Snakes

Snakes are limbless reptiles with long, cylindrical bodies, scaly skin, lidless eyes, and a forked tongue. Most species are not poisonous, some are mildly poisonous, and others produce a deadly poison. The term venom is commonly used to describe the poison produced by a snake.

All snakes are carnivores (meat-eaters) and cold blooded, meaning their body temperature is determined by the environment rather than being internally regulated. For this reason, snakes are found mainly in tropical and temperate regions, and are absent in cold climate zones.

Types of snakes

The 2,700 species of snakes fall into four superfamilies: Boidae (boas, anacondas, and pythons), Elapidae (cobras, coral snakes, mambas, and kraits), Colubridae (king snakes, water snakes, garter snakes, black snakes, and adders, to name only a few) and Viperidae (true vipers and pit vipers).

Members of the Boidae family are among the most primitive of all snakes. They are constrictors that kill their prey by squeezing it to death. Some of the largest snakes are members of this family. Some anacondas, for example, have been known to grow to more than 11 meters (37 feet) in length.

Snakes in the Elapidae family have grooved or hollow fangs in the front of the mouth. The bases of the fangs are connected to the venom gland. Venom is injected when the victim is bitten. Members of this family range in size from the tiny elapids, which may be no more than a few centimeters long, to the feared taipan, which may grow to nearly four meters (12 feet) in length.

The Colubridae family is huge, with more than 1,400 species, and includes the majority of living species. Most colubrids are harmless, but a few are extremely dangerous. Examples are the rear-fanged snakes, such as the African boomslang or the crown snake. These snakes do not release their poison through hollow fangs. Instead, they inject poison by chewing their prey after it is in their mouth.

Members of the Viperidae family are among the most dangerous of all snakes. They include in addition to the vipers themselves the rattlesnake, fer-de-lance, and bushmaster. Most members of the family have a wedge-shaped head that people have come to associate with poisonous snakes.

Anatomy and physiology

Snakes have extremely poor sight and hearing. They detect their prey primarily by means of vibrations, heat, and chemical signals they detect with their other senses. For example, a snake's flicking, forked tongue acts as a chemical collector, drawing chemical "smells" into the mouth. Those smells are then analyzed by two chemical sensors known as Jacobson's organs on the roof of its mouth. This mechanism also allows male snakes to detect females in the reproductive state.

Words to Know

Carnivore: A flesh-eating animal.

Jacobson's organs: Chemical sensors located on the roof of the mouth of a snake used to detect chemical "smells."

Molt: To shed an outer layer of skin at regular intervals.

Venom: A poison produced by a snake.

Another mechanism used by snakes to detect prey is a set of tiny pits or hollows that certain kinds of vipers have on the side or top of their heads. These pits can detect the body heat of prey at considerable distances.

Contrary to popular belief, snakes are not slimy. The scales that cover their bodies are dry but glistening, giving a sheen that offers an appearance of wetness. Scales protect the snake's body from friction and dehydration. They also aid its movement by gripping the surface while powerful muscles propel the body forward, usually with a horizontal waving motion. This method of movement means that snakes cannot move backward.

Instead of eyelids, the eyes of snakes are covered and protected by clear scales. Several times a year, snakes molt, shedding their skin in one complete piece by rubbing against a rough surface.

Snakes' teeth do not allow them to chew and break up the bodies of their prey. Instead, they usually swallow their prey whole. Special ligaments in the snake's hinged jaw permit its mouth to open to as much as a 150-degree angle. Thus, the snake can swallow animals many times larger than the size of its own head. The largest recorded feast was a 130-pound (59-kilogram) antelope swallowed by an African rock python.

Snakes' teeth face inward and prevent the prey from escaping. The snake's strong jaw and throat muscles work the food down the esophagus and into the stomach, where digestion begins. Digestion time differs, and is influenced by temperature. In one instance, a captive python at a room temperature of 30°C (87°F) digested a rabbit in four days. At cooler temperatures (18°C; 64°F), however, digestion took more than two weeks.

