Feasibility of reintroduction of European Bison (Bison bonasus) to Sweden with focus on traffic accidents

Abstract: The historical occurrence of European bison (Bison bonasus) in Sweden during the early Holocene emphasizes the ecological significance for a potential reintroduction. The European bison, the largest herbivore on the European continent, is a keystone species with a significant influence on ecosystem dynamics. To restore populations of European bison is an important conservation concern Road collisions with wild animals are a significant problem on a global scale and an important aspect to consider when large terrestrial mammal populations are restored. This study aims to assess the relative involvement in traffic incidences of European bison and moose (Alces alces) in Poland, where both species occur in the wild. Accidents involving European bison were analyzed and compared with those involving moose during 2014-2022. Four regions were defined and analyzed: Lublin and Subcarpathian provinces; Podlaskie province; Warmian-Masurian province; and Northwest region comprising Lubuskie, Wielkopolskie, and Zachodnipomorskie provinces. The results revealed substantial variations in accident ratios between European bison and moose in different regions. In the Lublin and Subcarpathian regions a significant difference was observed (p = 0.02). The Podlaskie region demonstrated the most pronounced disparity (p < 0.001). In the Warmian-Masurian region, significant differences were again observed (p = 0.003). Conversely, in the Northwest region, no significant difference was found. Overall, the combined analysis across all regions also indicated a highly significant difference (p < 0.001). The overall average accident rate per 100 European bison was 0.49, while for moose it was 1.03. This suggests that moose had a 2.12 times higher accident rate compared to European bison. Additionally, European bison traffic collisions generally result in less severe outcomes compared to moose and other animals, typically causing no fatalities or only minor injuries to drivers and passengers. Considering the relatively low frequency and severity of the traffic collisions, European bison reintroduction efforts may face fewer traffic-related challenges than moose. European bison have demonstrated adaptability across varied landscapes including open areas, forests, and their transitional zones, all of which can be found in southern Sweden. As a generalist grazing species, the dietary requirements of European bison align with available food resources. Climate compatibility is affirmed, as historical and current distribution ranges of European bison encompass regions with more severe climates than southern Sweden. Along with the relatively low risk for traffic incidents as observed in this study, this underline the potential success of reintroducing European bison to the region. Nevertheless, it is important to effectively manage potential conflicts between humans and wildlife. It is advisable to engage in subsequent monitoring and research to gain a better understanding of these challenges during the implementation of reintroduction efforts in a new area.