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Snakes sense the world in very different ways than humans
do. But what do I mean by feeling sounds and tasting smells?
The Five Six
Senses
Touch
 A snake's sense of touch is highly developed. What else
would you expect from an animal that does everything on its belly? Despite
being covered in scales, snakes are highly sensitive to touch and can sense
very slight vibrations through the ground. A snake will feel your presence long
before it sees you.
Hearing
"But snakes don't have ears!" someone exclaims. But that is
only partially true.
Snakes do not have external ears. External ears would be too
cumbersome for a snake (especially since it's theorized that snakes evolved out
of the necessity to become more efficient burrowers, and what better way than
to get rid of those obtrusive and unwieldy limbs?) They do, however, have inner
ears that allow them to hear low-frequency sounds that vibrate through the air.
What about all those non-low-frequency sounds?
All the vibrations that a snake feels from the ground are
transmitted through its body and to the quadrate bone, which connects the jaw
to the skull. The quadrate connects to the middle ear, which is connected to
the inner ear. Thus, due to a snake's sense of touch, its sense of hearing is
highly acute.
Taste and Smell
When a snake quickly moves its tongue in and out of its
mouth, it picks up various particles from the air and surrounding objects and
can therefore taste the things around it. When a snake breathes air flows in
and out of its nostrils, but it doesn't smell a thing. That is because snakes
don't smell with their noses. They smell with their tongues.
 The vomeronasal organ, more commonly known as the Jacobson's
organ, is the sensory organ dealing with smells. It is present in most animals
and is found at the base of the nasal cavity. In snakes, the receptors of the
organ are located at the roof of the mouth. The particles collected by the
tongue from the air or surrounding objects are transferred to the organ when
the tongue retracts.
A forked tongue allows the snake to determine in which
direction the tastes and smells are coming from.
Sight
The sense of sight is highly varied in snakes. Vision ranges
from nearly blind to very keen eyesight. The level of development of a snake's
vision is generally dependent on the snake's lifestyle.
Fossorial snakes spend the majority of their time in the
dark. They don't require good vision. Their other senses are so well developed
that the snakes can find food and detect dangers without seeing. Many of these
snakes can only sense the difference between light and dark.
 The best vision is found in arboreal snakes. Some snakes
have binocular vision, which means that they can focus both eyes on the same
object. Because arboreal snakes can live high in the trees, they can use their
acute vision to locate potential prey or predators from far away. Good eyesight
is especially useful when catching birds that are flying by.
For other snakes, vision is generally adequate. Most of
these snakes live on the ground where there are often obstacles to obscure
vision, making keen eyesight relatively useless. They lack the ability to
sharply focus their eyes, so vision is usually movement-based.
Snakes don't have moveable eyelids. But there is a
protective transparent lens that covers the eye. The loss of moveable eyelids
may have been an evolutionary modification to help deal with the difficulties
of a fossorial or aquatic lifestyle. Because of this modification, it is
difficult to tell if a snake is sleeping or if it's just sitting still.
Infrared
Many snakes within the families Boidae and Viperidae have
infrared-sensitive pits. Also known as heat pits, they can sense the heat
radiating from animals and objects surrounding them. So far, research has determined that a
snake's heat pits can sense heat as far as 30 feet away and are sensitive
enough to detect temperature changes of less than .001 degree Celsius.
Herpetologists originally thought that infrared-sensitive
pits evolved in some snakes to modify and improve hunting methods. Recent
observation has shown, though, that the primary function of the pits is in
thermoregulation. The snakes can determine which objects around them have been
warmed enough by the sun or have been cooled enough in the shade and can then
regulate their body accordingly. Detecting prey is a secondary function.
Next Time
Snakes use all of their senses to help them find food. In my
next blog entry I will discuss how snakes hunt and eat.
Thanks for reading!
Other Blog Entries:
New Animal Attractions
Reptiles: A Scaly Introduction
Snakes: They're All Around
Snakes: A Family Affair (Part 1)
Snakes: A Family Affair (Part 2)
Snakes: Clever And Deadly Behaviors
Snakes: Do The Locomotion (Part 1)
Snakes: Do The Locomotion (Part 2)
Snakes: A Look Inside
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