Individual use of wildlife underpasses by small mammals: what about gene flow?

Abstract

Landscape fragmentation, caused by linear infrastructures answering human needs, has strong ecological consequences by genetically isolating animal populations and causing their decline. In order to reconnect populations on each side of the road, wildlife-crossing structures are built but their effectiveness on an individual scale for small mammals' dispersion is unknown. A Capture-Mark-Recapture method has been performed on the wood mouse (Apodemus sylvaticus) and on the common vole (Microtus agrestis) in road verges of road sections with and without wildlife underpasses. The dispersion probability between the two sides of road sections was deduced. A partial restoration of ecologic connectivities through wildlife crossings was revealed as recaptured individuals only crossed sections equipped with wildlife underpasses. However, the dispersion probability by crossing the road may be too low to ensure a sufficient genetic flow. From a perspective of species conservation, it is necessary to enhance these structures to be more adapted to target species like small mammals and thus optimize the crossing probabilities and restore a sufficient genetic mixing between separated populations.