Even without visible ears, snakes are anything but deaf. A study in the trade journal "PLOS One" shows that the animals not only perceive the smallest vibrations over the ground, but also sound over the air.
Snakes have an inner ear but no eardrum, said the biologist and reviewer of the study, Ulrich Joger, of the German Press Agency. Some textbooks still say that snakes are deaf. In science, however, one already suspected that this was wrong, said Joger, former director of the State Natural History Museum in Braunschweig.
It was previously known that snakes sense ground vibrations by laying their heads on the ground. Joger explains that concussions vibrate both halves of the lower jaw. These vibrations would then be transmitted through a series of bones to the inner ear.
Response of snakes depends on species
Australian researchers have now investigated whether snakes also react to sound in the air. The experiment included 19 captive-born animals from six different species that are mainly found in Australia: from the woma python, which can be up to three meters long, to the taipan, one of the most venomous snakes in the world, to the brown snake, also very venomous .
Three different sound frequencies were played to the reptiles in a soundproof room, explain the researchers led by Christina Zdenek from the University of Queensland in Brisbane, Australia.
They observed how the snakes reacted, paying attention to body, head, jaw, tongue and hissing sounds. One of the frequencies produced ground vibrations, the other two sound waves in the air. The reaction of the snakes was strongly dependent on their species.
While the boa snake Woma moved toward the sound, the smaller poison snakes tended to move away from it, the study says. The nocturnal woma python has few natural enemies. That's why she doesn't have to be as careful as smaller species and tends to move in the direction of the noise. Taipans, on the other hand, have to protect themselves from birds of prey, for example, and are therefore probably more sensitive to noise. But Joger said too few snake species were part of the experiment to really support such an interpretation.