The movements of small mammals within the environmental mosaic of a railway junction

Abstract

This study investigated small mammal movements within and between semi isolated habitat islands. The results are relevant to urban small mammal species in general and their movements in relation to man-made barriers in particular. The study site was a railway junction consisting of railway tracks of different widths, dissecting an area of relict grassland in an otherwise urban environment.For two years the small mammals in this area were trapped, marked and recaptured. They were also tracked using dyed bait markers and a grid of dropping boards from which were recovered faeces containing remains of the dyed bait. The ability of the small mammals present (Apodemus sylvaticus, Clethrionomys glareolus and Microtus agrestis) to cross the railway lines was correlated with weight and sex; and also related to the width of the railway track and the vegetation on either side.Conclusions were reached concerning the distribution and behavioural ecology of the three species within the study area, particularly in relation to the animals' capabilities for movement within heterogeneous habitats.The biogeography of small islands such as these was considered, with reference to the effects of size and isolation on mammal movements. The effect of population density on such movements and possible local migratory effects were also investigated. The implications for conservation were discussed and it was shown that information from fieldwork such as this can aid biogeographical analysis in reserve design (for conservation of urban mammal populations) and aid in urban planning.