Fer-de-lance

## Description

Terciopelo (Bothrops asper ) is a species of pit viper occurring at low to moderate elevations in northeast Mexico and Central America, and into South America where it is known from elevations up to 2600 meters in the Colombian and Ecuadorian Andes, as well as Venezuela and Trinidad on the Caribbean coast. With a mass up to 6 kilograms (13 lb) and the maximal length of 2.5 metres (8.2 ft), terciopelo is among the largest pit vipers. It is light to dark brown in color, often with yellow zig-zag-shaped line on each side of the body. Dubbed "the ultimate pit-viper" for its large size, fangs and venom yield, it has a fearsome reputation, responsible for the most snakebites within its range because of its defensive temperament and proximity to human residence. However, in common with other venomous snakes it avoids confrontation with humans whenever possible. No subspecies are currently recognized.

## Appearance

The Fer-de-lance is a highly venomous pit viper species found from southern Mexico to northern South America. It is the most dangerous snake of Central and South America and is the main cause of fatal snakebite incidents within its range. These snakes can be distinguished by their broad, flattened heads which are set apart from the rest of their bodies. Their head is light to dark brown or even black in color. The underside is most often pale yellow. This species has different patterns and colors on its dorsal and ventral. The ventral side is yellow, cream, or a whitish-gray, with dark blotches that are more frequent closer to the posterior end. Some individuals may have a yellow zig-zag-shaped line on each side of the body. There is a great variety of colors on their dorsal side: olive, gray, light brown to dark brown, tan or sometimes nearly black. Females have thick, heavy bodies and grow significantly larger than males. They also have heads two or three times the size of males relative to their size and proportionally bigger fangs (typically 2.5 cm), as well.

## Distribution

Fer-de-lances are found in eastern Mexico and Central America, including Guatemala, Belize, Honduras, Nicaragua, Costa Rica, and Panama. An isolated population occurs in southeastern Chiapas (Mexico) and southwestern Guatemala. In northern South America, these snakes are found in Colombia, Ecuador, Guyana, and Venezuela. Fer-de-lances like moist environments. They can be found in the premontane forest in Costa Rica, the cloud forest of Guatemala and Mexico, or the lower montane wet forest in the Caribbean Region of Colombia and Ecuador. They chiefly inhabit tropical rainforest and evergreen forest, but will also occur in drier areas of tropical deciduous forest, thorn forest, and pine savannah near lakes, rivers, and streams.

## Behavior

Fer-de-lances are nocturnal and solitary snakes. They are less active in colder and drier periods. They are often found near rivers and streams, basking in the sun during the day and lying still while well camouflaged in leaf litter or under forest cover waiting to ambush prey such as rats and mice that come within range during the night. Juveniles are often semiarboreal, and even adults can sometimes be seen in bushes and low trees. Juveniles also exhibit caudal luring, a use of their differently colored tail tips to lure prey. Although both males and females display this behavior, only males have bright coloured tail tips. These snakes are excitable and unpredictable when disturbed. When cornered or threatened, Fer-de-lances can be very defensive and may exhibit an S-coiled defense display. They can, and often will move very quickly, usually opting to flee from danger, but are capable of suddenly reversing direction to vigorously defend themselves. Adult specimens, when cornered and fully alert, are dangerous. When cornered or threatened, Fer-de-lances can be very defensive and may exhibit an S-coiled defense display.

## Venom

B. asper, together with Crotalus durissus, is the leading cause of snakebite in Yucatán, Mexico.

It is considered the most dangerous snake in Costa Rica, responsible for 46% of all bites and 30% of all hospitalized cases; before 1947, the fatality rate was 9%, but this has since declined to almost 0% (Bolaños, 1984), mostly due to the Clodomiro Picado Research Institute, responsible for the production of snake antiophidic sera (which are also exported to other countries in Latin America and Africa) and scientific research on serpents and their venoms, as well as educational and extension programs in rural areas and hospitals.

