General Facts about Snakes
The largest snakes in the world are members of the family Boidae, which includes the boa and the python. Some members of this family never attain a length of more than 0.6 m (2 ft), but the largest may grow to more than 9 m (30 ft). Sea snakes have no gills and must rise to the surface for air, but they can remain underwater for several hours, obtaining dissolved oxygen from water that they swallow and eject. Approximately 2500 different species of snakes are known. Approximately 20 % of the total number of the snake species are poisonous. The big pythons can eat animals that weigh up to about 68 kg (150 lb), but swallowing such a meal is a difficult process. The snake must bite to inject its venom; no snake has a stinger in its tail. Three species of snake can spit or eject the venom in a fine spray, which is aimed at the eyes of an enemy and projected for distances up to 2.4 m (8 ft). If the venom gets into the eyes, it may cause blindness. The spitting is used only in defense and never to obtain food. Vision is well developed in most snakes, but many burrowing snakes are virtually blind. Snakes have a strong sense of smell, which is relied on to a large extent in hunting food. Snakes find their prey by sight and scent, and sometimes temperature. Except for burrowing species, snakes have excellent short-range vision. Their sense of smell is extraordinary, thanks to a harmless, constantly flicking forked tongue that carries scent particles to a specialized sensory organ ('Jacobson's organ') on the roof of the mouth. Snakes are deaf to airborne sounds. The Cobra does not hear, as it is believed, the snake-charmer’s flute. They can, however, feel vibrations through the ground or whatever they are resting on. Snakes move slower than an adult human can run; the fastest recorded speed achieved by any snake is about 13 km/hr (8 mph), but few can go that fast. Depending on the species, snakes may be egg-layers or give birth to live young. They generally mate in the spring, shortly after leaving whatever hollow, burrow or rock crevice has sheltered them through winter hibernation. Egg-layers usually deposit groups of eggs in dirt, beneath stones or logs, or in piles of decaying wood or vegetation during late spring or early summer. Most snakes hatch or are born in late summer. Whether deposited as eggs or dropped as fully formed miniature adults, snakes are on their own from the start. Snakes do not take any responsibility for the care and protection of their young. Most snakes mature at one or two years of age, and individuals may live up to twenty years in the wild. The greatest age known for any snake is just under 30 years, attained by both the anaconda and the black-lipped cobra. Black and green mambas both produce neurotoxins, which is why they kill so fast. Black mamba is more venomous. Neurotoxin inhibitors and antivenin are generally made from the venom of the same snake, but it is likely that antivenin from one would be at least partially effective against the other. Because these are two different snakes their venom has to be different and thus the antivenin from one may not act for the other. Snakes do not leap or jump into the air. Instead, those that do strike out coil themselves enough to get a push or strong outward movement designed to snatch prey or inject venom. Most snakes can only strike about one half their total body length. They do not actually leave the ground. They are capable of striking upward or outward at approximate one half length level. Snakes are more closely related to lizards than to other reptiles, and probably evolved from a single group of lizards. Curiously, they probably did not evolve from the group of legless lizards. In ancient Greece, the sick and injured sought the aid of the god of healing and medicine, Asklepios. They took an offering to the temple and waited for the god to come to them in their dreams, or to send his sacred servants, the snakes. Ancient writings tell of the snakes healing with a touch of the tongue. The snake in question was the Aesculapian snake. The Romans chose to import this snake to their own temples, rather than to bring in Greek healers. The snake today forms part of the symbol of physicians and veterinarians (the snake is wrapped around Asklepios' staff), linking snakes to millennia of healing and medical practice. The hognosed snake (Heterodon sp.), grass snake and the spitting cobra can feign death by flipping on to their backs when threatened. They open their mouths, allow their tongues to loll and can empty a foul smelling substance from their anal glands, making them highly unappetizing to any potential predator. Many snakes, such as vipers, boas and pythons have temperature-sensing organs on their heads. These heat pits are sensitive to changes in temperature of as little as 0.002 degrees Celsius, and effectively allow the snake to navigate and hunt in the dark. Snakes can have over 300 pairs of ribs. Snakes turn “blue” before a shed. This opaque change to the skin is actually due to the presence of a lymph-like layer of fluid between the old and new skins, prior to the shed of the old skin. Reports of the longest, heaviest and oldest reptiles abound. Many cannot be verified. A reticulated python, shot in Indonesia in 1912, was said to be 32 feet 9 