Microscopic hair makes gecko feet sticky, study says

The microscopic hair, called setae, present underneath the toes of a type of gecko make the reptile's feet sticky even on smooth surfaces such as leaves and slippery stems, a new study has found.

The findings indicate that the origin of adhesion in geckos was gradual and led to major shifts in ecology and function.

A team led by gecko expert Timothy Higham from the University of California, Riverside in the US studied Gonatodes - a genus of dwarf geckos - and found that a gecko, Gonatodes humeralis, in South America, offers a "snapshot" into the evolution of adhesion in geckos.

"Our integrative analysis of this gecko shows that unexpectedly it has microscopic hairs, called setae, underneath its toes, which allow it to do something dramatically different than all other geckos in the Gonatodes genus: cling to smooth surfaces such as leaves," Higham said.

"It does this without all of the complex structure of the toes that typify the geckos that we are more familiar with. In the lab, this gecko can climb smooth vertical surfaces using its incipient adhesive system," he added.

Researchers explained that the setae interact with surfaces through attractive van der Waals forces.

The relatively simple expression of setae on the digits of G humeralis humeralis thus provide an enormous advantage in sectors of the habitat typified by smooth, low-friction, inclined surfaces, such as leaves and slippery stems, allowing it to avoid predators by occupying habitat that other members of the genus cannot, researchers said.

While it can securely attach to vertical bamboo shoots, for example, other species in the Gonatodes genus generally scale rough tree trunks, rocks, fallen palm trees and move on the ground - areas where their predators abound.

"The relatively simple adhesive system of the G humeralis is indicative that slight modifications in form can dramatically influence functional outcomes and the ecological niches that can be exploited," Higham said.

"This ostensibly padless gecko offers us a snapshot - a crucial intermediate stage - of the evolution of the adhesion apparatus. It is telling us, 'Look, this is how pad-bearing geckos started to acquire adhesion,'" he said.

Researchers suggest that subtle morphological changes are able to trigger rapid evolution.

The study was published in the Biological Journal of the Linnean Society.