Snakes use inner ear to locate prey

New York, Feb 26 | Updated: Feb 27 2008, 05:23am hrs
Snakes cant hear as they dont have an ear, it is often believed. But, a new study has found that the reptiles do possess an inner ear with a functional cochlea which they use to detect vibrations caused by prey.

A team of international researchers has carried out the study and found that the ears of the snakes are sensitive enough to not only hear the prey approaching, but also to allow the brain to localise the direction it is coming from.

According to the researchers, any disturbance at a sandy surface leads to vibration waves that radiate away from the source along the surface. These waves behave like ripples on the surface of a

pond after a stone is dropped

into water.

However, these sand waves propagate much quicker (the speed is about 50 metres per second) than at water surface. But on the other hand, much more slowly than, for instance in stone and the amplitude of the waves may be as small as a couple of thousands of a millimetre.

Yet, a snake can detect these small ripples. If it rests its head on the ground, the two sides of the lower jaw are brought into vibration by the incoming wave. These vibrations are then transmitted directly into the inner ear by means of a chain of bones attached to the lower jaw. This process is comparable to the transmission of auditory signals by the ossicles in the human middle ear. The snake thus literally hears surface vibrations, the studys lead author J Leo Van Hemmen of the Technical University, Munich was quoted by the ScienceDaily as saying.

In their study, combining approaches from biomechanics and naval engineering with the modelling of neuronal circuits, the team has shown that the snake can use its ears to perform the same trick for sound arriving through sand.

PTI