Аннотация:Common shrews (Sorex araneus) were trapped on study grids located in mixed deciduous forests of western Siberia and 60 km west of Moscow. The patterns of seasonal changes in masses of body, brain, and brain regions were similar in both populations, but there were some differences in absolute values. The regions of the brain differed in their responses to winter and drought conditions by showing greater variation in the phylogenetically recent regions (such as neocortex) than in the phylogenetically ancient regions of the brain, such as olfactory bulbs and myelencephalon. Water content decrease was not the only reason leading to brain size decrease over winter. Dry mass of the brain declined in this period, primarily because forebrain mass declined by 21 % (neocortex especially, 28%). During a period of mass gain in spring the most considerable increase was observed in the hippocampus (+33 % of wet mass, +26% of dry mass). The most noticeable mass changes occurred in this region and only as reproductive activity began. My research indicates broad macromorphological variability occurs in the brain of the common shrew. This variation is associated with age, sex, and different environmental factors such as geographic, seasonal, and extreme climatic (summer drought) parameters. The possibility is explored that seasonal (and other) variation in brain mass (previously reported by this author for voles) may represent a more generalized mammalian pattern of adaptive mechanism of winter-active small mammals employed to conserve
energy during harsh climatic conditions.