These innocent victims of our ignorance about their important role in the control of rodents and insects and as part of the food chain are at the top of the list of designated enemy species assumed by us. This brief article is intended to provide basic knowledge of our snakes.
Basic Types of Snakes
Snakes live on land and also in the sea. Sea snakes have flattened tail from both sides and they have usually the very long body. They need a long body as they need more air in their single but very long lungs. So they inhale a lot of air and go submerged to hunt fish. After a lapse of a considerably long time, they need to come to the surface for another large quantity of fresh air. They are of course poisonous but I do not have the information about biting a man in our country. Land snakes have a rounded tail. Because of the elongated body, some internal organs of snakes are also more or less elongate both inland as well as in sea snakes. The heart is slender or longish. There is only one lung in most snakes, which is very long. The lung forms an air sac towards the tail end. This allows air storage. However, boas and pythons have two lungs. Python’s left lung is much smaller than the right one, which is very long. Snakes inhale a lot of air and can keep it in the lung for a long time. The food gut or esophagus is also long, thin-walled and without any muscles. The prey is not chewed but swallowed head first. It is pushed into the esophagus by the forward and backward movements of the left and right lower jaws. Once it down the throat further push is brought about by the body muscles. The stomach starts from the esophagus without any distinct mark. It is also long and enormous. It is greatly distended when a large prey is swallowed. The body skin around it is then stretched and the scales separate from each other showing the skin beneath. The liver, urinary organs and genital organs are also elongated. The elongated liver is not lobed. The gall bladder and the pancreas are at the rear part of the liver. Some organs are missing in snakes, such as legs, ears, movable eye-lids, nictitating membrane, muscles of the eye-balls and urinary bladder.
Snakes swallow, not chew
The lower jaw is loosely attached to the skull. Front tips of both lower jawbones are also not united with each other. The lower jawbones are joined with the upper jaw with cartilage. This enables a snake to open its mouth very wide and swallow bigger size prey. The lower jawbones, the palate, and the upper jaws have backwardly pointed teeth. In the case of poisonous snakes fangs are present on the upper jaws. The lower jawbones work alternately forwards and backward, enabling the backwardly curved teeth to hook the food into the throat. It is then pushed into the neck portion by the wriggling movement of the neck part of the body. The location of the food remains visible as a bulge for two days or three or for more days, depending on the size of the food until it is considerably degraded or dissolved in the stomach and pushed into the intestine for digestion of soft parts. The food is digested in swallowed ‘Myna’ or pigeon takes more than ten days to be digested in summer months. After that defecation is done in a slime covering. The bones, feathers, scales, and hair are not digested.
How the non-poisonous snakes kill?
The prey is killed before it is swallowed. The python seizes its prey with a sudden dart of the head. It is held firm with its strong, sharp and backwardly curved teeth. Next, the body is wrapped around the prey two or three or more times. The prey is constricted strongly by the muscular body of the snake so that it is suffocated and its blood circulation is blocked. The snakes have a single set of muscles from head to tail on both upper sides of the vertebral column that makes the constriction very strong. After several minutes the pressure is released and the dead prey is held from its head.
How the poisonous snakes kill?
The poisonous snakes have fangs on the front side of their upper jaw instead of having a row of teeth. These are long hollow and sharp. The venom tube opens at the base of these teeth. The venom is injected deep into the body of the victim, which dies not far from the snake depending on the amount of venom injected. If the prey manages to run away for a distance or enters a burrow and dies after a lapse of time it is located by the snake.
How the prey is retrieved?