The interval between meals also varies. Some snakes go weeks or even months without food. In temperate climates, snakes may fast and hibernate during the winter months. Pregnant females may hibernate and fast seven months, while both sexes fast before shedding.

Hunting and defense

The coloring of a snake's skin scales provides an excellent camouflage from predators and prey. Tree snakes can have a color as green as any leaf in the forest; ground snakes are as brown or dusty grey as the earth and rocks; and sea snakes are dark above and light beneath. Some snakes are brightly colored with vivid patterns that warn potential predators to stay away. An example is the highly venomous coral snake, which has orange, black, and white rings.

Snakes attack only when hungry or threatened. When frightened, they tend to flee. If there is no time for flight, or if snakes are cornered or antagonized, they strike. Venomous snakes have two fangs in the upper jaw that penetrate the flesh of their prey. Poison glands then pump venom through grooves inside the fangs into the prey. Some species of snake inject their prey with toxin and wait until the animal is no longer capable of struggling before eating it. Snake venom is purely a feeding aid, serving both to subdue the prey and to aid in its digestion before it is swallowed.

Nonvenomous constrictors, such as boas, pythons, and anacondas, first snatch their prey in their jaws. Then, with lightning speed, they coil their bodies around the animal, squeezing its thorax to prevent breathing. Amazingly, the prey's bones remain unbroken during this process.

Snakes and humans

Snakes have fascinated and frightened humans for thousands of years. Some cultures still worship snakes, seeing them as creators and protectors. Other cultures fear snakes as devils and symbols of death.

In many ways, snakes serve a valuable function for human societies. They prey on animals, such as rats and mice, that we often regard as pests. Many people enjoy keeping snakes as pets also.

On the other hand, many people have a terrible fear of these reptiles. They may believe that the only good snake is a dead snake. Unfortunately, this attitude leads to the death of many harmless snakes. Yet, as much as most humans fear snakes, snakes fear humans more. Certainly, some snakes can kill a human in a matter of minutes, and no snake should be handled unless positively identified as harmless. However, the estimated risk of venomous snakebites to humans in the United States is 20 times less than being struck by lightning. Overall, a well-educated, healthy respect for snakes would benefit both humans and snakes.

[See also Reptiles ]

snake proverbial allusions to the snake focus on its venomous bite as representing a lurking danger; it is a type of deceit and treachery, as with reference to the fable by Aesop, in which the man who had warmed a chilled snake in his own bosom was bitten for his pains. The word is recorded from Old English (in form snaka) and is of Germanic origin.

Snakes are the emblems of St Patrick, who was said to have banished them from Ireland.
snake charmer an entertainer who appears to make snakes move by playing music, although the snake is in fact following the movement of the player's instrument rather than the sound of the music. The image is of longstanding, as in the biblical reference in Psalm 58:4–5.
snake in the grass a treacherous or deceitful person. The expression comes originally from Virgil's Eclogues.
snake-oil a term for a substance with no real medicinal value sold as a remedy for all diseases.
snakepit a pit containing poisonous snakes; in early legends, used as a means of execution, as in the story of Gunnar, who is said to have been put to death in this way by Atli.

In the 20th century, the term has been used for a scene of vicious behaviour or ruthless competition, and specifically (after the title of a novel (1947) by M. J. Ward), a mental hospital.
snakes and ladders a children's game in which players move counters along a board, gaining an advantage by moving up pictures of ladders or a disadvantage by moving down pictures of snakes; the game was put on the market in the early part of the 20th century.
snakes in Iceland an allusive phrase referring to something posited only to be dismissed as non-existent; the reference is to Dr Johnson's comment on Horrebow's Natural History of Iceland (1758), to the effect that ‘he could repeat a complete chapter…the whole of which was exactly thus:—“.Chap. lxxii. Concerning Snakes. There are no snakes to be met with throughout the whole island”.’

snake common name for an elongated, limbless reptile of the order Squamata, which also includes the lizards. Most snakes live on the ground, but some are burrowers, arboreal, or aquatic; one group is exclusively marine. In temperate climates they hibernate. They are generally solitary in their habits, although they may congregate in places offering food or shelter, and large numbers may hibernate together. Snakes range in length from about 4 in. (10 cm) to over 30 ft (9 m). Most are protectively colored.

