Snakes (Sub-order Serpentes)

Snakes can be classified into 4 groups according to their dentition (fangs).

- Group 1: solid toothed non-venomous snakes:

  • No venom.
  • Have teeth on upper and lower jaw.
  • A very painful bite (African rock python, large mole snake).
  • Blind snakes have no teeth on the lower jaw, feed on termites and other vertebrates.
  • Worm snakes have no teeth on the upper jaw, feed on termites too.
- Group 2: Back fanged snakes:
  • Have 1 to 3 pairs of recurved, grooved fangs situated towards the back of the upper jaw. The venom groove is at the front edge of the fangs.
  • Haemotoxic venom
  • Only the Boomslang, the Vine snake or the Twig snake have a medical importance.
- Group 3: Fixed front fanged snakes:
  • Have normal teeth as well as a pair of short, erectile fangs situated in the front of the upper jaw.
  • Fangs are specialised, tubular to allow injection of venom.
  • Fangs of the Spitting snakes are modified so that the ejected venom is forced up and away from the snake's fang, rather than downwards.
  • Venom of Elapids (Cobras, Rinkhals, Mambas) is neurotoxic.
- Group 4: Hinged front fanged snakes:
  • Adders
  • Have 1 pair of large, functional fangs at the front of the upper jaw which are equipped with a hinge mechanism. Without this mechanism, the fangs would otherwise pierce the lower jaw when the snake closes its mouth.
  • Fangs are only erected once the mouth is opened in preparation of biting.
  • Have fangs sheaths at the back end of each fang.
  • The Puff adder is responsible for most of serious snakebites in South Africa.
  • Cytotoxic venom.

Definition of a snake:
Usually, snakes are specialized legless lizards, have no external ears and eyelids, their tongue is retractile into a sheath, have long back bones with many articulated ribs. They are carnivorous and their preys are swallowed alise, they subdue the prey with injection of venom or by constriction. Their tail cannot be shed. They shed their skin. They lay eggs. We can find more than 150 species of snakes in Southern Africa and 37 have frangs and venom, causing harm to human beings.

They have a good vision but ignore stationary prey (except for the Boomslang and the Twig snake). They have not movable eyelids but their eyes are covered with a fixed transparent shield that's shed with the rest of the skin during moulting.

They are unable to hear but feel the vibrations in the ground.

The snake pushes its tongue out through a groove in the front of the mouth, as it flicks up and down, it picks up various particles in the air. When the tongue is retracted back into the mouth, these particles are deposited onto the organs of Jacobson situated in the roof of the mouth. This informs the brain exactly what the snake is smelling.


  • 15 times/year in juvenile snakes
  • about 3/4 times /year in adults, depending of the growth rate, irrespective of the time of the year.
Just before shedding, the skin over eyes becomes opaque, it may go into hiding, due to restricted vision and vulnerability to predators. To start, it rubs its nose against a rough surface until a piece of skin comes loose.

4 basic ways in which snakes move:

  • Rectilinear: It progresses slowly forwards in a straight line using scales on underside of body pushing forwards in waves like a caterpillar. Ventral scales are in contact with the ground that grip and pull snake forwards. Often Pythons and Puff adder.
  • Sidewinding: Used only by few desrt welling species to allow for movement accross moving sand. Only 2 section o body touch the sand at any time. Advantage: Most of the body doesn't touch the hot sand.
  • Serpentine: Normal movement. Used when disturbed or when chsing their prey. It undulates horizontally forcing rear edges against the ground. The body is pushed forwards in direction that the snake wants to go. It's the same when it is swimming.
  • Concertina: When the snake's movement is restricted as in tight spaces or when they have difficulty in negociating smooth branches.
Snake don't exceed 20 km/h (except the Black mamba). They don't receive a very good supply of oxygenated blood and tire easily when they force to exercise more.
The fastest snake is the Yellow-bellied sand snake.

Snakes are POIKILOTHERMIC: they have no internal mechanism to control their own body temperature, they are dependent on their immediate environment for their heat requirement.
In areas where ther is a real difference in temperature between summer and winter, snakes will go into hibernation for as long as the cold prevails. During hibernation, they accumulate fat.
In warm winter's day, a snake basks near its hideout. They hibernate in holes made by other animals, beneath rocks or in deserted termites mounds.

They mate early in the spring, the male locates the female by scenting. 4-8 weeks after mating, eggs are deposited in hollow tree trunk, rotting vegetation. From 4-60 eggs or more. The eggs need heat and humidity in order to incubate, they hatch 2 or 3 months later. The young snakes are equipped with an egg tooth, used to split the egg from inside. this tooth is later shed. Hatchlings of venomous species are equipped with fangs and venom gland from birth.

Snakes that produce live young are:
  • Mole snakes
  • Puff adder
  • Gaboon adder
  • Berg adder
  • Horned adder
  • Rinkhals
  • Common slug-eater
  • some blind snakes
More snakes show no further interest in their offsprings except for a few species, such as the Pythons which assist with incubation.

It is produced and stored in modified salivary glands that are situated on either side of the head, behind the eyes. It is used both to kill the prey and to assist with digestive processes. Snakes have 1 venom type except the Mozambique spitting cobra and the berg adder which have both cytotoxic and neurotoxic venom.

3 venom type:
  • Haemotoxic: Causes continued bleeding due to a defect in the ability of blood to coagulate. Snakes with grooved back fangs. Boomslang, Vine snake, Twig snake.
  • Cytotoxic: Adders. Leads to tissue destruction around the site of bite with localised bleeding. Snakes with hollow hinged front fangs.
  • Neurotoxic: Cobras, Mambas. Affects the nervous system, causes paralysis of muscles, difficulty breathing, nausea and vomiting. Snakes with fixed front fangs.

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