Gecko can climb walls, but these reptiles are also capable of running across the water as fast as they move on the ground.
How these Geckos manage to avoid sinking into the water is still a mystery until now. The water walking ability has been found in smaller animals such as water striders. This is because of their light weight and so they get to hold up by the surface tension of water which is the force between the surface and water molecules. Whereas bigger animals like the grebe can walk on water, as they powerfully slap the surface with their feet to run. Their fast movement drives down the water under the foot which creates a pocket of air around it.
Geckos are naturally a size that falls among these two categories. Geckos are weak enough to hold themselves up using the surface slap as observed in grebe and they are too heavy and hence cannot leave without breaking the water’s surface.
Early calculations and analysis of videos confirmed that to move faster on the water surface, geckos use a multiple techniques. On analyzing the videos further, it has been found that gecko’s walk was like that of the basilisk. In each step, geckos are retracting the foot through the air and slapping the surface and then stroking under the water. It is observed that a change in water’s surface tension decreases the speed of geckos and the head height was also cut by half when the researchers have added detergent to the water which reduces the overall surface tension.
This shows that geckos are partly using the forces between the water molecules to stay on the surface. Researchers also noticed that geckos definitely use both hydrostatic force and hydrodynamic force which together generates more lift for them. The condition is known as semi-planning.
A profound study could help in creating designs for animal-inspired robots.