Fig. 4.65 Echis carinatus in threatening pose. The coils of the body are in constant motion.

Distribution

From West, East and North Africa across the Middle East to India and Sri Lanka. See also link "Distribution" at the top of the page for detailed information.

  Map 47 Echis spp. (E. hughesi, E. jogeri, E. khosatzkii, E. megalocephalus and E. omanensis not shown)
  Echis leucogaster
  E. pyramidium
  E. multisquamatus (=E. carinatus multisquamatus)
  E. ocellatus
  E. coloratus

  E. carinatus

 
Distribution areas of those subspecies that are not shown in the Distribution tables:

-Echis carinatus carinatus: Central and southern India

-Echis carinatus astolae: Astola Island (southern Pakistan)

-Echis carinatus sinhaleyus: Northern and eastern Sri Lanka

-Echis carinatus sochureki: Northern India, Pakistan, southeast Afghanistan, southern Iran, United Arab Emirates and northeast Oman

-Echis pyramidum pyramidum: Northeast Algeria, Tunisia, northwest Libya, Egypt, Sudan, Ethiopia, northern and southwest Somalia, northern Kenya, southwest Saudi Arabia, Yemen, southern Oman

-Echis pyramidum aliaborri: Northeast Kenya

-Echis pyramidum leakeyi: Western Kenya

Biology

With an average length of 35 cm, some rare specimens up to just over 80 cm, the physical size of carpet vipers is by no means commensurate with their huge medical significance. E. carinatus in the old taxonomic sense, with its vast area of distribution from west Africa to India and Sri Lanka, is said to claim more human lives worldwide than any other species of snake.

The body structure is relatively slender for viperids. The head is distinct from the body and is oval-shaped, with a blunt snout and eyes set well forward. The head of E. coloratus is more pear-shaped, with protruding "cheeks". Distinctly carinate scales. The rows of scales on the sides of the body stick out at a conspicuous angle and have a serrated keel (hence the name "saw scaled viper"). These side scales produce a typical, clear warning sound when the snake rubs the coils of its body together. The sound is similar to that made when two pieces of sandpaper are rubbed together.

Basic colouring from greyish to sand-coloured and brownish shades. Red elements also possible in E. ocellatus and E. coloratus. Row of white blotches or bars along the spine, sometimes with dark edges. These may be partly or wholly separated along the line of the backbone and pushed together. Light wavy bands along the sides (not in E. coloratus and E. ocellatus). Instead of these wavy bands, E. ocellatus has a distinct row of darker blotches with white edges ("ocelli").

The belly is light-coloured, in E. ocellatus always with dark speckles. These speckles are never seen in E. leucogaster; in the other species they are sometimes present. Except for E. coloratus, the Asian species have a light head marking in the form of a cross or an arrowhead; in E. pyramidum it is more in the form of a Y. E. coloratus has 3–4 rows of small scales between the eyes and the shields of the upper lip; the other species generally have 2 rows (rarely 1 or 3).

Typical inhabitants of dry regions, such as sand deserts, semi-arid rocky deserts, steppes and savannas, but also in agricultural areas and gardens. E. carinatus sochureki and E. multisquamatus up to an altitude of 2,000 m.

The population density of these snakes can be tremendously high in some areas. In Ratangiri, India, in a culling operation at the end of the 19th century, over 115,000 Echis specimens were collected! In northern Kenya, 10 people collected around 7,000 snakes over a period of just a few months.

Carpet vipers are mainly active at night, but also during the day in cool weather, and otherwise hide themselves under stones, bushes or fallen branches. Side-winding, a mode of locomotion often used by desert-dwelling snakes, can also be observed in Echis species (especially on sandy or smooth terrain). During side-winding, the upper body is thrown forwards. The head is then braced and the remaining coils are pulled along without touching the ground. This form of locomotion is at an angle to the longitudinal axis of the snake's body and leaves behind unconnected, parallel tracks on the sand.

When threatened, carpet vipers become extremely nervous and agitated and rarely flee. The body is coiled, and the coils are rubbed against each other constantly to produce a warning sound. The head is kept still and directed towards the cause of the disturbance. From this position, they dart forwards repeatedly and rapidly with impressive force in order to strike. The harmless African egg-eating snakes (Dasypeltis spp.) display similar warning behaviour.

Risk

Envenoming must be treated very seriously and often takes a serious course. Because of the great variation in venom composition, it is crucial for treatment of an E. carinatus bite, in particular in order to choose the correct antivenom, that the geographical origin of the animal is known.  

Although these animals are relatively small, they possess extremely potent venoms in sufficient quantities to cause severe and lethal envenoming. Their extremely high prevalence in certain areas and their readiness to bite immediately make Echis spp. a serious threat to the rural population in some areas.

In terms of morbidity and mortality, carpet vipers are considered the most important venomous snakes in the world (Warrell and Arnett 1976). Research in the savanna region of Nigeria clearly shows that the medical significance of Echis was underestimated there. E. ocellatus causes more cases of envenoming in that region than all other venomous snakes together. At times up to more than 10% of hospital beds are occupied by patients with Echis bites (Pugh and Theakston 1987a, Warrell et al. 1977). In the Benue valley in Nigeria, the annual snakebite incidence has been calculated to be 602 per 100,000 inhabitants, with a mortality of 12.3%. E. ocellatus is responsible for an overwhelming proportion of these bites (Pugh and Theakston 1980).

The significance of other Echis species seems to be smaller. None of the 21 observed cases of E. pyramidum bites in Sudan ended fatally (Corkill 1956).

In India, the expected mortality rate from E. carinatus bites is 10–20%, although the significance of all Echis bites together is lower than those of cobras, kraits and Russell's viper (Murthy 1990). In Kashmir, E. carinatus sochureki is a frequent cause of severe systemic envenoming (Bhat 1974).

E. coloratus and E. carinatus sinhaleyus are considered less dangerous than their relatives, and bites are less common (Kochva 1990, Mendelssohn 1965, M'Disi 1990, De Silva 1990).

Bites are frequent in Pakistan, but seldom fatal (Khan 1990).

Literature (biological)

Baboscay 2004, Cherlin 1983, 1990, Daniel 1983, Deoras 1971, 1978, Disi 1990, Gasperetti 1988, Hughes 1976a, Latifi 1991, Mallow et al. 2003, Mendelsohn 1965, Pitman 1974, Roman 1972, 1980, Stemmler 1969a, b, 1970, Stümpel and Joger 2009, Trape 2018, Villiers 1975, Warrell and Arnett 1976