Rodent fluctuations in relation to seasonality in Fennoscandia and Hokkaido

摘要

For researchers studying population cycles in Fennoscandian small rodents, it is reassuring that a new gradient in fluctuation patterns has been detected in Hokkaido. Differences in fluctuation patterns have indeed been observed in many regions both in the northern and southern hemisphere; however, a distinct gradient has remained restricted to northern Europe until now. It is probably because there have been few other regions with such extensive studies of small rodents as in Fennoscandia and in Hokkaido. In both regions the level of fluctuations, or 'cyclicity', has increased from temperate to boreal or subarctic conditions. The gradient covers a longer distance in Fennoscandia and reaches higher levels of fluctuations ('real cycles' over a larger region).