Cyclicity and stability of grey-sided voles, Clethrionomys rufocanus, of Hokkaido: Spectral and principal components analyses

A spatio-temporal data panel of abundances of the grey-sided vole of Hokkaido (Japan) is analysed. The data consist of annual censuses of 90 populations from 1962-1992. The region studied covers approximately 160 x 220 km. The 90 time series spanning 31 years are analysed using a combination of spectral analysis, principal components analysis and graphical methods. Through this we demonstrate that vole populations in the northwestern coastal region of Hokkaido exhibit seasonal population dynamics, whereas those in the more mountainous northeastern and central regions exhibit multiannual cycles. The multiannual cycles have a period of 3.5-4 years. The findings are related to other studies from Hokkaido as well as studies of North European microtines.