Snake Sensory Perception
This page is focused on the senses of snakes. It was originally written for a university project and has since been modified and adapted for this website. It is only meant to be a fairly brief guide, in time each sense will be reviewed and written about in depth and given its own page.
Royal python showing the eyes, tongue and labial pits
Sight
Generally speaking, research shows reptiles follow the fairly intuitive pattern whereby burrowing species having poor eyesight able only to distinguish between light and dark, whilst more active and arboreal species have keen eyesight for prey location. To take a random example... the royal python is a terrestrial snake with some mild inclination to climb, it is probably safe to extrapolate that it has reasonable eyesight, capable of detecting movement quite well (personal experience with the snakes supports this).
Snakes and a few other reptiles (a number of the geckos for instance) have fully fused clear eyelids which protect their eyes. This limits the movement of the eye and also means that the snakes have to focus by moving the lens closer and further from the retina, the mammalian eye on the other hand focuses by the stretching of the lens.
Smell
Snakes are famed for using their tongues to ‘taste the air’ as it is known. The tongue is in fact used to sample the air, because whilst snakes have nostrils and nasal cavities, they do not use them to smell. Snakes use the forked tongue to sample particles from the air, which are then brought in to contact with a small organ on the roof of the mouth called the "vomeronasal organ", or "Jacobson's organ." Snakes have a very keen sense of smell, and are able to assess the air far better than we are.
As such the sense of smell is very important in hunting, even a hint of rodent smell will alert the snake and it will become visibly keen and attentive. The reason the tongue is forked is the same as the reason we have two nostrils, it allows information about the direction of the smell to be detected. Ie if the smell is stronger on the right fork than the left, the snake knows the source is to the right.
Interestingly, you can assess a little about the behaviour of a snake from the way it uses its forked tongue. A snake in a new unfamiliar environment will make frequent, long drawn out ‘floppy’ flicks of the tongue, which it uses to collect as much information as possible – also seen during hunting. Whereas a snake making infrequent short flicks is likely comfortable in its environment, and is just “checking up” every now and again so to speak. A snake which senses prey will make the same short flicks, but will do them very frequently in order to quickly and constantly update information about prey location.
Hearing
Touch, or more specifically sensing ground vibrations is very important to snakes in general, providing a primary sense in hunting. The nature of the snake hearing mechanism has been the topic of some debate, and its only in fairly recent years that it has been acknowledged snakes are capable of sensing both ground vibrations and, in some snakes at least, air vibrations (sound). Recent studies provide evidence that snakes the two sensory inputs result in brain activity.
Whilst snakes lack the external ear, they do have a functional, adapted inner ear, complete with cochlea (the auditory part of the inner ear). They are often seen resting their lower jaws upon the floor in order to pick up ground vibrations. The proposed mechanism for this is that the jaw passes vibrational information to the stapes via the quadrate.
Infrared vision
Infra-red vision is the first sense we chose to write a more detailed account for, which you can see here: Infrared vision in snakes
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