Sunday, 23 April 2017

Gecko Feet - how do they stick?

In "Whose Feet are These?" I wrote about geckos having 'sticky' feet, which seemed a good way to describe gecko feet for young children. But how exactly are geckos' feet sticky? Here's a photo of the foot of a common or raukawa gecko, doesn't it look amazing!

Raukawa Gecko foot - each gecko species has
a different footprint

Geckos have lots of tiny hairs on their feet, too small to see in this photo. These tiny hairs branch into even tinier hairs - "nano-hairs". Because the gecko has so many tiny hairs on its foot, the foot has many many points of contact with the surface that it's on. These hairs can get in so close to the surface that an attraction is created between the molecules of the surface and the hairs, which is what holds the gecko on. Although walls, glass and ceilings look smooth to us, under a microscope they'd look quite rough. So perhaps you could think of a gecko's hairs and the wall sticking together a bit like microscopic velcro.
Early one morning I found a gecko on the outside of the
kitchen window
Of course geckos need to be able to let go too, otherwise they'd be stuck for ever. The tiny hairs are on a slanted angle (not at 90 degrees) and this angling helps them stick and unstick.
A gold-striped gecko climbs a smooth flax leaf
Straight up the leaf 
To the very top!
Experts talk about gecko feet:
Here's David Attenborough talking about sticky gecko feet with some amazing close ups of the hairs.
And some articles for adults about how gecko feet work on Live Science and another with a diagram of the hairs in the LA Times.

For more of my stories about geckos see:
Geckos and Skinks -what's the difference?
Geckos in the Spotlight - volunteering on Mana Island
Make a Gecko with Sticky Feet  - children's activity

For activities and ideas about animals' feet see:
Whose Feet are These? Notes for children, parents and educators