The diet of smooth snakes (Colubridae: Coronella) across their range: insights from observations and citizen science data

Citizen science can help gain insight into many scientific fields, including the life history and ecology of organisms. Despite its potential, citizen science is still often neglected in dietary studies, especially in the case of snakes. In this study we collected observations of feeding smooth snakes (Coronella austriaca) and Southern smooth snakes (C. girondica) from various citizen science and social media platforms, as well as from personal and expert observations and identified prey items in them. We found 189 observations across the range of the smooth snake and 47 observations from the Southern smooth snake. Both species consumed mainly reptiles; half of the prey items of the smooth snake were slow worms (51.8%), and it also fed on lacertid lizards (22.2%), colubrid snakes (14.3%), further, we recorded 2 events of viper predation (1.9%). Besides reptiles, smooth snakes also consumed mammals (9.5%), and occasionally birds and Orthopterans (1.0% each). Southern smooth snakes exclusively preyed on reptiles, mainly lacertid lizards (66.0%) and geckos (27.7%), and we also recorded predation on slow worm (4.3%) and colubrid snakes (2.1%). As we found significant spatial clustering in our data, we resampled our dataset to control for spatial bias; resulting in significantly different frequencies for most prey categories, suggesting the importance of spatial bias, however, overall patterns remained similar. We found notable differences after comparing our data to available literature, which can likely be attributed to geographic variation in prey availability. Our study confirms both species as reptile specialist predators and highlights the availability of citizen science data for dietary studies on snakes and also emphasises the knowledge gaps in the diet of smooth snake species.