1911 Encyclopædia Britannica/Viper

VIPER. The vipers constitute a family of Old-World poisonous snakes, with a pair of poisonous fangs in the maxillary bones, which are short and movable. The main anatomical features are described in the article Snakes. In the present article only the Viperinae, namely those without an external pit between the eye and the nose, are described. Pit vipers, or Crotalinae, are treated under Snakes, and those which are possessed of a rattle under Rattlesnake. The true vipers comprise about nine genera with some forty species, which can be distinguished as follows:—

Causus in Africa, and Azemiophis feae in Burma, are the only vipers which have the head covered with large symmetrical shields, while in the other genera the head shields are broken up into small shields, or into still more numerous scales. C. rhombeatus, common from the Gambia to the Cape.

Atractaspis, small burrowing snakes in Africa, without post-frontal bones.

Echis and Atheris have only one row of subcaudal shields. E. carinata, scarcely exceeding 20 in. in length, is very poisonous and easily overlooked on account of its light brown coloration, with pale spots and delicate markings on the keels of the scales of the back. It is a desert type, having the lateral scales strongly keeled and directed downwards, by means of which it shuffles itself into the sand; by folding itself and rubbing the scales together it produces a rustling sound. It ranges from India, where it is known as the "Krait" called "Kuppur" in Sind, through North Africa. This desert type is replaced farther south in Africa, where vegetation flourishes, by the closely allied genus, Atheris, which, however, possesses a prehensile tail and vivid coloration and has assumed truly arboreal habits.}}

Fig. 1.—Echis carinata. The "Krait" of India.

Cerastes is another desert form, but is restricted to Africa; the arrangement of the scales of the sides of the body is similar to that of}} Echis, but it has two rows of subcaudals. C. cornutus, the "horned viper" of North Africa, from Algeria to Palestine, has a large horny spike above each eye. This, the "Efa" of the Arabs, buries itself in the sand, with only the eyes, nostrils and the horns appearing above the surface. It attains a length of 21/2 ft. C. vipera is hornless.
Fig. 2.—Atheris burtoni. (Length, 12 in.)
Bitis s. Echidna s. Clotho has two rows of shields on the underside of the very short tail; the thick head is much depressed, like the body. The nasal shields are separated from the rostral by small scales, otherwise much resembling the genus Vipera. B. arietans, the “puff-adder” of nearly the whole of Africa, an ugly, very dangerous brute growing to a length of 4 or 5 ft. B. nasicornis, the West African nose-horned viper, has a pair of erectile scales on the nose. Scarcely smaller and less bulky than the puff-adder and just as poisonous, it is yet very handsomely marked with a series of large pale, dark-edged spots and oblique crosses on a purplish or reddish brown ground. Especially handsome are the young, which at birth are as much as 1 ft. in length. On one occasion one of these snakes, after giving birth to twenty-one young (which bit and killed mice within five minutes of being born), became very ill-tempered, and when two adult males were placed in her cage she bit one with such violence as to break off one of her fangs, which she left, about three-quarters of an inch in length, sticking in his back. He, however, appeared not to suffer the slightest inconvenience, and was never the worse for it (see Proc. Zool. Soc. 1871, p. 638).
Fig. 3.—Bitis nasicornis. (Length, 12 in.)

Vipera.—The head is covered with small scales and a few larger shields. The eye is separated from the labials by small scales; the nasals are in contact with the rostral shield or separated by one naso-rostral. The scales of the body are strongly keeled; two rows of subcaudals on the short tail. This genus of about ten species with numerous local varieties ranges over Europe, Asia and the greater part of Africa.

V. berus, the common European viper, ranging from Wales to Saghalien Island and from Caithness to the north of Spain, from the northern boundary of Persia to beyond the Arctic circle in Scandinavia. It inhabits all sorts of situations, but prefers heaths, moors and mixed woods with sunny slopes. It ascends the Alps up to 6000 or 7000 ft. The coloration is very variable, grey, brown, reddish or entirely black specimens occurring in the same country. The much-spoken-of black zigzag line along the back is so often indistinct, that it cannot be relied upon as a safe character. The full-grown males are smaller than the females, and have usually darker markings and a lighter ground colour. A specimen which is 2 ft. long is rare, and is invariably a female. The chief food is mice which are hunted after sunset. They cannot climb and they avoid going into water. The pairing takes place from March to May and the young are born about four months later. During the pairing, and for hibernation, they often collect in considerable numbers. Whilst most snakes readily take proper food in captivity, these vipers prefer starving themselves to death, a feat which they accomplish within six to nine months according to conditions. As a rule their bite is not fatal to man, but the consequences are often serious and protracted. For treatment see Snakes.

V. aspis is the more southern and western continental European viper; it is slightly snub-nosed, and this feature is still more pronounced in V. latastei of Spain and Portugal. In V. ammodytes of south-eastern Europe the raised portion is produced into a soft, scaly appendage.

V. russelli, the "Daboia" is one of the most poisonous snakes of India, Ceylon, Java, Burma and Siam. It is pale brown with three longitudinal series of black, light-edged rings which sometimes encircle reddish spots. It grows to a length of about 5 ft.

 (H. F. G.)