A comparative study of prey-handling behavior of the Chiwen keelback snake (Rhabdophis chiwen) feeding on earthworms and firefly larvae.

Abstract

Dietary specialists consume specific prey items, and they are often morphologically and behaviorally specialized to feed efficiently on those prey animals. Among specialist snakes, consumption of terrestrial arthropods is relatively rare. Because most terrestrial arthropods possess hardened sclerites and appendages, it is possible that snakes that feed on arthropods would show specialized prey-handling behavior. In this study, we describe prey-handling behavior of a snake feeding on terrestrial arthropods, which hitherto has not been well documented. We focused on Rhabdophis chiwen, which mainly feeds on earthworms, but also consumes lampyrine firefly larvae, sequestering cardiotonic steroids from them in its defensive organs, called nucho-dorsal glands. When feeding on earthworms, snakes showed size-dependent selection of swallowing direction, but this tendency was not observed when feeding on firefly larvae. Manipulation of firefly larvae did not seem to be efficient, probably because they possess sclerites and appendages such as legs that impede smooth handling. Although fireflies are an essential food for R. chiwen as a toxin source, our results showed that the snake is not adept at handling firefly larvae compared to earthworms, implying that dietary specialization does not necessarily accompany behavioral specialization. We discuss possible reasons for this inconsistency.