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. Snakes

 

 

Sight: . . . . .. . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Considering their predatory nature, the eyes of snakes are relatively inefficient, but like other animals with poor eyesight they make up for this apparent disability by having other extremely sharp senses.

In general, a snake’s eyesight can be said to be poor when compared with ours or even with that of most lizards. Due to the absence of a retinal fovea they have a reduced ability to focus and their perception of detail is poor.

The eyes of snakes have no movable eyelids, but the cornea is protected by a circular transparent scale (or, in some cases, a transparent part of a larger scale) known as the brille or spectacle.

Hearing: . . .. . . . . . . . . . . . . . . . . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . It is a well-known fact that snakes do not posses external ears, nor in fact do they possess a tympanum or eardrum. However, snakes apparently can hear as they react to noises of varying degree and pitch. The snake’s method of hearing is by picking up vibrations from the solid surfaces on which they rest. The vibration pass through the snake’s jawbone to the quadrate and hence to the stapes, which is in close proximity to it. From there nerve impulses are transmitted to the brain in the usual manner. It is suspected that the long is also involved in the transmission of sound and other vibrations.

Smell and Jacobson’s Organ . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . If an animal is oriented to any particular sense (it is probable that our main sense of orientation is our sight), then the snake is surely oriented by its sense of smell. Snakes mainly rely on what to us can be regarded as a roundabout way of detecting odours. Situated in the palate just below the nose and corresponding to but not adjoining the nostrils is a pair of domed cavities lined with sensory epithelium connected to a special branch of the olfactory nerve. These vomeronasal pits are known as Jacobson’s organs and are used to detect scent particles that are introduced to them by the tongue. It is believed that the tips of the highly mobile forked tongue are designed to fit into the organs. The scent particles are picked up from the air or solid objects on the tips of the tongue and transferred directly to the inner surfaces of the Jacobson’s organ from whence the necessary messages are passed to the brain. This sophisticated sense of smell is highly important to snakes, which use it to find prey, to seek out a mate, and to detect potential enemies.

Balance and Touch: . . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The sense of balance in snakes is quite highly developed and arises from both the semicircular canals that respond to head movements and the muscles as they are affected by changing gravitational stresses as other parts of the body are tilted.

The sense of touch is also highly developed. One has only to lightly touch a resting captive snake on any part of its body and note the reaction, which will range from a twitch of the area touched to angry defensive action or attempt at flight, depending on the species of snake and its degree of tameness.

Heat-sensitive Organs: . . . . . . . .. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . A highly specialized sense organ found only in two families of snakes is the heat-sensitive pit or organ. In the Boidae, all members of the subfamily Pythoninae (except Aspidites and Calabaria), and the genera Corallus, Epicrates, and Sanzinia of the subfamily Boinae have these organs arranged in series along the jaw line, either within the labial scales (Pythoninae) or between them (Boinae). All members of the family Crotalidae (also known as pit vipers) possess a single pair of prominent pits, each located between the eye and the nostril. These heat receptor pits are extremely sensitive to temperature changes, and snakes possessing them are able to locate the direction of warm-blooded prey, even in complete darkness, and strike at it accurately. Pit vipers can detect temperature variation of as little as 0.003°C and Boids are slightly less sensitive at 0.026°C.