Foraging behaviour and energy budgets of sea snakes: insights from implanted data-loggers.

International audience

English. Information on the foraging behaviour of sea snakes has the potential to clarifyadaptive pathways involved in the evolutionary invasion of marine habitats byterrestrial vertebrates. However, logistical obstacles have precluded studies in thisfield. To obtain preliminary data of diving behaviour, we surgically implantedtemperature-depth loggers into two sympatric, amphibious, benthic foraging seakrait species from New Caledonia. Based on logger recovery from three snakes (1Laticauda laticaudata and 2 L. saintgironsi), we obtained data on a total of 1850dives carried out over eight foraging trips and 39.6 days at sea. Almost 99% ofdives were <30 m deep. Average dive depth was 10.7 ± 7.0 m, but snakes dived asdeep as 82.6 m. Maximum dive duration was ≥123.7 min. At sea, snakes divedcontinuously, with over 90% of surface recovery periods lasting less than 3 min inL. saintgironsi (n = 1). Periods at the surface (between successive dives) werelonger at night than by day, plausibly reflecting more intense hunting activity bythe snake. Locomotor speed, as measured by the rate of vertical descent or ascentduring diving, was low (0.15 m s−1). In combination with other data on thesespecies, we estimate that metabolic expenditure was about 10 times greater whilethe 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 fordiving endotherms. Despite low sample sizes, our study shows that implanted dataloggers can provide novel insights into sea snake biology. Our data emphasize thebehavioural and ecological consequences of ectothermy for secondary marinevertebrates. In particular, they illustrate how ectothermy allows species to thriveon rates of energy intake vastly lower than are required for their endothermiccompetitors.