The Ecology of Small Mammals in Urban Habitats. I. Populations in a Patchy Environment

Abstract

Populations of four species of small mammals, Apodemus sylvaticus, Clethrionomys glareolus, Microtus agrestis and Sorex araneus, were censused using live traps and hair sampling tubes in fifty discrete patches of habitat within the City of Oxford (England UK). Habitats were classified as woodland, scrub, orchard, long grass, short grass, allotment, detached, and semi-detached house garden using ordination methods and subjective criteria. Apodemus sylvaticus occurred in all habitats and in 84% of patches, and reached maximum densities (c. 70-80 ha-1) in scrub. Clethrionomys glareolus occurred in all habitats except allotment, and achieved maximum abundance (< 30 ha-1) in woodland. Microtus agrestis and Sorex araneus were largely absent from cultivated gardens, allotments and short grass, and were most abundant (c. 50-66 ha-1) in long grass and scrub. The densities of all species were strongly influenced by the density of vegetation at particular heights above ground, and more weakly by indexes of habitat modification and urban disturbance. The results indicate that small mammals do not perceive the urban environment directly, but respond to it indirectly if it modifies the growth or structure of patch vegetation.