This news release is also available in French.

New findings suggest that a special combination of predators can drive lemming populations through a four-year boom and bust cycle, which has been one of ecology's big mysteries for over half a century.

While it's a myth that lemmings hurl themselves en masse over cliffs, the reality has been nearly as bewildering for Scandinavians and others at northern high latitudes who periodically find the land awash in these small rodents. Depending on the species, populations of lemmings and their vole cousins can explode by 100 or even 1,000 times their original size and then crash on a regular basis.

The collared lemming, which lives in the high-arctic tundra, is the single prey in one of the world's simplest vertebrate predator-prey relationships. The stoat, arctic fox, snowy owl, and a seabird called the long-tailed skua all dine on this hamster-like animal.

Scientists now suggest that these four predators may be solely responsible for the four-year population cycle in eastern Greenland and possibly in many other collared lemming populations. In contrast to previous hypotheses, food or space shortages didn't appear to be involved, the researchers report in their study, which appears in the 31 October issue of the journal Science, published by AAAS, the non-profit science society

"This question of lemming cycles has been open for almost a century. Different schools have argued about this. It has been a very, very hot issue," said study author Olivier Gilg of the University of Helsinki in Finland and Center for Biology and Management of Populations (CBGP), in Montferrier, France.

The field of small mammal ecology was born in 1924, when the eminent British ecologist Charles Elton published one of his seminal papers on rodent population cycles. Researchers have been studying these cycles ever since
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Contact: Christina Smith
ccsmith@aaas.org
202-326-7088
American Association for the Advancement of Science
30-Oct-2003