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CR 32:109-118 (2006)  -  doi:10.3354/cr032109

Effects of regime shifts on the population dynamics of the grey-sided vole in Hokkaido, Japan

Takashi Saitoh1,*, Bernard Cazelles2,4, Jon Olav Vik3, Hildegunn Viljugrein3, Nils Chr. Stenseth3

1Field Science Center, Hokkaido University, North 11, West 10, Sapporo 060-0811, Japan
2Centre Nationale de la Recherche Scientific-Unité Mixte de Recherche (CNRS-UMR), 7625, Ecole Normale Supérieure, 46 rue d’Ulm, 75230 Paris, France
3Centre for Ecological and Evolutionary Synthesis (CEES), Department of Biology, University of Oslo, PO Box 1066 Blindern, 0316 Oslo, Norway
4Institute de Recherche pour le Développement (IRD), Unité de Recherche (UR) GEODES, 32 avenue Henri Varagnat, 93143 Bondy, France

ABSTRACT: We explored the effects of regime shifts (drastic changes usually observed in marine ecosystems, corresponding to climatic variability) in a terrestrial system focusing on a key event that occurred in 1976-77. We used data on the gray-sided vole Clethrionomys rufocanus (Sundevall, 1846) from 89 time series covering 31 yr (1962–1992), recorded in Asahikawa, Hokkaido, Japan, where both cyclic and non-cyclic populations occur. Wavelet analyses demonstrated a clear shift of dynamic patterns in the mid-1970s, presumably resulting from the Aleutian Low Pressure (as measured by the Aleutian Low Pressure Index). The vole populations exhibited erratic fluctuations until the mid-1970s, and then changed their pattern to cyclic fluctuations at a 4 yr interval. The structure of density dependence changed during the regime shift. Although the strength of direct density dependence was similar, delayed density dependence became stronger after the shift. Altogether these findings suggest that changing climate may affect the ecological interactions among voles, predators and resources.

KEY WORDS: Aleutian Low Pressure · Clethrionomys rufocanus · Cycle · Density dependence · Hokkaido

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