Differences in prey-handling behavior of earthworm-eating snakes between a specialist and a generalist

Predators are generally classified into two types based on feeding strategies: dietary specialists and generalists. Specialist predators exhibit prey-handling behaviors adapted to specific prey types. In snakes, earthworm-feeding has evolved independently multiple times, resulting in the presence of both specialists and generalists among earthworm-eating species. Nevertheless, studies on prey-handling behavior of earthworm-feeding snakes remain limited. We compared prey-handling behavior of two colubrid snakes, an earthworm-feeding specialist, the Ryukyu green snake (Ptyas semicarinata) and a generalist, the Japanese keelback snake (Hebius vibakari), by feeding them earthworms. Ptyas semicarinata swallowed earthworms with minimal lateral jaw movements and exhibited significantly shorter prey-handling time than H. vibakari. The swallowing behavior of P. semicarinata partially differed from typical jaw-walking and is likely an adaptation to earthworm prey. The movements of the earthworms appeared to facilitate ingestion in P. semicarinata. Future studies employing CT imaging and functional analyses of cranial morphology may help elucidate the mechanisms underlying this rapid swallowing behavior.