The vipers

The viperid family brings together, as its name suggests, the vipers (in the broad sense) and contains 227 species.

Most vipers are short and stocky, with a broad, triangular head and keeled scales, although there are exceptions in each case. This family is considered the most evolved of all snakes, with many features found in no other family (solenoglyphous fangs, with which they envenomate their prey, and, in the rattlesnakes, heat-sensitive pits on the face).

Viperids are found across much of the world, but are absent from Australasia and Madagascar. Several adaptations allow them to live in cold places, and this family includes the northernmost snake (the common adder, or northern viper) and the southernmost (the hognose lancehead), as well as the snake that lives at the highest altitude, at 4900 m, in the Himalayas (the Himalayan pit viper, or Himalayan moccasin).

There are 4 subfamilies, all well defined:

• the Azemiopinae: they contain a single species, Fea's viper, considered the most primitive viper. It is one of the rarest vipers; it is found in Burma and China.
• the Causinae: they comprise 6 species of small, slender vipers, the night adders, all native to Africa, which look more like colubrids than most other vipers.
• the Viperinae: the 66 species of this subfamily are for the most part stout snakes of small to medium size, among which are the famous Gaboon viper, the saw-scaled viper and the northern viper. They are found in Europe, Africa and Asia
• the Crotalinae: they contain 154 species, including the famous rattlesnakes, and are found on the American continent, in Africa and in Asia.

The puff adder:

It is a large viper (about 1 m) that moves slowly. It lives in the bush, savannahs, mountain slopes and semi-desert regions. In Africa it is responsible for a large number of bites; yet it is not aggressive, but it is so well camouflaged that one can easily step on it without seeing it. It bites quickly and its long fangs sink in deeply. Death can generally be avoided if treatment is given promptly. When disturbed, it puffs itself up with air, which it then releases while producing a loud, deep and intimidating hiss, or a drawn-out 'sssssch', hence its other name of common puff adder.

The Gaboon viper:

It is a much-feared snake, although bites are rare. It lurks among dead leaves, very well camouflaged by the geometric, rectangular and triangular patterns of its body. It hardly moves, preferring to wait for prey to come within reach before biting it in a flash and injecting its venom with fangs that can reach 5 cm!

Its size is impressive (it can reach 2 m!), as is the thickness of its body and the width of its triangular head, due to the very large venom glands located below and behind each eye. It too can inflate its body to appear even larger, and emit a loud, high-pitched hiss as it breathes out.

The saw-scaled viper (Echis carinatus):

Although small (just over 50 cm), it is very dangerous, because of its venom and its tendency to bite when disturbed (it can bite vigorously and repeatedly). It is responsible for most human deaths from snakebites throughout its range (the Middle East), owing to its abundance and its habit of partly burying itself in the ground. There it lies in wait for prey, remaining motionless and almost invisible. It lives in semi-desert areas, dry grasslands and rocky places.

This species is more slender than its related vipers and has a very characteristic pear-shaped head with a rounded snout. All saw-scaled vipers adopt the same defensive posture: they coil their body into a horseshoe shape, so that the specialised scales (which have a serrated keel) of one section of the flanks lie close to those of another section, but oriented in the opposite direction. When the snake's coils move, the keels rub against one another and produce a shrill rasping sound.

The Texas rattlesnake:

It is also called the western diamondback rattlesnake. It is a large, stout snake (about 1.30 m) whose colour varies to blend in with the ground. It is found in North America, in deserts, scrublands and rocky hillsides. Its tail is ringed with black and white, just before the rattle. The rattle can have up to 10 segments and serves to produce a warning signal against any potential threat. It also stops large mammals from accidentally trampling the snake. A new segment is added to the rattle each time the rattlesnake sheds its skin.

In the United States, a few states still permit rattlesnake hunting, and the Texas rattlesnake is the species that suffers most from it. Large numbers of snakes are killed for the entertainment of spectators. Some local populations of this rattlesnake have been almost wiped out.

The white-lipped bamboo pit viper:

This snake, about 1 m long, is adapted to the arboreal life of humid tropical forests and only very rarely comes down to the ground. It lives in China, India and the Indonesian archipelago. It is mainly nocturnal and normally hunts by ambush, holding the front of its body curved into an S shape, ready to bite prey passing within reach. It can remain like this for several minutes, or even hours. Although it is venomous and easily provoked, human deaths from its bites are rare, because its venom is weak.

Arboreal pit vipers are more slender and agile than their related terrestrial species, often have large eyes and are most often green in colour, which gives them excellent camouflage.

Keeping and precautions

Viperids (vipers, rattlesnakes, etc.) have a venom that acts mainly on the blood and tissues: it can cause bleeding, significant swelling and local damage. Keeping them is by no means trivial and is a matter for licensed and trained keepers.