Understanding Roadkill Hotspots: Insights from Comprehensive Wildlife Roadkill Databases

Abstract

Wildlife roadkill databases often compile valuable information regarding species, timing, and locations of roadkill incidents, with some databases also including details such as gender and age classes. As part of the “LIFE LINES - Linear Infrastructure Networks with Ecological Solutions” project, we aggregated roadkill data from various sources, including road operators, traffic police, and academic institutions, into the Portuguese National Roadkill Database. This database encompasses over 130,000 records spanning most terrestrial vertebrates found in the country, ranging from small (< 1 kg) to medium (1-10 kg) and large (> 10 kg) species. Different sources contribute varying data, with academia accounting for all species and sizes, road operators primarily documenting medium and large vertebrates, and traffic police focusing mostly on large vertebrates. Notably, different data sources yield distinct roadkill hotspot patterns. By analysing a specific subset of the database consisting of daily monitored roadkill incidents, we investigated how different monitoring intervals affect the frequency and location of hotspots across various vertebrate classes, orders, species, and size categories. Our findings reveal that for smaller species like bats and amphibians, sampling intervals exceeding one day result in contrasting patterns compared to daily sampling, while for most medium and larger species, such discrepancies occur primarily with sampling intervals exceeding one week. We discuss the implications of these results for the development of effective roadkill monitoring and mitigation initiatives.