Snakes have a long slender tongue, which is bifurcated at the front end. Each part of the tongue has a pointed tip. The rear end is lodged in a sac. The sac has muscles on the outer side, which pull the sac forward whenever the tongue is protruded out of the mouth. The scale at the tip of the mouth has a concave lower edge. That enables the tongue to come out without opening the mouth. An alert snake protrudes its tongue frequently and fast as well. The tips of the tongue are chemo and thermosensitive. The sensation of slight variation in outside temperature and the chemical particles of odor or smell is carried by the tips of the tongue and touched in a pit in the front upper part of the palate or the roof of the mouth called Jacobson’s organ. The sensitive lining of the Jacobson’s organ transmits to the brain the taste or smell and the slight variation of temperature through a nerve. The snakes can find their prey even in complete darkness by feeling the heat left on the ground by a prey short time ago. Himalayan Pit Viper has even two additional pits between the nostrils and the eyes. These pits have the same sensitivity as the Jacobson’s organ. The snake comes to know when anything passes by even when it is not alert. The same quality keeps the pairs in contact. Also, this helps in escaping a predator much before a predator would discover it. The dead prey is then swallowed head first. The snake venom is digestive in nature and helps to dissolve the body of the prey faster in the stomach. The snakes do not feed if large food is present in their bodies. During the winter sleep snakes do not need to eat at all. Even when some snakes come out of their burrows during sunny days in winter, they may not eat for several days.
Being without legs snakes not only have fast or slow locomotion but also several of these are good climbers. Several species are good swimmers. Many terrestrial snakes are also good swimmers. Some species like to be in the water to keep cool, seek shelter or hunt fish, toads, frogs, and giant water bugs. Python prefers to remain completely submerged in water in the summer season during the day time to keep cool. It may keep its eyes and nostrils above the surface to catch prey on the surface or at the edge of the water. Out of the water, it creeps straight without undulating. Ribs, muscles, and skin move the body forward. Groups of ribs on both sides move alternately by lifting and lowering the skin and scutes of that side. Each group of ventral scutes gives the walking movement of the legs. Many groups of ribs on each side of the body produce waves and the body moves forward. This movement is never rapid. Most snakes show undulating movement. The snake anchors its hind part of the body to the ground and the front portion is stretched forward. The front part of the body is then anchored to the ground and hind part comes forward. This is done with the undulating movement of the long body. Some snakes move sideward as the body forms a loop on one side only, which is held fast to the ground. The rest of the body is raised above the ground. The whole body then passes through this point of contact to the ground. When the tail end reaches this point at that time the front end of the body touches the ground and the same process goes on. This is achieved through the fast group movements of the ribs.
The majority of snakes lay eggs. The eggs are covered with a soft but strong membrane. Some few snakes that give birth to tiny snakes. Their embryonic stage is completed while the egg is still in the body. So the tiny snakes hatch out of the eggs short before their birth. A female snake stops feeding much before egg-laying. It finds a suitable place for egg-laying and remains there passively. Longish eggs are laid. The eggs are hatched with atmospheric warmth. If the weather is cool the embryonic development slows down. In warmer weather incubation is faster. Usually, most snakes eggs hatching is between 30 to 50 days. Parent snakes do not play any role in the incubation. However, python female keeps her eggs under her coiled body. While sitting on the eggs the female often expands and contracts its body to produce heat for the eggs. It may even go in the sun to warm its body and to transfer some heat to the eggs.
Young snakes do not depend on their parents and look after themselves, although they have to face many enemies as compared to adult snakes. They are more active than adults and grow faster. A snake keeps growing throughout its life. However, the growth rate slows down with age. Young snakes hunt frequently. First, they eat small creatures and insects and as they grow they catch bigger animals. The skin of a snake is dry and without glands. The outer part of the skin forms scales that protect its body. With the wear and tear of the outer part of the skin, it becomes dead. The covering of the skin over the eyes does not remain clearly transparent. Snake’s skin is highly sensitive but this sensitivity also fades and finishes with the death of the outer cells of the skin. The snake becomes passive for a week or two. The dead skin is removed by expanding and contracting the body. The snake opens and closes its mouth and rubs its body to hard any surface. First, the skin is removed from the head. Suddenly the vision becomes sharp as the dull eye covering is removed. With that the snake becomes agile and the dead skin is peeled off inside out from head to tail. The bright and glossy color pattern of the body appears again. The snake becomes again active for hunting. The first removal of the dead outer skin takes place in the early part of life when the body growth rate is faster. This occurs in the first week or so after hatching. Afterward, the dead skin is removed with the growth of the body once, twice or even three times during the summer season.
