Boffins: global warming kills lemmings, not suicide

Norwegian rodents dying against will

The Norwegian lemming population is dwindling - through no fault of its own.

According to a report published in the science journal Nature, lemming numbers are shrinking thanks to rising temperatures brought on by global warming, putting an end to the population peaks and valleys that have traditionally characterized the species. "The lemming population is falling and the peaks are disappearing," Oslo University's Nils Stenseth, one of the authors of the study, told Reuters.

In the past, the lemming population has peaked and valleyed every three to five years - a cycle that gave rise to the widely held belief that lemmings like to kill themselves. But according to Stenseth, the last peak hit in 1994.

Warmer temperatures, he says, have eliminated gaps under powdery Norwegian snow where female lemmings have historically hidden and fed their litters in early spring.

With the lemming peaks disappearing, predators are forced to turn elsewhere. "A relatively small effect on one particular species is having a broad effect on the system," Stenseth said. "Now when the lemming peak is gone...they will prey on other species such as ptarmigan and grouse."

And if there's no peak, there's no valley. Past population booms meant food shortages for the lemmings themselves, driving some to desperation."On occasion, desperate to find food, they jump into water and start swimming. This behavior led to the myth that lemmings commit suicide," said Tim Coulson of Imperial College, London, in a commentary on the Nature study. ®