Trophic consequences of pelagic life-style in yellow-bellied sea snakes

Abstract

Snakes show a close relationship between their own size and that of their prey. This is especially true for marine species that forage on the sea floor. In these sea snakes, body size influences both the depth to which a snake dives and its ability to extract prey from crevices in which they shelter. These factors could be expected to have less influence in the case of strictly pelagic foragers. We examined the trophic ecology of the yellow-bellied sea snake Pelamis platurus, which is the only surface-feeding sea snake species. We based our study on 2 independent but complementary datasets: dietary data and stable isotopes. Our results confirm the pelagic trophic ecology of this species. However, in contrast to other marine species, P. platurus does not exhibit any ontogenetic shift in prey size despite having a relatively large range of body size. Although prey number increases with a snake's size, our results suggest a limitation on P. platurus' ability to accommodate very large prey. Functional attributes that are linked to a pelagic life-style such as swimming performance, buoyancy regulation, and osmoregulation-in addition to possible limitations of prey availability-are likely to constrain the trophic ecology of this species. Future investigations should explore the relative contributions of these different, but not mutually exclusive functional attributes, to unravel the foraging constraints in the context of evolutionary transition to marine life in secondarily marine vertebrates. © Inter-Research 2013.