lemming won’t go quietly and without a potentially damaging fight. And it works! Given the choice between a cowering vole paralyzed by fear, and the raging ball of fluff that is the lemming, predatory birds like the long-tailed skua preferentially select the voles. It is not all empty threats either, as lemmings have been known to kill stoats more than twice their size. In the end, the suicidal tendencies of lemmings probably save their lives more often than not!