Tracking past and ongoing lemming cycles on the Eurasian tundra

During the Swedish-Russian Tundra Ecology -94 expedition one of the goals was to describe the local population fluctuations of Siberian lemmings over the Eurasian tundra. In order to compensate for the lack of repeated sampling, we used 4 different estimates to determine the phase position of the lemming populations at the different sites: i) the number of lemmings trapped per unit time; ii) the age structure of the lemming population; iii) the level of chemical defences in important food plants; and iv) the age distribution of microtine scars on willow stems ('a historical archive' on past lemming fluctuations on the site). We present data from 4 of the 12 sites investigated. The 4 different approaches gave, to a large extent, coherent results. We suggest that our combined approach may be useful when sampling is possible during 1 year only, but we strongly recommend that the sampling is done at the same phenological stage at all the compared sites. Data reported here and elsewhere by us, indicate that the local populations of Siberian lemmings do not show synchronous dynamics over the vast Eurasian tundra.