For centuries, people have puzzled over lemmings, the northern rodents whose populations surge and crash so quickly and so regularly that they inspired an enduring myth: that lemmings commit mass suicide when their numbers grow too large, eagerly pitching themselves off cliffs to their deaths in a foamy sea.
Scientists debunked that notion decades ago. But they have never been certain what causes the rapid boom-and-bust cycles that gave rise to it. Now, in a study of collared lemmings in Greenland, published on Friday in the journal Science, a team of European researchers reported that the real reason has nothing to do with self-annihilation and everything to do with hungry predators.
After 15 years of research, the scientists report, they discovered that the combined actions of four predator species -- snowy owls, seabirds called long-tailed skuas, arctic foxes and weasel-like creatures known as stoats -- create the four-year cycles during which lemming populations explode and then nearly disappear.
Scientists say such cycles have been one of the most enduring -- and hotly debated -- mysteries in ecology.
"There have been several dozen hypotheses and sometimes everybody was almost killing each other they were sticking so close to their hypothesis," said Olivier Gilg, an ecologist at the University of Helsinki in Finland who is an author of the paper.
Many suspected the cycles might be caused by an array of forces, Gilg said, "but we were able to explain this cycle with only predation, and that was very surprising; it was very exciting."
Peter Hudson, a population ecologist at Penn State University who was not involved with the work but who wrote a commentary for Science on the paper, called it a textbook case, noting that population cycles are also found in birds, insects and larger mammals, like lynx.
"These animals show this lovely clockwork change in numbers," he said of lemmings, "and yet we haven't been able to nail it down. This paper reveals the mechanism. That's why this study is particularly important."
Though their research deals with brown 18cm rodents, ecologists can be forgiven their excitement. Lemming population cycles have captured human imagination for hundreds of years. In Scandinavia, ancient sagas describe lemming outbreaks, and as early as the 1500s there were writings attempting to explain why lemmings would periodically overrun regions, some suggesting that the animals rained down from the sky.
Recently, scientists have tested more plausible explanations, including climate change and the idea that the quality of plants eaten by lemmings might vary cyclically or that high densities might stress lemmings, decreasing their ability to reproduce and causing populations to crash. Even sunspots had been proposed as a possible cause.
In the new study, researchers took advantage of Greenland's never-ending daylight in summer to do extended observations of predators. The open tundra environment also allowed the small, skittering rodents to be seen and counted easily.
The scientists found that the tundra provided an excess of food and of sandy soil to burrow in, a setting for explosive lemming population growth.
But when lemming numbers began to soar, foxes, skuas and owls began eating them in greater and greater quantity. A pair of snowy owls can bring back as many as 50 lemmings a day for their hungry nestlings.
Stoats specialize in hunting lemmings, and after a banner lemming year, stoat populations explode, decimating the lemmings the following year. Then the four-year cycle begins all over again.
When researchers created a model to predict lemming populations, based only on the behavior of their four predators, they found that the model precisely predicted nature's four-year fluctuations in numbers.
Despite the new finding, lemming scientists expect to continue to be plagued by suicide queries. In particular, they blame a 1958 Walt Disney nature film, White Wilderness, in which lemmings were shown hurling themselves off a cliff.
In 1983 a Canadian documentary, Cruel Camera, about abuse of animals in movies, asserted that the scene was faked, using lemmings bought from Eskimo children and herded into the water. That conclusion has come to be widely accepted, and on Thursday Rena Langley, a spokeswoman for the Walt Disney Co, did not dispute it.
"We have done extensive research into what happened more than 40 years ago," she said, "but have been unable to determine exactly what techniques were used in producing White Wilderness. The standards and techniques were certainly different then than they are now."
POLITICAL PRISONERS VS DEPORTEES: Venezuela’s prosecutor’s office slammed the call by El Salvador’s leader, accusing him of crimes against humanity Salvadoran President Nayib Bukele on Sunday proposed carrying out a prisoner swap with Venezuela, suggesting he would exchange Venezuelan deportees from the US his government has kept imprisoned for what he called “political prisoners” in Venezuela. In a post on X, directed at Venezuelan President Nicolas Maduro, Bukele listed off a number of family members of high-level opposition figures in Venezuela, journalists and activists detained during the South American government’s electoral crackdown last year. “The only reason they are imprisoned is for having opposed you and your electoral fraud,” he wrote to Maduro. “However, I want to propose a humanitarian agreement that
ECONOMIC WORRIES: The ruling PAP faces voters amid concerns that the city-state faces the possibility of a recession and job losses amid Washington’s tariffs Singapore yesterday finalized contestants for its general election on Saturday next week, with the ruling People’s Action Party (PAP) fielding 32 new candidates in the biggest refresh of the party that has ruled the city-state since independence in 1965. The move follows a pledge by Singaporean Prime Minister Lawrence Wong (黃循財), who took office last year and assumed the PAP leadership, to “bring in new blood, new ideas and new energy” to steer the country of 6 million people. His latest shake-up beats that of predecessors Lee Hsien Loong (李顯龍) and Goh Chok Tong (吳作棟), who replaced 24 and 11 politicians respectively
Young women standing idly around a park in Tokyo’s west suggest that a giant statue of Godzilla is not the only attraction for a record number of foreign tourists. Their faces lit by the cold glow of their phones, the women lining Okubo Park are evidence that sex tourism has developed as a dark flipside to the bustling Kabukicho nightlife district. Increasing numbers of foreign men are flocking to the area after seeing videos on social media. One of the women said that the area near Kabukicho, where Godzilla rumbles and belches smoke atop a cinema, has become a “real
‘WATER WARFARE’: A Pakistani official called India’s suspension of a 65-year-old treaty on the sharing of waters from the Indus River ‘a cowardly, illegal move’ Pakistan yesterday canceled visas for Indian nationals, closed its airspace for all Indian-owned or operated airlines, and suspended all trade with India, including to and from any third country. The retaliatory measures follow India’s decision to suspend visas for Pakistani nationals in the aftermath of a deadly attack by shooters in Kashmir that killed 26 people, mostly tourists. The rare attack on civilians shocked and outraged India and prompted calls for action against their country’s archenemy, Pakistan. New Delhi did not publicly produce evidence connecting the attack to its neighbor, but said it had “cross-border” links to Pakistan. Pakistan denied any connection to