VINCENT, S/E; MOON, B/R; HERREL, A; Tulane Unversity; University of Louisiana at Lafayette; University of Antwerp Universiteitsplein 1 : The functional meaning of “prey size” in snakes: influence of prey dimensions on feeding function and performance in water snakes (Nerodia fasciata)

The evolutionary success of macrostomatan (enlarged-gape) snakes has been attributed to their ability to consume large prey via their highly kinetic skulls. However, prey can be “large” in several ways, and we have little insight into which aspects of prey size and shape affect skull function during feeding. We used X-ray videos of broad-banded water snakes (Nerodia fasciata) feeding on frogs and fish to quantify movements of the jaw elements during prey transport, and of the cervical system during post-cranial swallowing. In a sample of additional individuals feeding on frogs and fish, we measured the time and the number of mandibular protractions needed to transport prey through the buccal cavity. Prey type did not influence transport kinematics, but relatively wider and shorter prey induced greater movements of most cranial elements, and significantly less cervical bending. In contrast, heavier, shorter, and wider prey took significantly more time and a greater number of mandibular protractions to ingest. Thus, the functional challenges involved in prey transport depend not only upon prey mass, but also prey type and prey shape, suggesting that the difficulty of prey ingestion for a gape-limited predator depends upon more than simply prey size.