COMMUNITY STRUCTURE AND HABITAT USE OF SMALL MAMMALS IN GRASSLANDS OFDIFFERENT SUCCESSIONAL AGE

The use of habitat by eight species of small mammals was investigated by live-trapping and mark-recapture techniques in a series of eight gr assland plots of different successional age, ranging from 11 months to 10 years at the start of the study, in southern England. Vegetation c omposition and structure in the grassland plots was investigated by po int quadrat and biomass methods. Species richness ranged from 5-6 per plot. The harvest mouse, Micromys minutus, was a relative specialist t hat dominated the ruderal stage with its abundant annual and perennial forbs, and was absent from the mid-successional stage. The wood mouse , Apodemus sylvaticus, was also a relative specialist, but dominated t he opposite end of the successional gradient (the mid-successional sta ge. with its small trees and shrubs), and occurred infrequently on the ruderal plot. The common shrew, Sorex araneus, pygmy shrew, S. minutu s and field vole, Microtus agrestis were relative generalists with no clear habitat preferences. S. araneus was numerically dominant on most plots and was abundant even on the ruderal plot. The mid-successional stage sustained the greatest total number of small mammals, but the r uderal plot was also well populated. Niche overlap was greatest betwee n the shrews and least between A. sylvaticus and M. minutus. Despite s ome preferences for mid-successional stages, all species were rapid co lonizers of the ruderal plot: first to be captured regularly were M. m inutus and A. sylvaticus, followed by the shrews and M. agrestis, all within 1-2 years of establishment of the plot.