Intrinsic and extrinsic factors in the dynamics of local small-mammal populations

• Published in: Canadian Journal of Zoology
• Main Authors: Solonen, T., Ahola, P.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Canadian Science Publishing 2010
• Subjects: Animal Science and Zoology; Ecology, Evolution, Behavior and Systematics; North Atlantic; North Atlantic oscillation
• Online Access: http://dx.doi.org/10.1139/z09-138; http://www.nrcresearchpress.com/doi/full-xml/10.1139/Z09-138; http://www.nrcresearchpress.com/doi/pdf/10.1139/Z09-138

We studied dynamics of local small-mammal assemblages consisting of shrews, voles, and mice by small-scale snap trapping in each spring and autumn from 1981 to 2006 in southern Finland. Our aim was to search for relative roles of possible regulatory associations within and between species, as well as to find reflections of the effects of large-scale climatic phenomena on local populations. Preceding intraspecific densities had a dominating role in seasonal changes in small-mammal numbers. Their relationships with weather-related factors indicated by the indices of the North Atlantic Oscillation (NAO) were most pronounced during winter. Relationships with the NAO indices, increasing values of which indicate milder weather in the north, were negative in voles but positive in shrews and mice. Spring densities were governed by the largely compensatory effects of the growth rate of the preceding summer and subsequent population decline during winter in the field vole ( Microtus agrestis (L., 1761)) and mice, while the effects of winter decline dominated in shrews. The bank vole ( Myodes glareolus (Schreber, 1780) = Clethrionomys glareolus (Schreber, 1780)) showed decreasing winter decline, which had a considerable positive effect on population densities.