Geckos are famed for their extraordinary ability to scale walls, run across ceilings and even hang upside down from apparently smooth materials like glass.
Microscopic hairs allow the lizards to employ dry adhesion – meaning they can stick to surfaces without the use of liquids or surface tension – through the creation of so-called van der Waals forces which draw materials together.
Their amazing climbing skills have long been a source of fascination for scientists, and have even led to the invention of adhesive tape that mimics the properties of their specialised toe pads to easily attach and detach.
But some elements of their abilitihat their adhesive ability was related to the size of their toe pads, allowing les have remained a mystery, including how some of the heavier species (weighing up to 250g) can still stick to things so effectively. The assumption was targer geckos to climb just as well as the smaller ones (which weigh as little as 2g).
But now a team of scientists at the University of Massachusetts Amherst, US, have shown that additional factors are also at play. They've discovered that their bodies become stiffer as they grow bigger, acting like a spring, giving their adhesion the increased power needed to support more weight.
“This is an exciting result because it shows how simple mechanical changes in the adhesive system explains how large geckos can climb effectively," explains Professor Duncan J. Irschick, co-author of the study.
They based their hypothesis on recent work which showed that man-made adhesives inspired by gecko's adaptations get stronger as they are made stiffer, or less compliant.
"Prior theory has shown that synthetic adhesive systems become more powerful if they are stiffer, and we wanted to see if this theory was upheld in living animals," Prof Irschick says.
