The mysterious population cycle of lemmings may finally have an explanation

Arctic chicken nuggets have strange boom-and-bust cycles, leading to the story of lemmings committing suicide en masse when they become too numerous. That is false. These scientists may have the real answer.

If you know less about lemmings than Dominique Fauteux, and you almost certainly do, then what you know about lemmings is probably false. And it probably goes something like this: Lemmings follow each other in a mindless herd, and when they feel like it, they commit suicide en masse by jumping off any accessible cliff.

The legends, misunderstandings, and outright fraud that added to that reputation are based on the mysterious population cycles that make tiny rodents fascinating to Fauteux, a research scientist in zoology at the Natural Heritage Campus of the Canadian Museum of Science. Nature in Gatineau, Que. Lemmings undergo population cycles lasting three to four years, during which their numbers can fluctuate a hundred times.

So Fauteux and his team, who work each summer at research sites on Bylot Island and Cambridge Bay in Nunavut, and near Salluit in northern Quebec, will see a “bud” with a bumper crop of lemmings one year. before their number drops almost to zero. the following year, and maybe stay that way for another season before suddenly exploding again. “You have a new outbreak, with lemmings all over the place,” says Fauteux. “You have to be careful not to step on them.”

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Those bizarre boom-bust cycles led to the story of lemmings committing mass suicide when they become too numerous. But it was the 1958 Walt Disney Productions movie White desert that cemented that myth, with images of lemmings charging up a cliff. It was advertised as a documentary, but the scene was false, with people behind the camera leading the animals to their staged deaths. “You can see the anguish in the lemmings,” says Fauteux of the scene. “You can clearly see that when they fell off the cliff, they weren’t prepared for it at all.”

The real reasons their populations fluctuate have been the subject of scientific intrigue for decades. And after massive numbers of lemmings were observed earlier than expected in their population cycle last year, Fauteux and his team hope they can solve this enduring puzzle in 2022.

Lemmings are unusual rodents as they breed during the winter, under the snow. A female can reproduce four to five times during the nine months of the Arctic winter, with up to seven young per litter. Fauteux’s team believes that predation is what drives the dramatic population trends, but how that could happen involves a complicated six-degree arctic-spaced web.

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Lemmings are preyed upon by snowy owls, long-tailed jaegers, hawks, hawks, cranes, arctic foxes, and stoats. “They are the ones that are eaten because they are easier to find, easier to catch and they are everywhere,” says Fauteux. “They are like little chicken nuggets running through the tundra.” All birds on the lemming predator list migrate, leaving the last two as the only winter predators.

Fauteux’s team hypothesizes that ermine is factor X, because it is not present in the ecosystem every year, yet researchers see that lemming populations decline when they are there. To test this, after the snow melts in June, the researchers will collect and examine lemming nests built from dry grasses. Arctic foxes cannot fit in nests, so any evidence of predation (a piece of fur, say, or a severed leg) points to stoats as executioners. The efficiency of stoats at killing lemmings could explain why there are years when their population does not recover. Fauteux’s team has wooden boxes that they use to catch lemmings for study, and they returned one summer to find that the ermines had turned one into a winter pantry. “It’s kind of disgusting,” he says. “We found 28 carcasses of lemmings hidden in one.”

They have observed that when there are many snowy owls, which feed on stoats, the decline in lemmings does not occur. That, in turn, could explain the ermine fluctuation.

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One effect of climate change that could affect lemmings is more frequent rain-on-snow events, which create a layer of hard ice that makes it difficult for them to dig their nests. Fauteux’s team tested this in the lab by simulating rain on snow samples they collected and then observing the burrows of the lemmings they caught for study. Lemmings went from using their claws to using their teeth to break ice. Fauteux finds this adaptation impressive, but says it could eventually require too much energy from them, leading to death or reduced reproduction. “Ultimately, we don’t expect the lemmings to go away,” he says, “but we certainly expect the peaks, the amplitude of the cycles, to decrease.”

These little arctic chicken nuggets are critical to the rest of the food chain above them. In Norway, arctic foxes relied on lemming booms to reproduce well, and their population is now in danger. In Greenland, there was no lemming outbreak for eight years, and snowy owls declined 98% in the same period. “It’s no wonder that famous environmentalists have been studying them since 1924,” says Fauteux. “In an ecological way, they are really mysterious.”

As a student, Fauteux spent three months each summer in the Arctic, in his opinion “one of the most beautiful places on Earth.” Even when focusing on specific scientific questions, he says, “You see everything connected, everything happens at the same time.” Now that he has greater responsibilities, Fauteux’s time on the field is shorter, and those are the weeks of 2022 he will be waiting for.

This article appears in print in the January 2022 issue of Maclean’s magazine with the headline, “When life serves them lemmings.” Subscribe to the monthly print magazine here.

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