The Mystery of the Lizard Tail Explained

Researchers present the first-ever biophysical model of lizard tail autotomy

In a new study published in the journal Science, a team of researchers led by NYUAD Associate Professor of Mechanical Engineering and Bioengineering Yong-Ak (Rafael) Song, presents the first-ever rigorous biophysical model of lizard tail autotomy.

It’s well known that lizards have the ability to escape predators by losing -- and later regenerating -- their tails, but researchers have continued to try to understand the underlying mechanism of the tail autotomy process. Song and his team have determined the mechanism of the highly dense mushroom-shaped micropillars covered with nanopores which play a pivotal role in tail autotomy.

In the paper Biomimetic fracture model of lizard tail autotomy, Song and colleagues captured SEM micrographs of both the tail and body of lizards after shedding. The researchers observed that the mushroom-shaped micropillars covered with  nanopores on the top established surface-to-surface  connections along the tail fracture planes that are exposed to higher vulnerability in bending mode (as the tail prepares to break off) than in tensile mode.

While allowing easier shedding than regular form-based interlocking, the micropillars also displayed intrinsic toughening mechanisms to aid the tail  remain firmly attached to the body as long as possible when desired in non life-threatening situations. The team also captured the tail breakage process using a high-speed camera, and found that the bending of the tail plays a crucial role in initializing the autotomy process by initiating a crack on the bent side. The computer model showed that if lizards contract their muscles around the tail-body connections to further reduce the pre-stress of the attachment, this muscle contraction can also ease up the shedding process along with the bending motion.

The science behind the nearly miraculous process of tail autotomy has puzzled scientists for years.  This study has provided insights into one of the most fascinating adhesion-based systems found in nature, and has far-reaching implications in adhesion-related-applications. These include skin grafts, wound healing, soft robotics, flexible hybrid electronics, bio- and pressure-sensitive adhesives, and transfer- and 3D bioprinting.

“Using the multiscale strategy our team has uncovered, the lizard carefully balances attachment and detachment, achieving the ‘just right’ connection in its tail that is neither too weak nor too strong for its best chance of survival. It is our hope that our work can guide the future research of these mysterious reptiles and unlock the potential for applications in medicine and beyond.”

NYUAD Associate Professor of Mechanical Engineering and Bioengineering Yong-Ak (Rafael) Song