Influence of roads on movements of small mammals.

The landscape of the world is becoming more dissected by roads each year du e to the growing human population. Numerous studies have documented the dir ect impact of roads on wildlife by examining mortality caused by vehicles b ut few have investigated indirect effects of roads on animals. We used capt ure-mark-recapture (CMR), fluorescent pigments, and radiotelemetry techniqu es to assess the influence of roads on movements of rodents. During CMR, on ly 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 w hen 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% o f all locations were on the same side as the original capture for all indiv iduals. Roads were partial barriers to movements of rodents; however, when displaced, animals exhibited a greater likelihood of crossing a road. Altho ugh proportion of rodents crossing roads varied among the 3 studies, all te chniques yielded consistent results.