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Information on the foraging behaviour of sea snakes has the potential to clarify adaptive pathways involved in the evolutionary invasion of marine habitats by terrestrial vertebrates. However, logistical obstacles have precluded studies in this field. To obtain preliminary data of diving behaviour, we surgically implanted temperature-depth loggers into two sympatric, amphibious, benthic foraging sea krait species from New Caledonia. Based on logger recovery from three snakes (1 L aticauda laticaudata and 2 L . saintgironsi), we obtained data on a total of 1850 dives carried out over eight foraging trips and 39.6 days at sea. Almost 99% of dives were <30 m deep. Average dive depth was 10.7 ± 7.0 m, but snakes dived as deep as 82.6 m. Maximum dive duration was ≥123.7 min. At sea, snakes dived continuously, with over 90% of surface recovery periods lasting less than 3 min in L. saintgironsi ( n = 1). Periods at the surface (between successive dives) were longer at night than by day, plausibly reflecting more intense hunting activity by the snake. Locomotor speed, as measured by the rate of vertical descent or ascent during diving, was low (0.15 m s−1). In combination with other data on these species, we estimate that metabolic expenditure was about 10 times greater while the snakes were at sea than on land; and their overall field metabolic rate (70-145 kJ kg−1 day−1) was an order of magnitude less than has been reported for diving endotherms. Despite low sample sizes, our study shows that implanted data loggers can provide novel insights into sea snake biology. Our data emphasize the behavioural and ecological consequences of ectothermy for secondary marine vertebrates. In particular, they illustrate how ectothermy allows species to thrive on rates of energy intake vastly lower than are required for their endothermic competitors. [ABSTRACT FROM AUTHOR]

Body mass positively influences diving capacities in air-breathing vertebrates and has been identified as a key determinant for the evolution of diving. Our review on the relationship between body mass and dive duration (a major parameter of dive performances) encompassed for the first time a wide diversity of air-breathing vertebrates. We included a substantial number of nonavian and nonmammalian diving species belonging to various independent lineages (sea snakes, iguana, turtles and crocodiles). Our analyses suggest that the widely accepted size dependency of dive duration applies with significantly less force in ectotherms compared with endotherms; notably we failed to detect any effect of body mass in ectotherms. We hypothesize that the absence of tight physiological links between body mass and respiratory demands documented in ectotherms blurred our ability to detect the expected correlation. Further exploration of the evolution of diving physiology may well necessitate adopting novel perspectives to encompass both ectothermic and endothermic modes. [ABSTRACT FROM AUTHOR]