Population dynamics and survivorship patterns in the common shrew Sorex araneus in southern England

Results of a four-year, mark-recapture study of a high-density population of Sorex araneus Linnaeus, 1758 inhabiting grassland are reported. The population showed regular cycles of abundance between seasons and differences between years. Captures were not related to ambient temperature or rainfall, and population numbers showed no consistent correlation with winter weather conditions. Immigration and dispersal occurred throughout the year but were lowest in winter. Fifty-five percent of males and 35% of females in the breeding population were immigrants. Shrews underwent an autumn-winter weight loss of 12-19% but there was no evidence that weather conditions affected seasonal or annual patterns of weight change. There were no significant differences in body mass between resident and transient (and dispersing) young or between resident and immigrant adults. Weather conditions affected neither monthly survival, nor annual winter mortality rate which was 21-48%. Onset of sexual maturity was not affected by time of birth, but early-born cohorts had better survival rates at all stages than did late-born cohorts. There were significant differences in survival between cohorts born in different years but these were not correlated with weather conditions or population density.