Studies on the ecology & behaviour of British shrews

Abstract

All five species of British shrews (Sorex araneus, S. minut, Neomys fodiens, Crocidura suaveolens and C. russula were studied with the emphasis being placed on the commoner species. The population dynamics and seasonal fluctuations in numbers of S. araneus and S. ininutus were investigated. A seasonal cycle of captures of S. araneus was demonstrated, with peaks of occurrence in summer, low numbers in winter and a re-emergence of high numbers in spring. Closer study indicated a great mortality of old adults and. juveniles in autumn which commenced before the onset of harsh weather conditions, but overwintering survival of remaining shrews was high. Home ranges and activity of S. araneus appeared to be reduced in winttc. A study of food availability aid diet of S. araneus, S. ininutus and N. fodiens showed major prey items to include adult coleopterans, insect larvae, araneids, isopods and lumbrlcids which occurred In large numbers throughout the year; no decrease in numbers or biomass of prey was found to account for the decrease in body weight of shrews in autumn and winter aid their apparent decline in numbers. Food consumption of shrews ranged from 4 of the body weight daily for C. suaveolens to i6 for S. minutus, but was not directly related to body weight within a species. Conaurnption by S. araneus was reduced at low temperatures. Studies of fat storage by wild. shrews showed no great seasonal differences, although captive shrews ac.cumirulated fat in warm conditions. Studies on the foraging and burrowing behaviour of S. araneu3 showed that they are generally poor burrowers but that they are able to recover insect pupae buried up to 120mm deep in soil. It is sugges ted. that overwintering shrews adopt a more subterranean existence, spending longer periods in the nest to conserve body heat aid less time foraging. Mortality due to increased. predation in autumn, aid reduced activity on the ground surface probably account for low numbers of captures in winter.