For a long time, biologists thought a main function of geckos' tails was to store fat, but a new study gives that couch-potato image a makeover.
In fact, the tail plays an active role in the gecko's amazing ability to climb — for which their sticky feet usually get all the credit — as well as to fall safely.
Ardian Jusufi, his graduate advisor Robert J. Full, and two colleagues, all at the University of California, Berkeley, videotaped flat-tailed house geckos ascending a vertical wall. The team observed that when the lizards' front feet hit a slippery patch and lost their grip, the animals instantly tapped their tails to the wall to keep from pitching backwards. If a tap wasn't enough, they pressed their tails against the wall, like kickstands.
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Tailless individuals had much less success traversing the slick spot than intact animals. (Geckos can jettison their tails when snagged by a predator.)
The researchers also observed gecko tail action in the air: they either dropped the lizards from an upside-down position, or set them afloat in a wind tunnel. By actively rotating their tails, turned-over geckos took just one-tenth of a second to roll right side up — the fastest air-righting response ever reported for an animal without wings. Again, intact geckos outperformed tailless ones.
After self-righting, the geckos calmly glided belly first in a typical skydiving posture, moving their tails to control their direction and angle of descent into a safe landing. Fat storage, my tail!
The research was detailed in the Proceedings of the National Academy of Sciences.
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