Benefits and challenges of collaborating with volunteers: Examples from National Wildlife Roadkill Reporting Systems in Europe

Daily, a large number of animals are killed on European roads due to collisions with vehicles. A high proportion of these events, however, are not documented, as those obliged to collect such data, only record a small proportion; the police only register collisions that lead to traffic accidents, and hunters only collect data on game wildlife. Such reports disproportionately under-records small vertebrates such as birds, small mammals, amphibians and reptiles. In the last decade, however, national wildlife roadkill reporting systems have been launched, largely working with citizen scientists to collect roadkill data on a national basis that could fill this data gap. The aim of this study is, therefore, to describe for the first time, existing projects in Europe, and the user groups that submit data to them. To give a deeper understanding of such projects, we describe exemplar scientific roadkill reporting systems that currently exist in Austria, Belgium, Czechia and the United Kingdom. We define groups of people who contribute to such citizen science activities, and report our experience and best practice with these volunteers. We conclude that volunteers contribute significantly to collecting data on species that are not typically recorded in official databases. To ensure citizen-science projects perpetuate, (I) volunteers need to be motivated by the organisers to participate on a long-term basis, (II) volunteers need support in identifying roadkill species where required, and (III) regular feedback is required on how their contribution is used to produce new scientific knowledge.