Double tails double trouble

February 2010

Are two tails better than one?

When this Robust Velvet Gecko moved into a Brisbane home sporting two tails, the resident human felt sorry for it. 'This gecko can't seem to find a picture to hide behind as they are all taken up by others'. How can lizards grow double tails? Are two tails better than one?

 

Answer

The original tail is supported by a row of vertebrae featuring specialised, weakened breakage points. If grasped, the tail can be severed easily at one of these points. The broken tail wriggles, distracting a predator while the gecko makes a good escape and a "clean break". When a new tail grows from the stump these vertebrae are replaced by a simple cartilage rod.

Robust Velvet Gecko with forked tail Lucky lives up to her name, her tail regrows again!

But what if the original is damaged but not lost? This gecko (let's call her 'Lucky') has sustained a wound and the original tail has not made a clean break; it has healed. Furthermore a new tail has also grown, resulting in a lizard with a forked tail! The new tail (on the right) has quite a different streaked pattern.

And Lucky has had other problems. The original tail, with its blotched pattern continuous with the body markings, has recently had its end bitten off. Lizards can be very territorial so that is likely to have been caused by other geckos guarding their turf. But the second picture taken about 3 weeks later shows that the tip of the original tail is now healing.

When it comes to swiftness, agility and the need to squeeze quickly into those tight cracks, two tails are certainly not better than one!

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