Researchers at the University of Maryland have uncovered a hidden and unexpected auditory “sixth sense” in geckos.
In a study published in Current Biology, scientists revealed that geckos use a specialized part of their inner ear, known as the saccule, to detect low-frequency vibrations—a trait previously unrecognized in reptiles.
Researchers believe other species could have a similar sixth sense. This would offer new insights into how animals perceive their environment and could have significant implications for evolutionary biology.
“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 mediums like the ground or water,” study co-author and Professor of Biology at UMD, Dr. Catherine Carr, said in a press release. “This pathway exists in amphibians and fish, and now it’s proven to be preserved in lizards as well. Our findings shed light on how the auditory system evolved from what you see in fish to what you see in land animals, including humans.”
Typically associated with balance, the saccule is a part of the inner ear that allows geckos to sense vibrations through mediums like the ground or water rather than through airborne sounds like traditional hearing.
The saccule’s sensitivity to vibrations between 50 and 200 Hz complements the gecko’s regular auditory system. This finding is significant when considering other reptiles, such as snakes or different species of lizards.
Traditionally, many reptiles are believed to be “deaf” or “mute” because they do not vocalize sounds or respond well to airborne noise. However, the ability to detect vibrations offers a new explanation. Reptiles may communicate through vibrational signals, challenging long-held assumptions about their sensory perception.
“A lot of snakes and lizards were thought to be ‘mute’ or ‘deaf’ in the sense that they do not vocalize sounds or hear sounds well,” lead study author and PhD candidate Dawei Han explained. “But it turns out they could potentially be communicating via vibrational signals using this sensory pathway instead, which really changes the way scientists have thought about animal perception overall.”
This “sixth sense” in geckos also offers fresh insights into the evolution of hearing mechanisms across species. The saccule, present in both amphibians and fish, now shows its role in reptiles, suggesting that auditory systems may have developed more gradually and with greater complexity than previously believed. These findings highlight how hearing mechanisms likely adapted during the shift from aquatic to terrestrial environments, revealing a more nuanced evolutionary pathway than was once assumed.
The surprising discovery of an auditory “sixth sense” in geckos also raises intriguing questions about the potential for unexplored sensory abilities in humans. It opens the door to new research into the human auditory system, prompting scientists to consider whether we have similar undiscovered pathways that contribute to our perception of the world.
“Think about when you’re at a live rock concert,” Dr. Carr said. “It’s so loud that you can feel your whole head and body vibrate in the sound field. You can feel the music rather than just hearing it.”
“That feeling suggests that the human vestibular system may be stimulated during those loud concerts, meaning our sense of hearing and balance may also be linked closely.”
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