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Bothrops atrox

Common names: common lancehead, fer-de-lance, barba amarilla.

Bothrops atrox is a venomous pitviper species found in the tropical lowlands of northern South America east of the Andes. No subspecies are currently recognized. This species is very dangerous and is the cause of more human fatalities than any other American reptile.


A terrestrial species, adults usually grow to total length 75125 cm and are moderately heavy-bodied. Reports of the maximum size are not clear, as this species is often confused with B. asper. Soini (1974) mentioned that of a series of 80 specimens collected in northeastern Peru, the largest was a female of 138.8 cm. The largest specimen measured by Campbell and Lamar (2004) was a female with a total length of 162 cm.

The scalation includes 23-29 (usually 23-25) rows of dorsal scales at midbody, 169-214/177-214 ventral scales in males/females, 52-86 (usually 75 or fewer) subcaudal scales in males, which are usually divided, and 47-72 subcaudals in females. On the head the rostral scale is about as high, or slightly higher, than it is wide. There are 3-11 (usually 5-9) keeled intersupraocular scales, 7-13 (usually 8-11) sublabial scales and 6-9 (usually 7) supralabial scales, the second of which is fused with the prelacunal to form a lacunolabial.

The color pattern is highly variable, including a ground color that may be olive, brown, tan, gray, yellow, or (rarely) rusty. The body markings are highly variable, as is the degree of contrast: in some specimens the pattern is very well defined, while in others it may be virtually absent. In general, however, the body pattern consists of a series of dorsolateral blotches that are rectangular or trapezoidal in shape and extend from the first scale row to the middle of the back. These blotches may oppose or alternate across the midline, often fusing to form bands. They also have pale borders, which in some cases may be prominent, and may be invaded from below by tan or gray pigment, occasionally dividing them into pairs of ventrolateral spots. The belly may be white, cream or yellowish gray, with an increasing amount of gray to black mottling posteriorly that may fade again under the tail. The head usually does not have any markings other than a moderately wide postocular stripe that runs from behind the eye back to the angle of the mouth. The iris is gold or bronze, with varying amount of black reticulation, while the tongue is black.

Common names

Common lancehead, fer-de-lance, barba amarilla.

The Spanish common name barba amarilla (yellow beard), an allusion to the pale yellow chin color, is also used in English. In Guyana it is called labaria or labarria. In Peru it is called aroani (Yagua), cascabel (juveniles), ihdoni (Bora), jergon, jergona, jergon de la selva, macanchi (Alto Maranon), machacu, marashar and nashipkit (Aguaruna names). In Venezuela it is called mapanare. In Colombia it is known as mapana (Llanos of Vichada) and taya equis, in Peru as jergon. The latter is an allusion to the x-like markings of the color pattern. In Ecuador these x-like markings have led to the snake simply being referred to as equis (the Spanish pronunciation of the letter 'x'). In Trinidad it is known as mapepire balsain.Cote ce Cote la: Trinidad & Tobago Dictionary, p. 75. John Mendes. (1986) Arima, Trinidad.

Geographic range

Found in the tropical lowlands of South America east of the Andes, including southeastern Colombia, southern and eastern Venezuela, Guyana, Suriname, French Guiana, eastern Ecuador, eastern Peru, northern Bolivia and the northern half of Brazil. The type locality is listed as "Asia", which is obviously a mistake. Schmidt and Walker proposed that this be corrected to "Surinam."


Despite the vast destruction of rain forests, it is amongst the most numerous of pit vipers and is not endangered. In Trinidad it prefers wet lowland forests.


Although generally terrestrial, it is also an excellent swimmer and even climb trees when necessary to reach prey. Generally nocturnal, but may forage at any time of the day if necessary. These snakes are also very easily agitated and strike quite often.


The main diet includes most small mammals and birds, but also frogs and lizards. Larger prey is struck and released, after which it is tracked down via its scent trail.


Breeds year-round. After mating, females with developing embryos travel in and out of sunlight to keep them at a constant temperature. In equatorial regions, the gestation period is approximately 34 months, with an average of 60 young per litter. At birth the young are about 30 cm in length, more brightly colored than adults, and have yellow or beige tails.


These snakes are known to search for rodents in coffee and banana plantations. Workers there are often bitten by the snakes, which can lie camouflaged for hours, nearly undetectable, and striking with high speed.

They are much feared because their venom is a hemotoxin that is particularly lethal and fast-acting. The fatality rate used to be high, but nowadays treatment is usually possible if the victim receives medical attention soon enough. Venom yield averages 124 mg, although it may be as much as 342 mg. The fatal dose in humans is just 62 mg.

Commonly, bites from this snake to humans cause symptoms including nausea, blackouts, and paralysis. In almost all cases, temporary or sometimes permanent loss of local or 'short term' memory were reported. Extended hospital stays, as well as weight loss of up to fifteen pounds have been reported.

The enzyme, reptilase (batroxobin), derived from this snake's venom is used in modern medical laboratories to measure fibrinogen levels and to measure blood coagulation capability. The test is considered to be a replacement for Thrombin Time, and is used when heparin is present in the sample. The enzyme is unaffected by heparin.


The taxonomy of this species is controversial; it may include the B. leucurus and the B. moojeni, and some of its populations are sometimes said to be separate species. B. asper was formerly included in this species, but most authorities now consider it distinct.

See also

List of crotaline species and subspecies


Further reading

Hays WST, Conant Sheila. 2007. Biology and Impacts of Pacific Island Invasive Species. 1. A Worldwide Review of Effects of the Small Indian Mongoose, Herpestes javanicus Pacific Science - Volume 61, Number 1, pp. 316.

Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. ISBN 0-8069-6460-X.

O'Shea M. 2005. Venomous Snakes of the World. ISBN 0-691-12436-1.

External links

Animal Diversity Web page on the common lancehead

Page on the common lancehead in Manaus, Brazil, with links to photographs (in Portuguese).

. Accessed 14 January 2007.

. Accessed 5 December 2007.

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This article is licensed under the GNU Free Documentation License. It uses material from the Wikipedia article Bothrops atrox

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