Studying boundary effects on animal movement in heterogeneous landscapes: the case of Abax ater (Coleoptera: Carabidae) in hedgerow network landscapes.

Changes in movement possibilities of insect species can be a response to increasing heterogeneity in man made landscapes. We studied the movement of Abax ater (Coleoptera, Carabidae) between woody and cultivated areas in Brittany. Two woody habitats (woods and hedgerows) and two cultivated areas (cornfields and meadows) were considered. Quantifying the movement of the carabid beetle between woody and cultivated areas was done using Mark-Release-Recapture techniques. Marked individuals were released at the centre of circular enclosures (3 m in diameter), encompassing two adjacent habitats, one being wooded, the other cultivated. Individuals were recaptured at the edge of enclosures. Analysis of recaptures showed that flows of individuals from a given habitat to another were constant during the experiment. Flows can be summed up by a probability of move, which depends on the two adjacent habitats surrounding ecotone. When released in cultivated habitats, forest carabid beetles preferentially moved toward woody habitat, but in some enclosures the forest carabid beetles did not exhibited any preference between cultivated areas and woods. In these cases ecotones may include both woody and cultivated areas, and their functional width should be reconsidered. These conclusions were globally in agreement with knowledge about ecology of Abax ater, but ask for confirmation through replicates on different sites. Nevertheless, these results demonstrated the usefulness of the method and give new guidelines for the study of flows of carabid beetles through ecotones.