Influence of roads on movements of small mammals.

The landscape of the world is becoming more dissected by roads each year due to the growing human population. Numerous studies have documented the direct impact of roads on wildlife by examining mortality caused by vehicles but few have investigated indirect effects of roads on animals. We used capture-mark-recapture (CMR), fluorescent pigments, and radiotelemetry techniques to assess the influence of roads on movements of rodents. During CMR, only 5 of 53 (9.4%) individuals captured more than once spontaneously crossed roads, whereas 21 of 51 (41.2%) rodents that were displaced across roads when released returned to the side of their original capture. Only I of 54 (1.9%) rodents powdered with fluorescent pigment moved across the road when released at their capture site. In contrast, 7 of 53 (13.2%) displaced and powdered animals crossed the road. Six of 12 (50%) radiotagged animals were located on both sides of the road on at least I occasion; however, > 90% of all locations were on the same side as the original capture for all individuals. Roads were partial barriers to movements of rodents; however, when displaced, animals exhibited a greater likelihood of crossing a road. Although proportion of rodents crossing roads varied among the 3 studies, all techniques yielded consistent results.