Snakes have no external ears
A snake has no external and middle ear. So it cannot hear. However, as the bones of the middle ear have become connected with jaw bone which is normally attached to the eardrum. As the under part of the head and the body are directly placed on the ground any vibration from any movement or scratching on the ground nearby is communicated from the lower jaw to the brain through the auditory nerve which is connected to the internal ear. If a snake happens to be lying on a floor, any music or sound will not affect it. But if a chair is dragged on the floor the snake will respond immediately by its body movement. Swaying of Cobra with the snake charmer’s flute is not because the cobra has enjoyed the music. The snake charmer first provokes the cobra in his basket. The excited snake expands its hood and exhales loudly, at the same time darts its head forward to bluff and frighten away the provoker. As the sensitive ventral plates below the neck receive sound waves of the flute the upset snake focuses its attention on the flute. It moves its head as the snake charmer sways the flute.
Eyes are placed on the sides of the head, so these can see on both sides, but both are unable to focus on an object together as we do. Each eye has its own independent focusing. Snake makes its lens to move forward or backward to focus. Snake’s lenses are yellow which helps in night vision. Its eyesight is not sharp. It can detect moving creatures, however, things not moving become difficult to recognize, unless they are close enough to be felt by their heat.
The body temperature of the snake rises or decreases with the rise or decrease of the surrounding temperature. In winter days, as the atmospheric temperature lowers, the snakes cannot remain active as their body temperature also decreases. They look for some shelter from cold temperatures of the night in some burrow or heap of dead leaves. They remain passive in that place for the winter months. The body needs much less energy. However, even slow functioning of the body systems some energy is consumed. This energy is transferred from body fat. In late spring or early summer with the rise of atmospheric temperature, their body temperature also rises. The snakes come out of their wintering places to look for food as their body has no fat.
Poisonous or Non-poisonous
Majority snakes found in Pakistan are non-venomous. Only three categories are venomous. These categories are Cobra, Krait, and Vipers. The basic difference in poisonous snakes is that these inject poison in the victim through large fangs. The fangs are large size pair of inwardly folding sharp and hollow teeth at the anterior end of the upper jaw. The rest of the upper jaw is without teeth. In nonpoisonous snakes, the upper jaw has a number of fixed teeth and no fangs. A poisonous has a poison gland and a poison pouch or sac little below and behind the eyes. A venom tube joins the venom pouch with the base of the fang. The poison gland secretes poison into the pouch. When a snake opens its mouth to attack the poison pouch is pressed by a set of muscles that are attached to the lower jaw and the side of the skull. Cobra spreads its hood when excited or frightened. If a dead specimen is examined closely, preferably with a hand lens, 3rd and 4th upper labial scale touch the eye and the 4th upper labial scale is the largest. Krait is a glossy dark brown or black snake with white cross streaks. If a dead specimen examined closely, the mid-dorsal row of scales is hexagonal and these scales are larger than the side scales. Vipers have arrowheads. If a dead specimen examined closely, the scales on the head are similar to the scales on the backside of the body. These also overlap each other on the hind side.
Snakes avoid biting humans
Normally a snake would avoid a person coming closer. It would get waves of the steps of an approaching person through the ground. It would tend to creep away. A viper might take a defensive posture out of fear. A person gets bitten if he steps on a snake or steps too close to it. Krait would never bite during the day time even stepped on or tortured or handled.
If a person is bitten by a cobra, heartbeat and breathing slow down. Death can come in a day if the full dose of venom is injected in the blood. If a person is bitten by a Krait, the bite is slightly painful for a short period, and then it becomes painless. The venom is toxic to the nervous system. The victim gets paralyzed and death may come very soon or as quickly as 4 - 10 hours if the full dose of venom has gone in the blood. If a person is bitten by a viper soon bleeding starts due to hemorrhage of capillaries of soft parts like inside the nose or throat. Death can come in less than an hour if the victim got a full dose of venom injected in the blood. If a person is bitten by a non-poisonous snake, it is safe but if the bitten person is ignorant about the facts he or she might react in fear and maybe panic.