ROSSELL, John M.; VINCENT, Shawn E.; HERREL, Anthony; IRSCHICK, Duncan J.; Tulane University; Tulane University; University of Antwerp; Tulane University: Do juvenile snakes compensate for their small size when feeding? Ontogeny of feeding performance in the water snake, Nerodia fasciata

When juvenile and adult animals occur syntopically, juveniles are believed to be at a distinct competitive disadvantage due to their absolutely small size. Previous authors have suggested that one way for juveniles to bridge this competitive gap is through increased ecological performance (compensation hypothesis). This hypothesis is particularly relevant to feeding biology, as many age and size classes are known to directly compete for food. Nonetheless, only a handful of studies have tested whether juvenile animals have increased feeding performance (e.g., decreased ingestion and/or handling times relative to body size) compared to adults. We tested this hypothesis by examining the ontogeny of head dimensions and feeding performance (ingestion time and number of mandibular protractions) on fish prey for broad-banded water snakes (Nerodia fasciata). Individuals were fed a range of overlapping fish sizes. All head dimensions scaled with significant negative allometry versus body size, and thus juveniles have relatively larger heads for their body size than adults. As snakes are gape-limited predators, this result suggests that smaller snakes should have relatively better feeding performance compared to adults. Contrary to this prediction, however, juveniles had both absolutely (non-size adjusted) and relatively poorer feeding performances (body size adjusted) than adults. Therefore, we suggest that juvenile water snakes do not compensate for their absolutely small size through increased feeding performance.