Washington: A new study has provided deeper insight into how geckos alter foot orientation during downhill locomotion.
Found in warm regions of the world, geckos are extremely capable of climbing up steep, smooth surfaces. To do so, they employ an adhesive system, a key evolutionary innovation that facilitates climbing vertically, and even in inverted positions.
On the underside of their toes are "setae," millions of very fine hair-like structures, which provide increased surface area and close contact between the foot and the surface on which it rests.
This adhesive system works best when loading, the application of the gecko's weight, occurs along the long-axis of the toe, and when this loading is along the natural curvature of the setae.
Biologists at the University of California, Riverside, found that when moving on steep downhill surfaces geckos reverse the position of their hind feet to potentially use the adhesive system as a brake and/or stabilizer, resulting in the digits of the hind feet facing backwards and the setae in the hind feet aligned along the natural curvature of the setae to counteract gravity. Specifically, on a 45 degree downhill slope, the geckos were found to rotate their hind limbs up to 70 degrees more posteriorly (toward the tail).
Timothy Higham, an assistant professor of biology, said that this multi-functionality of the gecko adhesive system permits effective locomotion on both uphill and downhill slopes and without this ability, geckos would be effective at going up, but they would not be able to descend as easily.
The research also showed that when geckos move downhill, the forelimbs likely serve as brakes, pressing down on the surface to increase friction; and the hind limbs likely act as stabilizers, akin to the training wheels on a child's bicycle.
The research has applications in robotics, specifically in how robots can be designed to move up and down complicated surfaces.
The study is published in Biology Letters, a publication of the Royal Society.