Things that go CHURP in the night!

Bedtime in Bali can be intense. During the day there are animals that sing or croak or buzz in plain sight. I’m fine with that. But when darkness descends everything ramps up a notch. There is a creature that makes a seriously frightful sound and it waits until a moment after I turn out my light to terrify me with its raspy, croaking call. If the noise was coming from the rice fields, or the trees outside I could handle it. But it sounds like it’s perched on my headboard. Imagine a duck, but instead of quack quack it says WHACK-O, WHACK-O. Every time this happens I turn on the light with heart-stopping speed but there is nothing there. Nothing. Just WHACK-O, WHACK-O, six or eight times then its over.

Okay, so that’s one unnerving detail. Then there’s the chirping that isn’t a bird-like chirp, it’s more of a, well, its louder and bigger than a bird chirp. That starts after dark as well. I was sitting at my computer and all of a sudden this big voice “CHURP!” made me jump. I whipped around and here was a sweet little gecko staring at me with his unblinking eyes. I stared back and said, “That couldn’t have been you.” He neither agreed nor disagreed, he just kept staring. So I shrugged, turned back to my work and “CHURP!”

That is what prompted my hasty gecko research. What fascinating creatures! And yes, it was him. Not only that, he has about 200 relatives that live very close by and they all like to make themselves heard. But back to the research. Their voices are an interesting feature but their feet are utterly fascinating.

Here, taken from Wikipedia, is the story of the gecko’s sticky feet.

Adhesion ability

The toes of the gecko have a special adaptation that allows them to adhere to most surfaces without the use of liquids or surface tension. The spatulae tipped setae (hairs) on gecko footpads facilitate attractive forces called van der Waals forces (the sum of attractive or repulsive forces between molecules) to arise between the structures and the surface.

These van der Waals interactions involve no fluids; in theory, a boot made of synthetic setae would adhere as easily to the surface of the International Space Station as it would to a living room wall, although adhesion varies with humidity. The setae on the feet of geckos are also self-cleaning and will usually remove any clogging dirt within a few steps.

Geckos’ toes seem to be “double jointed“, but this is a misnomer. Their toes actually bend in the opposite direction from human fingers and toes. This allows them to overcome the van der Waals force by peeling their toes off surfaces from the tips inward. In essence, this peeling action alters the angle of incidence between millions of individual setae and the surface, reducing the Van der Waals force. Geckos’ toes operate well below their full attractive capabilities for most of the time. This is because there is a great margin for error depending upon the roughness of the surface, and therefore the number of setae in contact with that surface.

Use of small van der Waals attraction force requires very large surface areas: every square millimeter of a gecko’s footpad contains about 14,000 hair-like setae. Each seta has a diameter of 5 micrometers. Human hair varies from 18 to 180 micrometers, so a human hair could hold between 3 and 36 setae. Each seta is in turn tipped with between 100 and 1,000 spatulae. Each spatula is one five-millionth of a meter long, or just below the wavelength of visible light.

If a typical mature 2.5 oz gecko had every one of its setae in contact with a surface, it would be capable of holding aloft a weight of 290 lbs. Recent studies have also revealed that apart from the setae, phospholipids – fatty substances produced naturally in their body – also come into play. These lipids lubricate the setae and allow the gecko to detach its foot before the next step.

Congratulations! If you made it through these paragraphs and understood what you were reading you just passed Biology 101! Seriously though, what amazing technology.

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1 Comment (+add yours?)

  1. Diane Struble
    Apr 21, 2012 @ 17:17:19

    Thanks for the biology lesson. As long as they are geckos and not snakes, I’m good.

    Like

    Reply

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