It’s often said that in a city you are never more than 2 metres from a rat. In the north of Scandinavia, in the middle of an Arctic winter, the same might be said of Norway’s most famous furry little mammal, the lemming. Every three to four years, when the conditions are right, you could be surrounded by hundreds of lemmings scurrying around in a network of branching tunnels beneath your feet.
When the population is at its lowest, lemmings will be so thin on the ground that there might be just one in 100,000 square meters. However, in good times the same area could be home to as many as 3000. This dramatic cycling of the population helps account for an enduring myth about lemmings: that they emerge from these burrows and run, en masse, to their death. “It is said they are marching to the sea and committing suicide,” says Nils Christian Stenseth of the University of Olso in Norway, and coauthor of The Biology of Lemmings, “which is of course a fable, and a result of the common habit of people to anthropomorphise animals.”
Accounts of lemming migrations go back hundreds of years. In 1823, for instance, one explorer wrote of seeing “inconceivable numbers” in his Scandinavian travels and an army of lemmings advancing with extraordinary purpose, “never suffering itself to be diverted from its course by any opposing obstacles” not even when confronted by rivers, or even the branches of narrow fjords. Given such sudden and apparently reckless behaviour, it is perhaps inevitable that local people in bygone centuries came to see the lemming as a crazed creature, and a swarm as the “forerunner of war and disaster. But we have Walt Disney to thank for really embedding this stereotype in the public consciousness, who undertook a series of feature-length nature documentaries known as True-life Adventures, one of which, White Wilderness, featuring a scene dramatising a lemming mass suicide.
There was little that was true in these True-life Adventures. For a start, White Wilderness-filmed in Canada rather than Scandinavia-depicts the wrong species of lemming. Although all lemmings experience population highs and lows, the accounts of mass movements were all based on observations of Norwegian lemmings, not the brown lemmings used in the film. In an infamous sequence, the lemmings reach the edge of a precipitous cliff, and the voiceover tells us that “this is the last chance to turn back, yet over they go, casting themselves bodily out into space.” It certainly looks like suicide. “Only they didn’t march to the sea,” says Stenseth. “They were tipped into it from the truck.” In the film we can see several of the brown lemmings pause at the edge. One or two look like they are trying to turn back. They don’t want to be there at all, let alone jump. If lemmings do not commit suicide, what are the causes and the consequences of these wild fluctuations in lemming numbers? Based on data collected between 1970 and 1997, Stenseth and his colleagues were able to demonstrate in 2008 that what lemmings really need to thrive is the right kind of snow. “If the snow is soft and dry then a space under the snow builds up within which the lemmings can survive very well during the winter and foster many offspring,” says Stenseth. If there are a couple of consecutive winters like this, vast numbers of lemmings can emerge in the spring. With too many hungry lemmings about, the vegetation quickly gets overgrazed and the animals are forced to seek new pastures. It is in these circumstances, as they move from higher to lower ground, that they can occasionally tumble down a slope. “By way of gravitation they tend to move downwards,” says Stenseth.
At its peak, the lemmings also become noticeably more aggressive. “A person walking across the meadow would cause the lemmings, several metres away, to give themselves away by unexpectedly shrieking and jumping about,” noted one group of researchers. “Even a farm tractor was greeted in this way, leaving a trail of infuriated lemmings behind it.” These displays of aggression may have fueled another age-old myth about lemmings: that they get so furious they explode. But this fanciful notion probably has a simple explanation. In the months after a reproductive boom, lemming predators will have a field day, slaying but not eating their victims. Once ravens have pecked their way through these killing fields, the eviscerated lemmings do look like they might have burst with anger. What’s more, as Stenseth points out, “no one has seen a lemming explode.”
1.Please list 3 of the reasons why people have an incorrect impression of lemmings and their behaviour? Answer this question in about 80 words. (8 points)
2.What are the truths behind the myths about lemmings? Answer this question in about 120 words. (16 points)
