Roads can generate high rates of animal mortality because causalities with vehicles, and changes in the structure and composition of biotic communities because edge effects, pollution and/or disturbances associated to traffic. However, nothing has been published about such effects in ecosystems of Colombia, and little in Neotropical ecosystems. Along six months (February to July of 2006) we studied the mortality of vertebrates due to vehicular casualties in a segment of 2.4Km of the Buga-Buenaventura road, which crosses the Forestal Reserve Bosque de Yotoco, a fragment of sub-Andean forest in Western Andes of Colombia. In addition, we recorded the composition and structure of herpetofaunal and avifauna assemblages from areas closer to the road toward areas away from the road (forest-interior). For herpetofaunal surveys we performed a sampling of 172 hours/man in 28 plots of 15 x 15m each (225m2). Plots were distributed close to the road (14 plots, seven at each margin of the road) and in areas of forest-interior (seven in each of the two fragments within the study area). For birds, visual census (168 hours of sampling) and mist-nets surveys (192 hours/net) were conducted in 21 sampling stations, seven along road margins and seven in the interior of each forested fragment of the study area.
Results/Conclusions
We recorded 49 dead vertebrates on the road, with a mortality rate of 3.59, one vertebrate each 3-4 days. Almost 50% of these carcasses were snakes probably because they look for warm substrates for thermoregulation such as the road surface. The richness of amphibians was higher in areas of forest interior (seven species) than in areas closer to the road (four species), while reptiles exhibited an opposite pattern (eight against twelve species). 1844 birds belonging to 99 species were recorded and the community of species changed between areas adjacent and away from the road. Our results suggest that variations in the structure and composition of amphibians and reptiles can be a consequence of alteration in microclimatic characteristics and vegetal complexity in areas closer to road, but other factors are not discarded (e.g. pollution). Variation in avifaunal was attributed principally to acoustic disturbances produced by vehicular traffic on the road (up to 64.1 dB noise) and colonization of forest edges by birds of open habitats coming from lower altitudes. Some populations of vertebrates, especially those of forest interior, can be fragmented due to disturbances associated by road effects.
