Geckos have a hidden ‘sixth sense’ that’s challenging our grasp of animal perception

We all know geckos for their sticky feet and ability to climb walls, but it turns out they have another secret up their scaly sleeves. Scientists have discovered that these little reptiles possess a hidden "sixth sense" that's reshaping our understanding of how animals hear.

Catherine Carr and her team at the University of Maryland found that geckos use a part of their inner ear called the saccule to detect low-frequency vibrations.

Traditionally, the saccule is associated with balance and body positioning, not hearing.

The researchers published their findings in the journal Current Biology .

Their study reveals that this "sixth sense" plays a complementary role to the geckos' normal hearing, offering new insights into how these creatures sense the world around them.

Ancient gecko hearing pathway

"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," said Carr.

"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."

So, what's so special about the saccule? It can pick up faint vibrations ranging from 50 to 200 Hz, well below what geckos usually hear through their ears .

This suggests that the saccule isn't just a backup system but serves a unique function that complements their regular hearing.

Implications for other reptiles

While geckos can hear airborne sounds, many of their reptilian cousins can't. This discovery hints that other reptiles might also use similar mechanisms to perceive their environment .

"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," explained Dawei Han, the study's lead author and a postdoctoral researcher at UMD.

"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 shared sensory pathway in reptiles offers a peek into the evolutionary journey of how vertebrates sense the world.

It suggests that the move from water to land involved more intricate and gradual changes in hearing mechanisms than we previously thought.

Human connection?

Even though these findings aren't directly linked to how humans hear , they remind us that there's often more going on than we realize.

"Think about when you're at a live rock concert. 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," Carr explained.

"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."

What comes next?

Carr and Han hope their work will inspire more studies into how mammals hear, especially regarding this sensory pathway.

They believe that understanding the link between hearing and balance could lead to new research avenues, including exploring connections between human hearing and balance disorders.

"The implications of this research extend beyond the world of reptiles," Han said. "As we uncover these hidden mechanisms, we're also gaining a richer and more nuanced picture of how animals perceive and interact with their environments -- and potentially, new insights into our own sensory experiences."

Gecko hearing and the bigger picture

So next time you see a gecko scurrying up a wall, remember that there's a lot more to these creatures than meets the eye -- or ear.

Who knows what other hidden talents they might have?

This discovery not only changes how we think about geckos but also opens up new questions about the evolution of hearing in all animals.

It shows that sometimes, the answers to big questions can come from the smallest and most unexpected places.

The full study was published in the journal Current Biology .

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