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

Abstract

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 Laticauda 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.

Peaceful coexistence between people and deadly wildlife: Why are recreational users of the ocean so rarely bitten by sea snakes?

“…move between the ocean and the land mostly from dusk to dawn (e.g. Shetty & Shine, 2002; Shine, et al., 2003; Shine, et al., 2003) but forage actively at sea at all hours of the day and night (Cook et al., 2016). Information on the other species is more fragmentary but Burns and Heatwole (1998) reported that radio‐tracked Aipysurus laevis foraged both by day and by night.…”

Why implantation of bio‐loggers may improve our understanding of how animals cope within their natural environment

“…For instance, Lutterschmidt et al (2006) implanted loggers into the general body cavity of free-ranging red-sided garter snakes (Thamnophis sirtalis parietalis) and recorded body temperatures during their winter dormancy. More recently, Cook et al (2016) used intraperitoneal implantation of a time-depth recorder and a radio-transmitter in sympatric sea kraits to investigate their at-sea foraging behavior and energy budgets.…”

The behaviour of sea snakes (Emydocephalus annulatus) shifts with the tides

“…Logistical impediments to observing snakes underwater are responsible for that lack of information. Recent developments in telemetry are providing far more detailed datasets on activity patterns and habitat use of marine snakes [15][16][17][18][19][20] but without direct information on behaviour. One striking exception involves studies showing that rising tides induce sea snakes (Hydrophis elegans and H. major) to shift habitat use (from open sites into seagrass beds) to avoid predation risk from sharks as water levels rise 21,22 .…”