West African carpet viper

Identification

The West African carpet viper is a small, fairly slender viper with overlapping, keeled scales; the scales on its flanks have serrated keels³. It is reddish-brown or greyish, with pale oval or diamond-shaped marks along the back joined by a dark central band, and a row of white, black-edged “eye” spots along each side³. The belly is white and heavily spotted with black³. Its scientific name comes from the Latin ocellus, “little eye”, after these spots¹.

Adults are usually 30–50 cm long (about 40 cm on average), and the maximum recorded length is about 70 cm³.

Distribution

This viper lives in the savanna of West Africa³. The Reptile Database lists it from Senegal, the Gambia, Guinea, Mali, Mauritania, Burkina Faso, Côte d’Ivoire, Ghana, Togo, Benin, Niger and Nigeria¹.

WHO’s 2010 guidelines, written before a recent split, extended its range east to Chad, Cameroon and the Central African Republic³. In 2018 the carpet vipers of that region were described as a separate species, Echis romani, which the Reptile Database also lists from parts of Nigeria and southern Niger^1,2.

Habitat

The West African carpet viper is a savanna snake³. The West African savanna has the highest snakebite incidence in Africa, and saw-scaled or carpet vipers are among the commonest causes of serious envenoming there³. In the Sudan savanna around Ouagadougou, Burkina Faso, people meet it in and around their homes, sometimes indoors⁴. In Nigeria, snakebite is a major public health problem among farming communities of the savanna⁵.

Behaviour

Around Ouagadougou, carpet viper bites happen mostly at night, including dusk and dawn, and mainly at the beginning and end of the rainy season⁴.

When alarmed, a carpet viper rubs its coils together so that the saw-edged keels on its side scales make a rasping sound³. This sound is easy to recognise and is the source of many local names, such as kububuwa in Hausa and fufukr in Bura³.

Diet

In a study of 47 carpet vipers collected around Ouagadougou, 39 had food remains in their gut⁴. The commonest prey were large Scolopendra centipedes, found in 19 snakes, followed by rodents, found in 12⁴. Other remains included three snakes, a toad, a spider, a beetle and some ants⁴. The author suggested that hunting centipedes, which are common around homes, may help explain why people often meet these vipers near houses at night⁴.

Reproduction

The West African carpet viper lays eggs¹. In this it differs from the saw-scaled viper of South Asia (Echis carinatus), which gives birth to live young; the Reptile Database notes that the other species of the genus lay eggs⁸.

Venom and medical significance

The West African carpet viper is the most important cause of snakebite in West Africa, and in Nigeria it has been reported to cause about 90% of snakebites and 60% of snakebite deaths³. It is also the most common cause of snakebite deaths in Senegal¹, and in Nigeria more than 10–20% of envenomed patients die if untreated⁶.

Its venom activates clotting factors, so the blood stops clotting³. In a large Nigerian series only 4% of proven bites caused no envenoming; all envenomed patients had non-clotting blood, more than half had spontaneous bleeding, usually from the gums, and some developed blistering or tissue death that needed skin grafts or amputation³. Antivenoms made from Nigerian snake venoms, EchiTAb G and EchiTAb-Plus-ICP, proved effective in a large trial, and antivenom prevents more than 80% of deaths from carpet viper bites^5,6. Anyone bitten should go to hospital immediately.

Conservation

The West African carpet viper is listed as Least Concern on the IUCN Red List (assessed in 2021)⁷. It remains common in the West African savanna, where it is still a leading cause of snakebite^3,5.

Similar species

Other carpet vipers in West Africa look much the same. Joger’s carpet viper (Echis jogeri) of Mali and Senegal has similar colouring and differs mainly in its belly scale counts, while the white-bellied carpet viper (E. leucogaster) has a pure white belly rather than one spotted with black³. Echis romani, east of its range, differs in genetics and scale counts².

It also looks like the saw-scaled viper (Echis carinatus), but that species lives far away, from Arabia and Central Asia to India and Sri Lanka⁸. These differences are not a safe basis for handling any snake. Keep your distance from every snake you cannot identify.

In captivity

The West African carpet viper is dangerously venomous and is not suitable as a pet. Captive carpet vipers are kept for medical research: the starting doses of Nigeria’s antivenoms were worked out from the largest amount of venom that could be milked from captive snakes⁶.