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Bothrops Atrox, Commonly Called Labaria or Fer de Lance

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Published: 31st of August, 2023 by Patrick Carpen

Last updated: April 13, 2024 at 20:46 pm

The reptile which goes by the scientific name Bothrops Atrox is known in Guyana s the labaria snake. It is also variably called fer-de-lance, lancehead, and barba amarillia. In Venezuela, it is called mapanare. In Trinidad, it is called mapepire balsain and in Brazil it is known as jararaca.

Kingdom: Animalia
Phylum: Chordata
Class:    Reptilia
Order:   Squamata
Suborder: Serpentes
Family:  Viperidae
Genus:  Bothrops
Species: B. atrox

Watch: Labaria Snake Crossing Road in Leguan, Guyana, South America

Video by Royan Alleyne

The labaria (Bothrops atrox) may be identified by having the following combination of features: a triangular-shaped head with a snout that is not upturned, low keels (longitudinal ridges) on the dorsal scales, heat-sensing pits between the eyes and nostrils, and a faint dorsal pattern of 20–33 pale X-shaped markings on a brownish dorsum.  Newly-hatched lanceheads have brightly-colored tail tips (yellowish in males and whitish in females).


One of the most widespread snakes, found in Trinidad and also the tropical regions
throughout South and Central America (Boos, 2014). Found in habitats such as tropical coniferous and tropical dry forests, tropical evergreen forests and rainforests – although it can be found invading plantations or agricultural areas (proximity to prey).

Banana plantations are particularly liked by this species because of their rats. They like to live close to stream edges and in ditches. However, they can thrive in any habitat. The labaria can be found sleeping, camouflaged under leaves during the day, but they hunt actively at night.

The bothrops atrox is considered a lowland species that can be found from sea level to 1300 m in altitude in Central America. In Venezuela though it has been found at considerably higher elevations – up to 2500 m – and even at least 2640 m in Colombia.


Solitary, nocturnal, territorial. Little information has been published on its social organization. Its home range averages between 3.7 and 5.9 hectares, which is considered small in relation to other pit-vipers.


Mainly nocturnal, the labaria snake sleeps for the majority of the day. At night, it will feed primarily on agricultural pests. It spends its days among leaf litter or concealed in roots, or in similar locations.
In captivity, fer-de-lance has a reputation for being unpredictable and psychotic; so much so that it is recommended that only experienced keepers maintain this species. Most of the time they sit motionless but once physical contact occurs it explodes into action (Sierra, 2003). Unlike many other vipers, there has been no documented cases of male to male combat among the labarias.


The labaria snake is a carnivorous predator and hunter which relies on camouflage to attack prey. It deduces the position of its prey by using its pit organs (relays thermal information of the prey’s position to the snake) located between the eye and nostril. The snake is very intrusive by nature, and conflicts with humans occur due to its habit of invading plantations in search of prey and laying in walking trails.

Diet for adults consists of small mammals such as rodents and opossums, but they take birds occasionally depending on the snakes’ size. They have also been found to eat lizards and smaller snakes. Juveniles prey on frogs, lizards, small vertebrates and arthropods (Carnley, 1996).

When about to strike, Fer-de-lance gears up forming an ‘S’ shape with its head and upper body – and is capable of striking so quickly that it is almost impossible to see it move from this position. When striking, it instantaneously injects a lethal dose of poison after which it retreats and waits for it to work. When the prey is dead, B. atrox locates it by pursuing its scent trail, and then leisurely eats its prey.

A tactic commonly used by B. atrox is when striking it passes its head past the victim and doubles back while spiraling its neck quickly, so catching its prey from behind. Dean Ripa says, “By my estimation, the world’s most dangerous viper to catch.”

Its venom is very poisonous – on average 105mg of venom is injected into one bite, but up to 310mg have been recorded when milking fer-de-lance. For humans, the fatal dose is 50mg. UWI The Online Guide to the Animals of Trinidad and Tobago.


Communication and perception is not well studied in fer-de-lance. They have heat-sensing pits (used at night to detect prey) which are seen as two indentations located behind and above the nostrils through which they use to “identify a rise or drop in temperature of just 0.001 degrees Celsius” (Phelps, 1981). This mechanism grants it to recognize warm-blooded mammals. Coupled with this is its chemical communication, through which they use their tongues to ‘taste’ the air; as seen in Fig. 4. They perceive their environment through visual, infrared, tactile, and chemical stimuli.


Viviparous (giving birth to live young), iteroparous (breeding repeatedly). Females build up fat stores which leads to a release in hormones that stimulate ovulation. Mating begins with the male making a series of movements, after which he gradually follows the female who then stops moving, allows him to approach while she assumes position. Male tends to bob his head at her side. Fer-de-lance reaches sexual maturity at around 1.5 years. They are live-bearing and breed annually. They breed usually during the rainy season as food is more
readily available.

Cycle varies and is related to location and rainfall patterns. Fertilization is
internal. Positive correlation exists between the body size of the female and the number of
offspring she produces. Gestation lasts usually 6-8 months. Female moves in and out of the sun during their gestation period which allows them to keep their embryos at a constant temperature. Some evidence of long term sperm storage by the female to delay fertilization exists. No parental care. Females will mate with more than one male during the mating season.


Species gives birth to live young, up to 80 at one time, each about 30cm long (Carnley, 1996). This number can vary from 5-85 viviparous young that weigh around 6.1 – 20.2 grams each. They are brighter coloured than their parents, with either beige or yellow tails as seen in Fig. 3. Semi arboreal; actively climb trees, but tend to lose this habit when they become adults. The young are considered dangerous as they born with venom glands. Juveniles may exhibit caudal luring (shaking the tail) to attract prey.


Thoroughly irascible, irritable snake. Quick to strike and very deadly; readily feared for its strong and fast-acting hemotoxic venom. According to Boos (2014) this is “a unique snake that has the ability to literally blend invisibly into their background”. Bothrops is known to “ambush their pursuers: they initially flee but then make a 180 degree lightning quick turn” to wait until they get within striking range. When all other defense mechanisms fail, the mapepire gives off a distinctive defensive musk from its cloaca. Species is said to be nervous,
unpredictable and usually shy and tries to escape unless it feels as though it is being cornered. It vibrates its tail as well as enlarges its body to seem bigger. It has the ability to strike repeatedly, requiring no fixed coil. It can strike at heat and movement, often giving a ‘dry’ bite to partly envenomate the threat.

Related: Labaria Shows Up at Man’s Front Door in Guyana and Kills Pet


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