Characteristics

Anatomy

Snakes constitute the suborder Serpentes (or Ophidia). In most snakes limbs are entirely lacking, but a few have traces of hind limbs. The skin, which is covered with horny scales, is shed, usually several times a year. The extremely long, narrow body is associated with distinctive internal features. The number of vertebrae is much larger than in most vertebrates, paired internal organs are arranged linearly rather than side by side, and only one lung is developed, except in members of the boa family, which have two lungs. The jaws of snakes are loosely jointed and extremely flexible. The pointed, backward-curved teeth are fused to the supporting bones of the head. There are no ears or movable eyelids. Snakes have good vision. They do not hear airborne sound waves, but can perceive low-frequency vibrations (100-700 Hz) transmitted from the ground to the bones of the skull. A chemosensory organ opens into the roof of the mouth; it receives stimuli from the forked tongue that constantly tastes the surroundings as the animal moves along. Snakes have no larynx or vocal chords, but are capable of producing a hissing sound.

Locomotion and Limblessness

A snake moves by means of muscular contraction, which can produce several types of locomotion, the commonest types being undulation and straight-line movement. Straight-line movement is aided by the ventral plates, elongated scales on the abdomen that overlap with their open ends pointing toward the tail. These plates can be moved forward by means of muscles attached to the ribs.

It is believed that snakes are descended from lizards, but how and why they evolved toward limblessness is uncertain. Some paleontologists have held that limblessness was an evolutionary advantage in the dense vegetation that formed the early environment of snakes, or that it developed to facilitate burrowing habits, but others believe that the earliest snakes evolved in a marine environment and are descended from marine lizards. Support for the latter view comes from recent discovery of the most primitive snake now known, a fossil specimen with two short but well-developed hind legs found in marine sediments in Israel. It lived in a shallow sea 95 million years ago.

Predation

Small snakes feed on insects and larger ones on proportionately larger animals. Their teeth are designed for catching and holding prey, but not for chewing. The construction of the jaws, the ribs, and the expandable skin enable them to swallow very large prey whole. Some snakes capture animals by pinning them to the ground; some—the constrictors—crush them by wrapping their bodies around them and squeezing; still others—the venomous snakes—inject poison into their victims. The poison, or venom , is produced by modified salivary glands from which it passes through either a groove or a hollow bore in the fangs, the enlarged, specialized teeth found in venomous snakes. A snake may bite a person when threatened or alarmed; if the snake is venomous the bite can sometimes prove fatal (see snakebite ). Only by familiarity with the appearance of particular species, or by examination of the fangs, can the venomous snakes be distinguished from the harmless ones.

Reproduction

Fertilization is internal in snakes; as in lizards, the males have paired copulatory organs, either of which may be used in mating. Females of some species can store sperm for several years to insure future fertilization. In most species the female lays eggs; in some the eggs are incubated and hatched within the mother's body; in a few there is true viviparity, or live birth, with the young nourished by means of a placenta rather than an egg. Some egg-laying snakes brood the eggs, but there is no parental care of the young.

Types of Snakes

The approximately 2,700 snake species, of which about four fifths are nonvenomous, are distributed throughout the temperate and tropical zones of the world (except in New Zealand, Ireland, and some isolated oceanic islands) and are found in greatest profusion in the tropics. About two thirds of all snake species belong to the family Colubridae; most of these are nonvenomous. Among the harmless colubrid snakes of North America are the garter snakes (including the ribbon snake), the water snakes, the green, or grass, snakes, the black snakes , the racers , the king snakes (including the milk snake), and the bull, hognose, and rat snakes. The family Boidae ( boas and pythons ) includes the world's largest snakes, the South American anaconda and the Asian reticulated python, as well as the smaller boa constrictor and the tree and sand boas.

