When danger threatens many lizards can detach their tails, leaving them behind as decoys in the hope that the predator will attack it rather than the lizard itself. But the tail doesn’t just lie there as bait. For half an hour after they’ve been severed, the disembodied tails perform a complex dance, flipping, lunging and jumping up to an inch in the air. These acrobatics serve to distract the predator even further.
For the first time, Timothy Higham and Anthony Russell have studied the movements of severed gecko tails to understand how they can move in such complex ways without any input from the animal’s brain. They anaesthetised four leopard geckos and implanted electrodes into their tails. Once the animals awoke, a small pinch in the right place was enough to prompt them to jettison their tails and scuttle for cover. As the tails started convulsing, Higham and Russell filmed them with high-speed cameras.
Their tips rapidly swung back and forth but between these rhythmic flexes, they behaved more erratically. They flipped by pushing the tip against the floor to launch the whole organ into the air and they lunged by doing the same, but horizontally.
These conspicuous movements increase the odds that an attacking predator will go for the tail instead of the lizard. But it’s actually in the lizard’s interests for both its body and its tail to escape being eaten – geckos and other lizards store valuable reserves of fat in their tails, and these are too valuable to leave to the jaws of another animal. As such, Higham and Russell think that the arrhythmic jumps and flips make the tail more unpredictable and harder to catch. They also increase the odds that the tail will flip to safety, say in a nook or crevice. The lizard can then return later to chow down on its ex-body part.