Geckos have been observed running across the surface of water in a remarkable feat not seen in any other animals their size.
The lizards use a unique combination of adaptations to stop themselves sinking, including water-repellent skin.
Already known for walking up walls and even gliding through the air, the ability confirms geckos’ reputation as “superheroes” of the reptile world, according to the scientists studying them.
Dr Jasmine Nirody, a biophysicist at the University of Oxford, decided to investigate their abilities after a tip-off about the unusual behaviour from a fellow researcher.
Water-walking had previously been documented in some other animals, notably the basilisk or “Jesus Christ” lizard, which is able to run on its back legs across the surface.
Tiny animals such as spiders are also known to walk on water, relying on its surface tension to keep their tiny bodies from getting wet.
However, the skill had never been observed in more mid-sized creatures that lack both the diminutive size and the strength to prevent them from sinking.
This changed when Dr Ardian Jusufi, a former colleague of Dr Nirody at the University of California, Berkeley, captured footage on his phone of a flat-tailed house gecko in Singapore running across a flooded area.
Dr Nirody and her colleagues were “blown away” by the video, thinking an animal of this gecko’s size should not be capable of propelling itself along the water.
To investigate further, the scientists got hold of some of these geckos, which are native to southern Asia, and proceeded to test their abilities in a tank of water.
Through a series of experiments and high-speed videos, they found the lizards were using an array of techniques to prevent themselves from sinking.
Surface tension proved vital for the small lizards, as adding soap to the tank – which breaks this tension – made it much harder for them to move in the water.
However, they also used the powerful leg-slapping seen in their basilisk lizard cousins to create air pockets that prevented them from becoming submerged.
The geckos were further aided by water-repellent skin and swift strokes of their tails that pushed them along.
“Geckos have this amazing superhydrophobic skin that repels water and enhances their ability to stay above the surface,” said Dr Nirody.
“So in addition to surface tension and slapping, they have their own special trick.”
All of these findings were published in the journal Current Biology.
As moving through air is easier than moving through water, sprinting across the surface is likely an effective strategy for escaping even fast-swimming predators.
“They can run at a metre per second over water. Nothing else can do that; geckos are superheroes,” said Professor Robert Full, a University of California, Berkeley scientist and senior author of the paper.
The scientists suggested that their findings could one day be used to develop robots that can mimic the geckos’ abilities.