A study by the University of Queensland discovered that snakes can hear and respond to airborne sounds in addition to ground vibrations.
Dr. Christina Zdenek from UQ's School of Biological Sciences, in collaboration with QUT's Professor Damian Candusso, played three different sound frequencies to captive-bred snakes one at a time in a soundproof room and observed their reactions.
"Because snakes don't have external ears, people typically think they're deaf and can only feel vibrations through the ground and into their bodies," Dr. Zdenek said.
"But our research - the first of its kind using non-anesthetized, freely moving snakes - found they do react to soundwaves traveling through the air, and possibly human voices," she said.
The study involved 19 snakes, representing five genetic families of reptiles.
"We played one sound which produced ground vibrations, while the other two were airborne only," Dr. Zdenek said.
"It meant we were able to test both types of 'hearing' - tactile hearing through the snakes' belly scales and airborne through their internal ear," she added.
The reactions strongly depended on the genus of the snakes.
"Only the woma python tended to move toward the sound, while taipans, brown snakes, and especially death adders were all more likely to move away from it," Dr. Zdenek said.
"The types of behavioral reactions also differed, with taipans, in particular, more likely to exhibit defensive and cautious responses to sound.
Dr. Zdenek said the different reactions are likely because of evolutionary pressures over millions of years, designed to aid survival and reproduction.
"For example, woma pythons are large nocturnal snakes with fewer predators than smaller species and probably don't need to be as cautious, so they tended to approach sound," Dr. Zdenek said.
"But taipans may have to worry about raptor predators and they also actively pursue their prey, so their senses seem to be much more sensitive."
Dr. Zdenek said the findings challenge the assumption that snakes can't hear a sound, such as humans talking or yelling, and could reshape the view of how they react to sound.
"We know very little about how most snake species navigate situations and landscapes around the world," Dr. Zdenek said.
"But our study shows that sound may be an important part of their sensory repertoire," she added, saying, "Snakes are very vulnerable, timid creatures that hide most of the time, and we still have so much to learn about them."
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