Seasonal Changes in the Braincase of Some Representatives of the Genus Sorex from the Palearctic

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Abstract
Seasonal changes, expressed by a reduction in height of skull in winter by 17%, were found in Sorex araneus from the Soviet Union, Bulgaria and Czechoslovakia. This finding therefore confirms the existence of the phenomenon described by Dehnel (1949) and extends its known occurrence to the whole geographical range of this species. The occurrence of winter flattening of the skull in S. caecutiens was established. It was found that this phenomenon occurs in other species of the genus Sorex also, that is, in S. arcticus, S. unguiculatus and S. vir, and that it most probably occurs in S. asper and S. raddei. The same seasonal changes have been found in S. minutus (Dehnel, 1949; Kubik, 1951). Differences in the course taken by seasonal changes in the skull in different parts of the geographical range of S. araneus in Central and Eastern Europe were found. The greatest differences in the height of the braincase in specimens from summer and winter can be observed in shrews from the Soviet Union (about 17%) and the smallest in specimens from northern Germany (11%). This variation may be caused by the different climatic conditions.