Effectiveness of crossings as wildlife passages for mammals in the Yungas of Argentina

Abstract

Irrigation canals are an important cause of wild mammal mortality in the Piedmont forest of the Argentine Yungas. To improve the permeability of this infrastructure, specific wildlife crossings were added to the existing non-wildlife crossings built for other purposes. However, the effectiveness of these wildlife-specific crossings has still not been evaluated. Here, we identified the mammalian species that use the crossings, determined the global frequency of use of each crossing through a use index, and evaluated the possible predilection of a species for a particular crossing type using species-specific models. We found that 50 % of species in the study area used the crossings. The highest percentages of use corresponded to tapeti (Sylvilagus brasiliensis, 25.4 %), lowland tapir (Tapirus terrestris, 21.5 %), agouti (Dasyprocta punctata, 20.7 %), crab-eating fox (Cerdocyon thous, 9.1 %) and tayra (Eira barbara, 6.3 %).The global model shows that crossing type, openness and vegetation vertical structure were the best predictors of crossing use. Species-specific models show in general that variables related to the structure of the crossings were better able to explain animal movement. The dry season increased the use of the crossings. We concluded that the presence of both wildlife-specific and non-wildlife-specific crossings would contribute to reducing the barrier effect and, therefore, to mammal conservation. In this connection we recommend that simple, low-cost wildlife-specific crossings be taken into account.