Locomotor performance of three sympatric species of sea kraits (Laticauda spp.) from orchid island, Taiwan

Background: Assuming that locomotion has a strong influence on animals' fitness, we hypothesized that better locomotor performance would be associated with the most frequently utilized habitat. Laticauda colubrina, Laticauda laticaudata, and Laticauda semifasciata have different amphibious habits and microhabitat preferences at Orchid Island, Taiwan. We investigated the morphology and locomotor performance of the three sympatric species of sea krait. The measurements of body size, tail area, and body shape were compared in our study. Data on crawling and swimming speeds were gathered to investigate locomotor performance in terrestrial and aquatic environments. Results: We found significant differences in the locomotor performances among the three species. L. colubrina was the most terrestrial species in habits and sprinted significantly faster than the others during terrestrial locomotion. On the other hand, L. semifasciata was the most aquatic species, and it swam significantly faster than the other two species. These results are consistent with our hypothesis that sea kraits move well in their respective primary environments. With respect to the highly aquatic L. semifasciata, its laterally compressed body form, large body size, and large area of compressed tail are considered to be beneficial to swimming in an aquatic environment. Conclusions: More data are required to understand the superior terrestrial locomotion of L. colubrina, but this species may benefit from its more-cylindrical body form compared to L. semifasciata and from its greater muscle mass compared to L. laticaudata. L. laticaudata was intermediate in habits but exhibited the poorest performance in both swimming and terrestrial locomotion. The reasons for this remain unclear.