Population dynamics and the seasonal fluctuations in numbers of the common shrew in Britain

Abstract

Common shrews, S. araneus Linnaeus, 1758, were trapped in scrub-grassland at Monks Wood, (Cambridgeshire) and in deciduous woodland at Alice Holt Forest (Surrey, England) for 28-34 mo. to provide information on seasonal numbers, survival, life expectancy and activity and movement. A seasonal cycle in numbers of captures was revealed, with high numbers in summer and low numbers in winter. Mark-recapture data revealed that only 50% of shrews survived the first 2 mo. of life but over 80% of the survivors successfully overwintered; 20-30% of shrews survived to breed. Population density estimates, based on monthly captures, are greatly underestimated in winter. Mark-recapture studies showed that activity and movement were greater in spring and summer but were much reduced in winter. Reduced activity on the ground surface may explain the low numbers of captures in winter, and may be a strategy to assist overwintering survival by reducing heat loss.