1/2 inches in length. One Burmese python weighed in at over 400 pounds. Although seldom as long as the giant pythons, the green anaconda is a heavier snake. Sir Percy Fawcett is said to have killed an anaconda measuring 62 feet in 1907, in Brazil. Since the early part of the last century, the New York Zoological Society has offered a reward of $50,000 for the capture of a live snake greater than 30 feet in length. The oldest recorded snake is a boa constrictor named Popeye, who died in 1977 at the age of 40 years, 3 months and 14 days. The smallest snake may be the Martinique thread snake (Leptotyphlops bilineatus), which does not grow any bigger than 4 1/4 inches. A snake's internal organs, although superficially different, have basically the same functions as those of a mammal. The difference lies in their arrangement. They are placed one after the other, to accommodate the tube-like body. All snakes have a right lung and associated air sacs that extend most of the way to the vent. In most species, the left lung is considerably shorter, or even missing. The glottis, which is the entry to the trachea (breathing tube), can move to either side, to allow the snake to swallow prey. This is the tube you see when you look at the floor of a snake's mouth. Cartilage around the opening of the tube closes to prevent food from entering the respiratory tract, and produces the classic “hiss” in many snakes. A snake's heart can slide 1 to 1 1/2 times its length from its normal position, to allow the passage of swallowed prey. This is because of the relative mobility of the pericardial sac, which surrounds the heart. Venom glands have evolved independently in several species. Venoms are very complex substances, which may consist of a dozen or more toxic components. These can include substances poisonous to the heart, nerves and DNA as well as enzymes that break down natural tissue barriers, allowing the spread of venom within the body. Spitting cobras can inject venom in their bites, but can also force venom out, under pressure, through tiny channels in their fangs. Raising the front half of its body, the snake can aim venom at the eyes and mucous membranes of its target, over 3 feet away. Snakes have two rows of teeth on the top jaw, one row on the bottom jaw. The teeth, including fangs, in most cases are replaced throughout life. When the tongue is in the mouth, it lies in a sheath beneath the glottis with its tip touching the vomeronasal or Jacobsen‘s organ. This is an organ of smell, so when your snake flicks out his tongue, he is, in fact, “tasting” or smelling the air. The forked design allows the snake to detect on which side the smell is strongest, and so to locate his prey, even in the dark. The Brahminy blind snake are all females. When mature, they lay fertile eggs, and the young are clones of the mother. Although native to Asia, this snake is now found in warm countries all over the world. The Emerald tree boa is born red or yellow, and changes to green after about a year. The rattlesnake's rattle consists of six to 10 layers of scales, which fail to shed and make that distinctive sound when the tail is shaken as a warning. Eventually the older segments will slough as the rattle lengthens. The tail of the Calabar ground boa is blunt, cylindrical and has white scales on the underside, and altogether appears very much like a head. When threatened, the snake coils into a ball, hides its head, leaving the less vulnerable tail exposed to confuse predators. The common egg eater (Dasypeltis scabra) is a highly specialized snake. Although it is not venomous, the markings are sufficiently similar to those of the deadly cobra or viper that a potential predator will think twice before attacking. The egg eater can also expand its jaws to mimic the larger head of the venomous. To consume an egg, the jaws can expand to four or five times the size of the egg. Once engulfed, the egg is pierced by two specialized vertebrae. Other modified bones in the vertebral column stabilize it, prevent its slipping out of the mouth or further into the snake. Yet another set of unique vertebrae crush the egg. Once emptied of its contents, the shell is regurgitated. The black mamba (Dendroaspis polylepsis) is brown, gray or olive, but never black. It is a particularly dangerous snake, with a bite that kills 95 to 100 percent of victims. The black mamba may also be the fastest snake, reaching speeds of 10 to 12 miles per hour. Other particularly dangerous snakes include the common krait, Russell's viper (both Asian snakes) and the taipan (Australian). Seven of the 10 most deadly snakes live in Australia. Snakes move by relaxing and contracting muscles lengthwise along the body. Sidewinding is a specialized form of motion that allows a snake to travel with speed and relatively little expenditure of energy along loose desert sand. The snake lifts a loop of its body from the surface, using its head and tail. The loop is moved sideways and then back to the ground. This creates the typical series of unconnected parallel tracks. The paired claw-like structures seen on either side of the vent of a snake such as a ball or royal python, are in fact, remnants of the legs present in the animals from which the modern species has evolved. |
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