We investigated diet breadth and diet overlap in three sympatric snakes of similar body size: Dekay’s Brownsnakes (Storeria dekayi), Red-bellied Snakes (S. occipitomaculata), and sub-adult Common Gartersnakes (Thamnophis sirtalis), by examining recently consumed prey (n = 388) collected from wild-caught snakes (n = 263) in northern Illinois. Storeria occipitomaculata were dietary specialists, feeding nearly exclusively on slugs. Storeria dekayi fed predominately on slugs but also consumed snails and earthworms. Sub-adult T. sirtalis fed predominately on earthworms but also consumed frogs and small mammals. Diet overlap was extensive between Storeria species but relatively low between Storeria and Thamnophis. It is noteworthy that the two most abundant prey types, slugs and earthworms, are non-native. These non-native prey occur in high numbers, which may ameliorate competitive interactions and influence grassland snake abundance and persistence regionally