Most poisonous New World snakes belong to the pit viper family; these include the copperhead , water moccasin , rattlesnake , fer-de-lance, and bushmaster . Venomous Old World snakes are the true vipers , including the adder and the asp , and members of the cobra family, including the mamba of Africa and the krait of Asia. The poisonous coral snakes of the New World also belong to this family. The venomous sea snakes inhabit tropical oceans.

Importance

Snakes are of major importance as pest controllers because of their extensive predation on destructive mammals such as rats and mice. Some, like the sea snakes and pythons, are highly regarded as food in Asia but, although most are probably edible, snakes are not widely used for meat. The skin is often used for belts, bags, and shoes. Venom is removed from snakes for use in treating certain diseases and to make antivenin for snakebites.

See also snake worship .

Classification

Snakes are classified in the phylum Chordata , subphylum Vertebrata, class Reptilia, order Squamata, suborder Serpentes.

Bibliography

See A. H. and A. A. Wright, A Handbook of Snakes of the United States and Canada (2 vol., 1957); K. L. Williams and V. Wallach, Snakes of the World (2 vol., 1990).

snake Any of c.2700 species of legless, elongated reptiles forming the suborder Serpentes of the order Squamata (which also includes lizards). There are 11 families. They range in length from c.10cm (4in) to more than 9m (30ft). There are terrestrial, arboreal (tree-dwelling), semi-aquatic, and aquatic species; one group is entirely marine; many are poisonous. They have no external ear openings, eardrums or middle ears; sound vibrations are detected through the ground. Their eyelids are immovable and their eyes covered by a transparent protective cover. The long, forked, protractile tongue is used to detect odours. Their bodies are covered with scales. Poisonous snakes have hollow or grooved fangs, through which they inject venom into their prey. See individual species

snake / snāk/ • n. 1. a long limbless reptile (suborder Ophidia or Serpentes) that has no eyelids, and jaws that are capable of considerable extension. Some snakes have a venomous bite. ∎  (in general use) a limbless lizard or amphibian. 2. (also snake in the grass) a treacherous or deceitful person. 3. (in full plumber's snake) a long flexible wire for clearing obstacles in pipes. • v. [ intr.] move or extend with the twisting motion of a snake: a rope snaked down. DERIVATIVES: snake·like / -ˌlīk/ adj.

374. Snakes

See also 16. ANIMALS ; 353. REPTILES .

ophidiophobia

1. an abnormal fear of snakes. Also ophiophobia .

2. herpetophobia.

ophiography

a description of snakes. —ophiographic, adj.

ophiolatry

the worship of snakes. — ophiolater, n.

ophiology

the branch of herpetology that studies snakes. Also called snakeology, snakology. —ophiologist, n. —ophiologic, ophiological, adj.

ophiomancy

a form of divination involving snakes.

snakeology, snakology

ophiology.

snakes Common in Palestine, and often mentioned in the Bible from Gen. 3: 14 onwards. There existed cobras and vipers. In Malta Paul is said to have been bitten by a snake (Acts 28: 3). Not surprisingly, snakes feature also as symbols of evil (Ps. 58: 4) and the Devil is called ‘that old serpent’ (Rev. 20: 2.). Nevertheless snakes are credited with an enviable wisdom (Matt. 10: 16).

Snake

a term applied to things or a formation resembling a snake—Wilkes.

Examples : a black snake of men winding across the plain, 1891; snakes of ribbon, 1894.

snake OE. snaca = MLG. snake, ON. snákr, snókr; rel. to OHG. snahhan crawl, and further to Ir. snaighim I crawl.

Snake, a character in Sheridan's The School for Scandal.

SNAKES

SNAKES. SeeHerpetology .

snakes See SERPENTES.

snakes See Squamata.

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