SMALL MAMMAL POPULATIONS IN RELATION TO HEDGEROW STRUCTURE IN AN ARABLE LANDSCAPE

The population ecology of small mammals in hedgerows in arable farmlan d in eastern England is described. Features of hedgerows of importance to individual species are examined. Some 97% of the total 3042 mammal s captured were wood mouse Apodemus sylvaticus, yellow-necked mouse Ap odemus flavicollis, bank vole Clethrionomys glareolus and common shrew Sorer araneus. Small numbers of harvest mice Micromys minutus, field voles Microtus agrestis, pygmy shrews Sorer minutus and water shrews N eomys fodiens were also caught. Wood mouse, the most numerous species, showed a typical pattern of large numbers in autumn and winter, follo wed by a simultaneous decline over all hedges in early spring. Populat ion changes were less clear in yellow-necked mouse and bank vole but t he yellow-necked mouse was more scarce in the second year of study. Co mmon shrews were must numerous in summer and declined rapidly in autum n. Hedgerow coppicing had a marked effect on yellow-necked mouse numbe rs but not on wood mouse. In an extensive survey of mammal numbers in relation to hedgerow features, ground cover was found to be the single largest factor influencing size of bank vole populations. Hedgerow co ndition (lack of gaps) was important to yellow-necked mice, which thri ved only in well-established hedgerows. Wood mice appeared little infl uenced by the characteristics of the hedge. Common shrews were more ab undant in hedgerows with adjacent permanent water.