Naturalists once believed reptiles like lizards and snakes relied primarily on sight and smell, with inner ears mainly for balance. However, new research reveals a surprising ability: a gecko's balance organ also detects ground vibrations.
This discovery, focusing on the tokay gecko, rewrites part of the evolutionary story of hearing. It suggests an ancient vibration pathway, previously overlooked, never vanished when vertebrates moved onto land.
Researchers recorded nerve signals in the saccule, a fluid-filled pouch in the gecko's skull, while delivering low-frequency shakes. The saccule responded, indicating a second sound channel for tremors, separate from the eardrum.
"The ear, as we know it, hears airborne sound. But this ancient inner pathway, which is typically linked to balance, helps geckos detect vibrations that travel through media such as ground or water," explained study co-author Catherine Carr, a Distinguished University Professor of Biology at the University of Maryland.
The study, published in Current Biology, also found a dedicated vibration highway in the gecko brain, the nucleus vestibularis ovalis. Similar structures in snakes and the Sphenodon suggest a shared sensory blueprint across reptiles.
This research highlights that many snakes and lizards may communicate through vibrational signals. This changes how scientists think about animal perception. Other animals, like desert sand-diving snakes and turtle hatchlings, may also use this sensory pathway.
The gecko's vibration sense may have been carried ashore by early tetrapods. The study's findings could influence therapies for balance disorders and inspire new designs for earthquake sensors.
By understanding how geckos sense vibrations, scientists are uncovering a sensory mosaic that stretches back hundreds of millions of years.