How does a gecko’s tail regenerate?

(Felipe Sasso/Flickr)

First, it’s important to know that lizards and geckos shed their tails of their own accord. This is not a masochistic crisis of self-flagellation, but a very clever strategy that helps the animal to save its life. When chased, it cuts off a piece of its own tail, which keeps moving for a while, enough to distract the predator and it can run away. “It’s better to lose your tail than your life”, says biologist Fábio Molina, head of the Reptiles Sector at the Zoological Park Foundation, in São Paulo, SP. This autotomy (spontaneous mutilation) happens thanks to the contraction of the muscles of the tail at fracture points, where the joints between the vertebrae are looser. In these places, all tissues – vessels, muscles, nerves, etc. – are more easily disconnected. Afterwards, the tail will be regenerated, however, it will never be the same. The new tail will be smaller, thicker or crooked.

The bone part also does not recover. “In the part of the tail that regenerates, the vertebrae are replaced by a cartilage rod with no planes of fracture. This means that new autotomy can only occur at points prior to the beginning of the regenerated tail”, says Fábio. The regeneration time depends on the metabolism of the animal and even the season of the year – in the summer, the new tail is born faster – but, on average, it takes three weeks. The energy spent for the regeneration of the tail has a high price: young individuals grow longer and females in the reproductive phase produce fewer eggs.