Researchers have made a fascinating discovery about geckos, revealing that they utilize a balance-related mechanism to detect vibrations. This finding offers fresh perspectives on how animals hear and perceive their surroundings.
Biologists from the University of Maryland have uncovered an unexpected sensory ability in geckos, challenging previous assumptions about animal hearing.
A study released in Current Biology on October 4, 2024, highlights that geckos utilize the saccule, a component of their inner ear that is typically linked to balance and body orientation, to sense low-frequency vibrations. The researchers indicate that this unique “sixth sense” not only aids the gecko’s typical hearing but also enhances their ability to perceive their environment. The team proposes that this little-known auditory mechanism could also exist in other reptiles, which may reshape our understanding of how sensory systems in animals have evolved and differentiated over time.
“The ear, in its conventional form, detects airborne sounds. However, this ancient internal channel, usually associated with balance, allows geckos to sense vibrations that travel through solids like ground or water,” noted study co-author Catherine Carr, a Distinguished University Professor of Biology at UMD. “This pathway is present in amphibians and fish, and now we see that lizards retain it as well. Our research illuminates the evolution of the auditory system from its origins in fish to its development in land animals, including humans.”
The saccule is capable of picking up subtle vibrations within the range of 50 to 200 Hz, which is considerably lower than the sounds geckos typically detect with their ears. The researchers suggest that this indicates the saccule has a specific, supplementary role alongside the gecko’s main auditory system. While geckos can hear airborne sounds, many other reptiles lack this capability. Dawei Han, the study’s lead author and a postdoctoral researcher at UMD, believes this discovery regarding the saccule’s function in gecko hearing could enhance our understanding of communication and behaviors in other animals once thought to have limited auditory skills.
“Many snakes and lizards were believed to be ‘mute’ or ‘deaf’ because they don’t produce or respond well to sounds,” Han explained. “However, it appears they may communicate through vibrational signals using this sensory pathway, which significantly alters current perceptions of animal sensory capabilities.”
The presence of this shared sensory pathway in modern reptiles provides valuable insights into the evolutionary development of vertebrate sensory systems, indicating that the shift from aquatic to land habitats likely involved more intricate and gradual adaptations in hearing than previously believed.
While these discoveries do not directly relate to human hearing, the researchers assert that there is often more complexity to uncover—especially concerning our senses.
“Consider being at a loud rock concert,” Carr remarked. “The volume is such that you can feel the vibrations throughout your head and body. You’re experiencing the music beyond merely hearing it, hinting that our vestibular system could be activated in those scenarios, implying a close connection between our senses of hearing and balance.”
Carr and Han aspire for their findings to inspire further research into mammalian hearing, particularly relating to this sensory pathway. They posit that the established link between balance and hearing could unveil new research opportunities, especially regarding human hearing and balance disorders.
“The impacts of this research transcend the realm of reptiles,” Han stated. “As we reveal these hidden functionalities, we build a richer and more intricate understanding of how animals engage with and interpret their environments, potentially offering new insights into our sensory experiences as well.”
This investigation received backing from the National Institutes of Health (Grant No. R01DC019341).
