The highway section between Vrhnika and Postojna on the A1 motorway crosses an environmentally important area and its location represents an ecological barrier for wildlife species between the Alps and Dinarides. The studied area is habitat of all carnivore species which are protected in Slovenia: brown bear, wolf, Eurasian lynx, and wildcat. Using camera traps, we monitored eight highway crossings, built for forest management and not designated wildlife ecoducts in the area of Menišija and Javorniki. We observed individual crossings from four to 66 days. We analyzed camera trap data and measured or assessed the technical and environmental factors of these crossings. We recorded crossings of eleven animal species, including all protected large carnivores. In contrast to previous research, we did not find a significant impact of environmental factors (dimensions, visibility, coverage, ruggedness, forest type, and forest age class) on the frequency of crossings. We also did not observe an impact on crossing frequency based on crossing type (overpass, underpass) or crossing area (Menišija, Javorniki). Whereas we did not identify significant differences in crossing frequency between the Javorniki and Menišija areas, we did find differences in species diversity between these areas. We documented 11 different species in the Menišija area and only six in the Javorniki area, albeit with fewer crossings in the latter. A significant influence of human presence on animal crossings was observed for small carnivores. They use crossings less frequently in areas with higher human presence. The time of day also has a significant impact on crossings, with animals using the highway most frequently during the night, when human presence is minimal. The divergence from the majority of previous research results is likely due to methodological limitations (short monitoring periods, a small number of monitored objects, selected variables under scrutiny). An ecoduct is planned in the Javorniki area. Based on the results of our and previous studies, it will be important to restrict human presence both on and around the ecoduct.
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