Wildlife mortality on the Slovenian highways: monthly patterns, identification of hotspots and effectiveness of acoustic deterrents

We studied species composition and monthly patterns of roadkill of large and medium sized mammal species along 778 km of Slovenian highways in the period 2018–2020. Apart from providing the first comprehensive data on monthly patterns of roadkill as a proxy of wildlife-vehicle collisions at Slovenian highways and identifying linear collision hotspots (using KDE + methodology), we also tested the impact of acoustic deterrents installed at highway interchanges in late 2018 on WVC frequency. In the three-year period, we registered in total 2046 roadkill cases, with red fox (Vulpes vulpes), (N = 790; 39.6%), roe deer (Capreolus capreolus) (N = 592; 28.9%), and European badger (Meles meles), (N = 423; 20.7%) being the most exposed species. Temporal collision patterns with evident species-specific monthly peaks reflect the behaviour and activity of these three species. We identified 268 KDE + hotspots, accounting for 48.5% of all roadkill and covering 9.3% (72.6 km) of the highway network. Recognising these hotspots is crucial for implementing mitigation measures to reduce WVC on Slovenian highways. However, our findings indicate no decrease in roadkill after installation of acoustic deterrents (2019–2020), therefore additional effort is needed to find adequate and effective approach for reducing roadkill and hence increasing road safety.