Explosive Lemming Outbreaks in Fennoscandia

LemmingAn outbreak of lemmings is not something you’ll see every year. The last major one was 2006 to 2007 – the first time in two decades. The causes of, and mechanisms behind, such population surges are, to this day, intriguing naturalists (and physicists, and mathematicians). But some progress towards understanding the outbreaks is, however, being made. A team from the Department of Arctic and Marine Biology, University of Tromsø, Norway, had the good fortune to be carrying out a spatially extensive seasonal lemming-monitoring survey in northern Fennoscandia when there was an explosion (of lemmings). See;’Determinants of lemming outbreaks’ by Rolf A. Ims, Nigel G. Yoccoz, and Siw T. Killengreen, Proceedings of the National Academy of Sciences of the Untied States of America (PNAS), February 1, 2011 vol. 108 no. 5

“Our spatially extensive seasonal monitoring, which happened to encompass the now rare event of a proper lemming outbreak in northern Fennoscandia, allowed us to provide a detailed comparison of the topology of the lemming outbreak with the simultaneous dynamics of the gray-sided vole. In accordance with previous studies the lemming exhibited a steeper increase phase than that of the vole. However, the previous studies based their analysis of population growth rates taken at an annual time scale (fall to fall); i.e., the population dynamics were not separated into seasonal components. In contrast, we analyzed growth rates for summers (spring to fall) and winters (fall to spring) separately and thereby can provide unique insights into the basis for the lemming–vole dichotomy.”

The open-access paper, with maps and graphs, can be read in full here:

Note: Rumours regarding the death of lemmings (by unassisted suicide) appear to have been greatly exaggerated. Here’s a snippet from Wikipedia citing the 1958 Disney film White Wilderness :

“[…] in which staged footage was shown with lemmings jumping into certain death after faked scenes of mass migration. A Canadian Broadcasting Corporation documentary, Cruel Camera, found the lemmings used for White Wilderness were flown from Hudson Bay to Calgary, Alberta, Canada, where they did not jump off the cliff, but were in fact launched off the cliff using a turntable.”

More detail here:


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