Evidence suggests that snakes can hear, but how they naturally respond to sound is still unclear. Scientists from the University of Queensland, Australian Reptile Academy, and the Queensland University of Technology conducted a series of controlled experiment trials on 19 snakes across five genera in a sound-proof room, observing the effects of three sounds on individual snake behavior, compared to controls. They quantified eight snake behaviors — body movement, body freezing, head-flicks, tongue-flicks, hissing, periscoping, head fixation, lower jaw drop — in response to the sounds.
A woma python in the wild. Image credit: Christina Zdenek.
“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,” said lead author Dr. Christina Zdenek, a researcher in the Venom Evolution Lab at the University of Queensland.
“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.”
The study involved 19 snakes, representing five genetic families of reptile: an ambush elapid (Acanthophis), an active python (Aspidites), an arboreal elapid (Hoplocephalus) and two active elapids (Oxyuranus and Pseudonaja).
“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.”
The reactions strongly depended on the genus of the snakes.
“Only 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,” Dr. Zdenek said.
“The types of behavioral reactions also differed, with taipans in particular more likely to exhibit defensive and cautious responses to sound.”
“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.”
“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.”
The findings challenge the assumption that snakes can’t hear sound, such as humans talking or yelling, and could reshape the view on 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.”
“Snakes are very vulnerable, timid creatures that hide most of the time, and we still have so much to learn about them.”
The results were published in the journal PLoS ONE.
_____
C.N. Zdenek et al. 2023. Sound garden: How snakes respond to airborne and groundborne sounds. PLoS ONE 18 (2): e0281285; doi: 10.1371/journal.pone.0281285
