Impact of a road on the movements of two ground beetle species (Coleoptera: Carabidae)

We studied the effects of a road on the walking directions of the carabid species Poecilus versicolor and Agonum sexpunctatum. Using mark and recapture experiments and window traps we determined the number of road crossings and the deviation in walking directions caused by the road. We found two effects of the road on the walking behaviour: (1) the road is a barrier to both species, but whereas P versicolor was reluctant to cross the road and had a significant movement away from the road, we recorded no road crossings by A. sexpunctatum; and (2) A. sexpunctatum showed a marked tendency to walk along the roadside verge, particularly in the ditch. Of these two species, only one individual of A. sexpunctatum was caught flying close to the road, indicating that it might cross the road by flying. Counts of dead carabid specimens on two 100 m long transects along the road carried out for nine weeks recorded several individuals of P versicolor. We conclude with suggestions on how to implement the results of this study in nature conservation practices.