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2 Acta Theriologica

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Relative growth and annual size variation in Crocidura russula from the Ebro Delta Spain

100%

Lopez-Fuster M. J. , Ventura J.

Acta Theriologica

1992

tom 37

nr 4

We report data on the somatometry of the white-toothed shrew Crocidura russula (Hermann, 1780), based on 302 specimens (153 males, 149 females) captured between 1980 and 1982 in the Ebro Delta (northeastern Spain). Variations in body size and weight were analysed according to sex, relative age (estimated by tooth wear) and month of capture. Relative and seasonal growth were also studied. No statistical difference in body size was detected between sexes. The specimens showed highest growth rate up to about fourteen weeks of age. Afterwards, most of the variations detected in body length and especially in weight were basically related to sexual stage. Specimens born in the first litters of the year grew faster than those born at the end.

Range expansion of the greater white-toothed shrew Crocidura russula in Switzerland results in local extinction of the bicoloured white-toothed shrew C.leucodon

80%

Vogel P. , Jutzeler S. , Rulence B. , Reutter B. A.

tom 47

nr 1

The distribution limits of Crocidura russula (Hermann, 1780) and C. leucodon (Hermann, 1780) were investigated during an interval of 25 years in the bottom of the Rhone valley above Lake Geneva, Switzerland (total data set: 105 spatio-temporal occurrences, 1137 shrews). In 1975, the contact zone between the two species was situated in the region of Martigny. In 1999/2000, new sampling revealed three results: (1) The contact zone showed an upward shift of about 25 km. (2) In the expanded range of C. russula, the resident species has totally disappeared (confirmed by owl pellets analysis). (3) This demonstrates a dominance of C. russula over C. leucodon. Three hypotheses which may explain the range expansion of C. russula were evaluated: (1) habitat modification favouring linear dispersal due to the construction of a highway; (2) temporal event favoured by climate fluctuations, or (3) ongoing postglacial colonisation of Europe. Hypothesis 1 was rejected, because the progression of the shrews anticipated the construction. Hypothesis 3 received only weak support because range limits of C. russula in the region of Nice have been stable for thousands of years. Therefore hypothesis 2, admitting that ongoing climate change has facilitated range expansion, is the most probable.