What are the characteristics, habitats, breeding, enemies, feeding habits of viper snakes? Information on viper sanke and viper bite.
Viper Snake; reptiles of the family Viperidae, which includes many dangerously venomous snakes inhabiting Europe, Asia, and Africa. Vipers have tubular fangs that are tilted back against the roof of the mouth when not in use. The venom apparatus is essentially the same as that of the rattlesnake and other pit vipers, which are not true vipers.
The fangs of both vipers and pit vipers are proportionately longer than those of cobras and their allies in the family Elapidae, in which the fangs are permanently erect at the front of the jaw. While such primitive vipers as the African night adders (Causus) have relatively short fangs, those of the big vipers are comparatively enormous. The Gaboon viper (Bitis gabonica), at its maximum length of approximately six feet, has the largest fangs known, nearly two inches in length if measured along the curve. The venom apparatus serves primarily as a means of killing or subduing the prey, and secondarily as a means of defense.
In older classifications snakes equipped with the fang-tilting mechanism characteristic of vipers and pit vipers were placed in the suborder Solenoglypha as a subdivision of the order that includes all snakes. At present the vipers and pit vipers are placed in separate families, or sometimes in subfamilies (Viperinae and Crot-alinae, respectively) of the family Viperidae. The presence on each side of the head of a pit located behind and below the nostril distinguishes the crotalids or pit vipers from the viperids, or true vipers, which lack the heat receptors contained in the pair of pits.
Form and Coloration.—With few exceptions vipers are rather heavy bodied. The head is commonly broad, and sharply set off from the body in most species, but the night adders and especially the burrowing vipers (Atractaspis) are relatively slender, with narrow heads. Along with the rare Fea’s viper (Azemiops feae) of Upper Burma and the adjacent parts of China and Tibet, they retain enlarged plates instead of having small scales on the top of the head, as is characteristic of most vipers.
Vipers vary from the uniform black or lead color of burrowing forms, through the pale gray or buff typical of the desert dwellers, to the complex symmetrical patterns of yellowish brown, purple, and reddish colors seen in such forest-dwelling forms as the Gaboon viper. Most arboreal vipers (Athens) are green, rarely yellow, often with ill-defined darker markings.
Distribution.—The true vipers are represented in Europe by one genus containing 8 species, and in Asia by 5 genera that include 14 species. In Africa, the center of their abundance, there are approximately 40 species belonging to 7 genera.
Habitats.—The principle of adaptive radiation is exemplified by the vipers in Africa, where those in one genus (Athens) have prehensile tails and are largely arboreal, living either in trees or shrubs. A second group, comprising species of the genera Bitis, Causus, Echis, Aspis, and Vipera, are primarily terrestrial, though the Sahara horned viper (Aspis cerastes) buries itself in the sand. There are no truly aquatic species, but the rhinoceros viper (Bitis nasicornis) frequents swamps or moist forest habitats. Burrowing vipers, (Atractaspis), found only in Africa and the adjacent portions of Asia Minor, are the only vipers that move beneath the soil; they rarely appear on the surface except after rains.
Terrestrial vipers are widely distributed in Europe and Asia. The adder (Vipera berus and its subspecies) inhabits an extensive range, from the British Isles (except Ireland) eastward across Europe and Asia to Sakhalin Island on the Pacific coast, including areas within the Arctic Circle, north of the Baltic Sea. In Africa, vipers occur as far south as the Cape of Good Hope.
Breeding.—All vipers give birth to living young, with the exception of the night adders (Causus) and the burrowing forms (Atractaspis), which lay their eggs in the ground, or in decaying vegetation. Some large vipers are extremely prolific. The widely distributed puff adder (Bitis arietans) of Africa and the Arabian Peninsula may produce 70 young at a time, and 63 are reported in a single litter produced by Russell’s viper (also known as the “daboia” and “tic-polonga”) in Asia. In contrast, the smaller night adder (Causus rhombeatus) seldom lays more than 20 eggs, and the secretive burrowing viper may lay only one egg at a time.
Vipers use their sense of smell in finding mates. Rival males indulge in a spectacular performance called the “dance of the adders.” With the head and the fore part of the body held erect, competing males face each other as each endeavors to push his opponent to the ground. This “dance” sometimes continues for hours, accompanied by elaborate swaying movements, until one male or the other is momentarily forced over on his back. There is no biting in such contests, which may be interpreted as a manifestation of territoriality, or in some instances as males competing for mating rights. Similar behavior in American pit vipers was mistakenly interpreted as a “courtship dance.”
Vipers commonly produce a brood every year, but in northern Europe, and at higher elevations in the Alps, gestation in the adder (Vipera berus) requires two growing seasons. Thus under such extreme conditions a brood is produced only on alternate years by these vipers.
Size.—Vipers range in size from slender bur-rowers scarcely a foot long to the maximum length encountered in Russell’s viper, which may exceed six feet. Other vipers attain dimensions between these extremes, ranging in size from two to three feet. Arboreal vipers, and those dwelling in regions with short growing seasons or in sandy deserts, tend to be smaller. Males often attain larger dimensions than females.
Feeding Habits.—Most vipers prey on the smaller mammals, principally rodents, but night adders feed upon toads, and burrowing vipers occasionally devour blind snakes (Typhlops). The common adder eats field mice, voles, shrews, the eggs and nestlings of birds, as well as lizards, frogs, and salamanders. Juvenile vipers select such small prey as insects, slugs, and worms.
Enemies.—The principal enemy of vipers is undoubtedly man. In addition to destroying or disturbing natural habitats, human beings, because of their fear of being bitten, kill great numbers of vipers. Predatory birds, hedgehogs, foxes, badgers, other snakes, and even fishes devour vipers. They are subject to infestations of mites and ticks, and commonly harbor internal parasites.
Viper Bite.—There are few reliable statistics concerning the incidence of snakebite. Some 20,000 to 25,000 deaths from venomous snakes are said to occur annually in India. In Europe, where vipers are the only dangerous snakes, fewer than 20 deaths from snakebite are reported annually. In Africa, bites of the burrowing vipers, the saw-scaled vipers (Echis), and the puff adder (Bitis arietans) and its allies, are probably responsible for more human fatalities than bites from mambas, cobras, and other venomous snakes.
The venoms of vipers differ from species to species. Many venoms contain a powerful depressant that may cause death from cardiac failure when sufficiently large amounts reach the bloodstream of the victim. Other elements in the venom affect the central nervous system. Vipers normally kill small animals within minutes or even seconds, but large animals seldom succumb unless the viper manages to inject a large amount of venom when biting the victim.
Symptoms of viper bite in human beings are usually extreme pain and swelling, with discoloration at the site of the penetration. Neurotoxic elements in the venom may cause vomiting, diarrhea, or prostration, sometimes with the loss of consciousness. In fatal cases the pulse and respiration weaken gradually until death ensues, usually five or six hours after a bite, though in rare instances it may be delayed until the third day. Victims surviving for longer periods usually recover.