In the Colombian states of Antioquia and Chocó, it causes 50–70% of all snakebites, with a sequelae rate of 9% and a fatality rate of 6% (Otero et al., 1992).

In the state of Lara, Venezuela, it is responsible for 78% of all envenomations and all snakebite fatalities (Dao-L., 1971). One of the reasons so many people are bitten is because of its association with human habitation; many bites occur indoors (Sasa & Vázquez, 2003).

Herpetologist Douglas March died after being bitten by this species.

This species is irritable and fast-moving. It is also regarded as being more excitable and unpredictable than B. atrox. Its large size and habit of raising its head high off the ground can result in bites above the knee. It has also been observed to eject venom over a distance of at least 6 ft (1.8 m) in fine jets from the tips of its fangs (Mole, 1924).

Bite symptoms include pain, oozing from the puncture wounds, local swelling that may increase for up to 36 hours, bruising that spreads from the bite site, blisters, numbness, mild fever, headache, bleeding from the nose and gums, hemoptysis, gastrointestinal bleeding, hematuria, hypotension, nausea, vomiting, impaired consciousness and tenderness of the spleen. In untreated cases, local necrosis frequently occurs and may cause gangrene which often requires amputation. In 12 fatal cases, the cause of death was sepsis (5), intracranial hemorrhage (3), acute kidney injury with hyperkalemia and metabolic acidosis (2) and hemorrhagic shock (1).

Venom yield (dry weight) averages 458 mg, with a maximum of 1530 mg (Bolaños, 1984) and an LD50 in mice of 2.844 mg/kg IP.

The venomous bite of B. asper has been suggested to have been a factor in the choice of certain Mayan settlements, such as Nim Li Punit, Belize Central America, where the thick jungle inhabited by these snakes was used as a defensive boundary.

The venom of the fer-de-lance is so potent that didelphine opossums (i.e., opossums like the Virginia opossum), which are normally immune to the venom of pit vipers and rattlesnakes, are still capable of succumbing to the venom of this snake. This is especially the case if the opossum is not fully grown (and thus the venom is more concentrated per gram). Indeed, the extremely potent venom of B. asper has been suggested to have evolved as part of an evolutionary arms race between these snakes and didelphine opossums, as a defensive adaptation to prevent predation by opossums, an adaptation that allowed fer-de-lances to prey on large opossums, or both.

## Diet

Fer-de-lances are carnivores and feed on birds, amphibians, reptiles, and small mammals, mainly rats, and mice. Juveniles consume small frogs, lizards, and even large insects.

## Reproduction

Fer-de-lances have are polyandrous which means that females mate with more than one male during mating season. The breeding season of these snakes varies according to location. In some parts, mating takes place between September and November, with females giving birth between April and June. Some populations may mate in March, and give birth in September-November. The average number of offspring is 5-86 live young. In both populations, gestation time ranged from 6 to 8 months. Snakelets are born fully-developed and don't need parent care.

## Population

### Threats

The main threat to Fer-de-lances is habitat loss due to deforestation, agriculture, and urbanization. These snakes also suffer locally from environmental changes and the decline of their prey species.

### Ecological niche

Fer-de-lances are important predators in the ecosystem they live in as they control populations of species they prey on.

## Fun Facts

Other common names applied to this snake are Mapepire balsain (Trinidad), Carpet Labaria (Guyana), Barba amarilla (Guatemala, Honduras; "yellow beard"), equis (Ecuador and Panama; "x"), Taya equis (Colombia), Cuaima (Venezuela), Nauyaca (México; from Nahuatl nahui, four, and yacatl, nose; "four noses"), and Yellow-jaw tommygoff (Belize)

The name "fer-de-lance" means "spearhead" in French.

On average, these snakes inject 105 mg of venom in one bite while the fatal dose for a human is 50 mg.

To prevent water loss where they occur in drier regions, these snakes possess more scales than usual.