Snakes can hear and react to sound traveling through the air, which means they can hear stomping around before you arrive, and the screams when you see them! You scaredy-cat.
The new research which reveals this somewhat distressing news was done in Queensland with real snakes which were not anaesthetised.
“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,” says Dr Christina Zdenek, a postdoctoral research fellow in the School of Biological Sciences at the University of Queensland, Australia.
“But our research – the first of its kind using non-anesthetised, freely moving snakes – found they do react to soundwaves, and possibly human voices,” says Zdenek, who is the first author of the paper.
Despite the absence of an ear drum and external ears, snakes aren’t deaf. (But now I’m imagining snakes with human ears on their heads… cute!)
Like us they have an inner ear and can sense sound waves that cause their head to vibrate. Bones, called the quadrate and columella – think it’s evolutionary homologue the stapes ear bone in mammals – attached to the jaw bone, are stimulated by vibration and relay the signal.
This study involved 19 captive-bred Australian adult snakes representing five distinct genera: death adders (Acanthophis), woma pythons (Aspidites), pale-headed snakes (Hoplocephalus), Taipans (Oxyuranus), and brown snakes (Pseudonaja). These species range from active foragers to ambush predators, arboreal species, and constrictor feeders.
“We played one sound which produced ground vibrations, while the other two were airborne only,” explains Zdenek.
“It meant we were able to test both types of ‘hearing’ – tactile hearing through the snakes’ belly scales and airborne through their internal ear.’
Zdenek told Cosmos that they tested frequency ranges of 0–450 Hertz, which includes the frequency of the human voice (about 100–250Hz depending on the sex).
“Plus, the loudness we used (85 decibels, at a distance of 1.2 metres away from the snake), is the amplitude of a loud voice.
“Normal conversation is about 60db, which is quieter than what we tested. Not to say they can’t hear and interpret that loudness – we just didn’t test sound at that loudness.”
So yes, it’s fair to say that snakes can hear it when you shriek like a child at the sight of them.
The team quantified eight different snake behaviours in reaction to the sounds including: body movement, body freezing, head-flicks, tongue-flicks, hissing, periscoping (lifting head and neck), head fixation, and lower jaw drop.
They found that how the individuals reacted to sounds strongly depended on the genus of the snake.
“The woma python tended to move toward sound, while taipans, brown snakes and especially death adders were all more likely to move away from it,” says Zdenek.
“The types of behavioural reactions also differed, with taipans in particular more likely to exhibit defensive and cautious responses to sound.
These differing reactions are likely because of distinct evolutionary pressures and probably aid in 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,” Zdenek adds.
“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.”
These findings add to scientists’ limited understanding of hearing and behaviour in snakes and challenges the assumption that snakes can’t hear sound.
“We know very little about how most snake species navigate situations and landscapes around the world,” Zdenek concludes.
“But our study shows that sound may be an important part of their sensory repertoire.
“Snakes are very vulnerable, timid creatures that hide most of the time, and we still have so much to learn about them.”
The research is in the journal PLOS ONE.