New research demonstrates that snakes use hearing to assess their environment, dispelling the myth that they are deaf to airborne sounds.
Experts have known for a long time that snakes can feel sound vibrations via the ground – a phenomenon known as “tactile” sensing – but it’s been unclear if they can also hear airborne sound waves and how they react to noises.
In a report published today in PLOS ONE, we conclude that snakes use hearing to perceive their environment, eliminating convincingly the misconception that snakes are deaf to airborne sounds.
Our research, which involved seven species and 19 individual snakes, demonstrates that not only do snakes have airborne hearing, but also that various species react differently to what they hear.
Despite the fact that seeing and tasting (the air) are the primary ways snakes perceive their environment, our research demonstrates that hearing remains an important part of their sensory repertoire.
This is rational from an evolutionary standpoint. Predators that prey on snakes include monitor lizards, cats, dogs, and other snakes. Auditory perception is essential for predator avoidance and harm prevention (such as being trodden on).
For our research, we teamed with the School of Creative Practice at the Queensland University of Technology to soundproof a room and test a single snake.
Using quiet as a control, we played one of three noises, each with a distinct frequency range: 1–150Hz, 150–300Hz, and 300–450Hz. Comparatively, the human voice range is approximately 100–250 Hz, but birds chirp at approximately 8,000 Hz.
In a prior investigation, researchers hung western diamondback rattlesnakes (Crotalus atrox) in a steel mesh basket and observed their restricted responses to sound frequencies between 200Hz and 400Hz. Other researchers placed electrodes surgically into the brains of partially anesthetized snakes, recording electrical potentials in response to sounds up to 600 Hz.
But our research is the first to examine how multiple snake species react to sounds in a free-moving environment. In addition, we utilized an accelerometer to determine if the sounds caused ground vibrations. This allowed us to confirm that the snakes were truly detecting airborne noises and not simply ground vibrations.
In comparison to the control, the majority of snakes demonstrated vastly different types of behaviors during sound trials.
Woma pythons (Aspidites ramsayi), a non-venomous snake found in the arid interior of Australia, increased their movement in reaction to sound and approached it. They displayed an intriguing behavior known as “periscoping,” in which snakes elevate the front third of their bodies in a manner indicating curiosity.
In contrast, three other genera—Acanthophis (death adders), Oxyuranus (taipans), and Pseudonaja (brown snakes)—were more likely to move away from sounds, indicating possible avoidance behavior.
Death adders are predatory ambush hunters. They rely on the lure on their tail (which they wriggle to resemble a worm) to attract prey, and they cannot move swiftly. Therefore, it seems sense that they departed from the sound. They must avoid being trampled by large vertebrates such as kangaroos, wombats, and people in order to survive.
Brown snakes and taipans are energetic daytime predators that pursue their prey with great speed. This makes them susceptible to daylight predators like raptors. During our studies, both of these snakes exhibited keen senses. Particularly taipans were likely to exhibit defensive and wary behaviors in reaction to sound.
Our research disproves the idea that snakes are deaf. They are able to hear, just not as well as you or I. Comparatively, snakes can only hear frequencies below 600 Hz, but most of us can hear a considerably broader range. Perhaps snakes perceive garbled versions of what we hear.
Then, can reptiles hear us? Depending on sex, the frequency of the human voice ranges between 100 and 250 Hz. These frequencies were included in the sounds produced throughout our trials, which were conducted at a distance of 1.2 meters and 85 decibels from the snakes. This represents the volume of a loud voice.
Many of the snakes in our study responded considerably to this sound. Therefore, it is probable that snakes can hear loud voices and screams. That does not imply that they cannot hear someone speaking (a normal conversation is roughly 60 dB) – we just did not test sound at that level of noise.
»Science disproves myth that Snakes are deaf«