Effects of roads on brown bear movements and mortality in Slovakia

The increasing development of road infrastructure considerably contributes to bear habitat fragmentation. The aim of this study was to examine the relationship between brown bear movements and secondary roads. The 1463-km² study area in the north-central Slovakia was defined by the composite home ranges (minimum convex polygon (MCP) 100%) of 21 bears studied by GPS telemetry from 2008 to 2016. Additionally, we used the data of 35 bears struck by cars and trucks across all of Slovakia during 2007–2015. We found that a traffic volume exceeding 5000 vehicles per 24 h completely restricted the movement of bears. Bears were more likely to cross during periods of low- rather than high-traffic volumes, and crossings occurred primarily at night. Males were able to cross roads with annual average daily traffic up to 5000 vehicles per 24 h, whereas females were only able to cross roads with less than 4000 vehicles per 24 h. Bears, regardless of age and gender, crossed roads more frequently during hyperphagia (August to November) than during the mating season (April to July). This was additionally confirmed by the comparison of annual patterns of crossings and road kills, which both peaked in August. The movement of these bears across roads was particularly motivated by the search for attractive crops in fields. Road crossings and road kills mainly occurred around midnight. Understanding the temporal and spatial use of roads by brown bears should provide valuable information for land use planners to effectively minimise the negative impacts of roads on bears.