Many species of lizards have mastered the art of escape.
Fractures on their vertebrae allow them to detach along multiple points of their tails.
With cracks in their bones, one would expect them to lose their tails often.
Yet unless they’re in danger, most species’ tails stay faithfully attached. And when their tails
do detach, some lizards can grow them back. After all, the tail is an important organ,
helping them move and balance with ease. Inspired by the lizards crawling around their
desert campus, researchers at NYU Abu Dhabi set out to understand how lizard tails achieve the
Goldilocks principle: a tail that isn’t attached too firmly or weakly but stays on “just right.”
Using a scanning electron microscope, the scientists took a closer look at the “plug
and socket” of muscles surrounding fractures on the lizards’ vertebrae.
A previous study discovered that these plugs were made up of smaller pillars.
This time the researchers imaged the interior of the sockets. They expected them to contain
grooves that the micropillars inserted into, to create a strong, interlocking bond.
Instead, they found that the sockets were mostly smooth, speckled with faint imprints
of the micropillars’ tops. This meant the muscle plugs were merely touching the sockets’ surface.
They also found many small holes on the top of these pillars—and
suspected that these nanopores were key to keeping the tail attached.
To test this, they used silicone patches and glass to make a lizard tail model.
They created two types of patches with and without nanopores: one set contained short micropillars,
while the other had taller micropillars, similar to what is seen in lizards.
The scientists pulled the patches apart from the glass and found that longer pillars with
nanopores were the hardest to pry apart. In real life, body fluids fill the nanopores
and micropillars in a lizard’s tail. To mimic this, the researchers added water to the silicone
patches. They found that this made the silicone patches adhere more strongly to the glass.
Models revealed that small cracks between the micropillars and socket,
caused by the nanopores, slowed down new cracks that developed in the tail.
With all these strong connections, how do lizards drop their tails?
The researchers captured three different species of lizards and used a high-speed camera to film
the moment their tails detached from their bodies. When they pulled at the tail or squeezed it,
the lizard tail stayed firmly attached. But when grasped by the far end of their tail,
the lizard was able bend their tail. This triggered a fracture that allowed them to
peel their tails off their bodies and run away. While two species they tested had an easy escape,
one species had to twist and turn in order to release from its predator’s grasp.
Using their lizard tail model, the scientists found that
peeling patches off the glass was far easier than pulling them off.
They also used a virtual model to understand how a lizard’s muscles might help them
detach their tails. They found that if less stress was applied to the silicone patches,
a scenario similar to a lizard contracting its muscles, it was easier to peel off the patches.
They hope the mechanisms behind this balancing act can inspire new products,
such as bandages in the mouth, where chemical adhesives wouldn’t work as well.
Sometimes it takes a gross encounter to inspire the most creative solution to our problems.