Dolichophis caspius road mortality at its northern distribution range limit: the lower Olt River valley, southern Romania

Dolichophis caspius is frequently affected by road mortality, with many victims recorded also in Romania. Although some regions in the country have a presumptive high risk of road mortality, there is no certain data from all regions. In 2021 and 2024, we analyzed this species’ road mortality at its northern distribution range limit (lower Olt River valley, southern Romania). We identified 66 road-killed D. caspius over the course of eight days. Most victims (62.12%) were juveniles. The high number of road-killed juveniles is a consequence of the road`s features, which crosses many small human settlements (villages) and has numerous curves and speed enforcement cameras; therefore, the speed is reduced to 50 km/h. Consequently, the small-sized road-killed juveniles were easier to observe, as compared to roads of higher speeds, where they can be easily missed. The high number of juveniles indicates that in the region there are large populations that reproduce, as they are probably favored by climate warming. Although the absolute number of road-killed juveniles was higher at the end of summer and autumn, the ratio of juveniles and adults was the same in spring. The differences in road mortality on different days, even of the same month, indicate the importance of local microclimate conditions for the activity and road mortality of D. caspius . The lower Olt River valley region has a high risk of road mortality for this species, as it shows the scale of this phenomenon by highlighting the impact on juveniles.