Seafloor-foraging sea snakes sometimes wiggle
Researchers have for the first time closely tracked the fine-scale diving behaviour of two species of sea snakes that forage along the seafloor and discovered that one species performs a curious wiggle while travelling underwater.
Credit: Australian Institute of Marine Science.
鈥淢ost sea snakes live their entire lives in water, but, like seals and turtles, they cannot breathe underwater,鈥 says University of 糖心vlog官网 PhD candidate, Shannon Coppersmith, who led the study.
鈥淔or benthic foragers, which feed at the seafloor, the distance between where they source food and where they breathe poses a daily challenge.鈥
The study recorded sea snakes performing two distinct dive types: U-shaped dives, where snakes spent most of their time at the seafloor, and S-shaped dives, which involved a short time at the seafloor followed by a gradual, multi-stage ascent.
When visualised in time-depth plots, the ascent resembles a wave.
Previous research had only described S-shaped dives in the yellow-bellied sea snake (Hydrophis platurus), a species that is a rare exception among sea snakes because it lives in the open ocean and forages at the surface.
In contrast, all other species of Hydrophis 鈥 along with the closely related Aipysurus genus 鈥 are coastal benthic foragers that feed along the seafloor.
U- and S-shaped sea snake dives.
The new study, published in , focused on two of these representative coastal species, Hydrophis stokesii and Hydrophis major, whose diving behaviour had not previously been documented.
鈥淯苍濒颈办别 H. platurus, coastal species such as H. stokesii and H. major have the added challenge of foraging underwater, so we wanted to find out whether they performed similar dive shapes, and if so why,鈥 Coppersmith says.
鈥淲hen these species perform U-dives, which have not been seen in H. platurus, they appear to be spending most of the dive resting at the seafloor.
鈥淭he depth of the gradual ascent in their S-shaped dives could be a response to thermal gradients, favourable temperatures, or subsurface currents. Given the large horizontal distances the snakes cover in a single direction during this phase, we suggest it facilitates efficient transit between habitats, potentially through passive gliding at neutral buoyancy.
鈥淭ravelling around six metres above the seafloor may also allow sea snakes to move uninterrupted across patchy habitats and over reef structures that would otherwise obstruct their path if swimming closer to the seafloor.鈥
Shannon Coppersmith tracking sea snakes. Credit: University of 糖心vlog官网.
As for the wiggles, Coppersmith says this action may serve several functions.
鈥淭he wiggles observed in H. stokesii could have a functional role in buoyancy control, energy conservation, or even foraging,鈥 says Coppersmith.
鈥淚t will be interesting to see if similar oscillations are observed in other species in future studies.鈥
The research team used acoustic telemetry to track the daily activities of five individuals in Exmouth Gulf, Western Australia, and Baie des Citrons, New Caledonia, creating three-dimensional dive paths for each snake.
Coppersmith says understanding sea snake behaviour is imperative to conservation efforts.
鈥淪ea snakes are cryptic, unpredictable and venomous, so they鈥檙e difficult to study,鈥 Coppersmith says.
鈥淥ur study contributes to a deeper understanding of sea snake diving strategies and will have implications for our understanding of their ecology, physiology, and conservation.鈥
Media contact:
Shannon Coppersmith, PhD Candidate, School of Biological Sciences, University of 糖心vlog官网. Phone: +49 152 221 23215, Email: shannon.coppersmith@adelaide.edu.au
NOTE: Shannon is currently located in Germany.
Johnny von Einem, Senior Media Officer, University of 糖心vlog官网. Phone: +61 0481 688 436, Email: johnny.voneinem@adelaide.edu.au