Published April 11, 2020. Updated July 15, 2020. Open access.

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Fer-de-Lance (Bothrops asper)

Reptiles of Ecuador | Serpentes | Viperidae | Bothrops asper

English common names: Fer-de-Lance, Central American Lancehead, Terciopelo, Yellow-Jaw Tommygoff.

Spanish common names: Equis de la costa, equis, rabihueso (Ecuador); barba amarilla, cuatronarices (Colombia); terciopelo, barba amarilla, nauyaca (Central America).

Recognition: ♂♂ 220 cmMaximum distance from the snout to the tip of the tail. ♀♀ 250.1 cmMaximum distance from the snout to the tip of the tail.. In Ecuador, the Central American Lancehead (Bothrops asper) may be identified by having a triangular-shaped head with a snout that is not upturned, heat-sensing pits between the eyes and nostrils, and a dorsal pattern of 14–28 pale X-shaped markings on a brownish dorsum.1,2 Newborn lanceheads have brightly-colored tail tips (yellowish in males and pink/whitish in females).3 In Ecuador, the most similar species that may be found living alongside B. asper are B. punctatus and B. osbornei, which are identified by their dark brown trapezoidal blotches or spots arranged in such a way that they form squares.4 The Ecuadorian Toadhead (Bothrocophias campbelli) has an upturned snout and comparatively much smaller eyes.5 The hognosed-pitvipers (genus Porthidium) have an upturned snout and a stout body.

Variation among individuals of Bothrops asper

Figure 1: Individuals of Bothrops asper from FCAT Reserve, Esmeraldas province, Ecuador (); Cerro de Hayas, Guayas province, Ecuador (); Morromico, Chocó department, Colombia (); Cerro Blanco Protected Forest, Guayas province, Ecuador (); Las Balsas Reserve, Santa Elena province, Ecuador (); Buenaventura Reserve, El Oro province, Ecuador (); and Canandé Reserve, Esmeraldas province, Ecuador (). j=juvenile.

Natural history: Generally frequentRecorded weekly in densities below five individuals per locality. to extremely commonLikely to be seen every day, usually in large numbers., especially in areas where prey is abundant, such as swamps,6 streams, and near mammal burrows,7 but uncommon in cold, pristine cloudforests.5 Bothrops asper inhabits old-growth to heavily disturbed evergreen to deciduous lowland and foothill forests, savannas, plantations (cacao, coffee, banana, and African palm), pastures, rural gardens, and even human dwellings.810 It also occurs, but is less abundant, in drier areas such as dry shrublands.7,10 During dry periods, individuals actively seek wetter spots near creeks and streams.2

Throughout the day, Central American Lanceheads typically remain coiled in the forest floor11 (usually close to logs, large trees, or clusters of dense vegetation)2 or sheltered in holes, below logs, or among roots,2,9 but others remain out in the open, basking in direct sunlight12,13 or moving at ground level.9,14 Within about an hour of sunset, most individuals emerge from their hideouts and move (usually less than 10 m) to their nocturnal ambush sites;12 others may remain hidden for 3–6 days, especially after a meal.6 During nights when the ambient temperature is ideal (21–31 °C),15 the vipers spend an average of 37 minutes moving, but they move less during cold nights.12 Although mostly sedentary, individuals can occasionally move up to 1.2 km in two nights.2 Individuals of Bothrops asper usually dwell on soil or leaf litter, but also sit-and-wait on the surface of slow-moving bodies of water,9 swim across rivers,12 or forage on arboreal vegetation up to 7 m above the ground.16,17 Overall, there is a tendency for juveniles to be more arboreal than adults.18,19 The home range size of the Fer-de-Lance is 0.59–13.81 ha (about the size of 1–19 soccer fields).12

Central American Lanceheads are ambush predators.12 They wait for prey to pass by. They can “bite and hold” their prey or “bite and release,” subsequently following the scent trail of the envenomated prey.12 As juveniles, they attract prey by means of moving their brightly colored tail as a lure.20 Terciopelos are opportunistic predators; they feed on almost any animal that is 3–75% of their body mass.2,21 Their diet includes primarily (69%) mammals (mostly rodents, but also rabbits, skunks, opossums, and even porcupines), but also amphibians (mostly frogs such as Leptodactylus labrosus, L. rhodomerus, Lithobates vaillanti, Pristimantis achatinus, Rhinella horribilis, and Smilisca phaeota, but also caecilians)9,22, lizards (whiptails, anoles, the microteiid Ptychoglossus gorgonae,1 and the worm lizard Amphisbaena alba),23 snakes (including Dipsas andiana,9 and members of their same species), birds, invertebrates (mainly centipedes,24,25 but also beetles, flies, hemipterans, ants, grasshoppers, and crayfish), fish,23 and carrion.2,2528 When consumed, some toxic frogs cause the vipers to be sluggish and incapable of moving for nearly an hour.29 The diet of the Fer-de-Lance seems to shift from being based primarily on ectothermic (“cold-blooded”) prey as juveniles to based mostly on endothermic (“warm-blooded”) animals as adults.30,31 Individuals obtain water from their prey, from dew-laden surfaces, and bodies of water.2

Terciopelos rely on their camouflage as a primary defense mechanism.2 When threatened, some snakes flee, others give a “warning” by wiggling their tail against the leaf litter, and some just readily attack.2,5 Predators of Bothrops asper include snakes (such as Clelia clelia, C. equatoriana, and Drymarchon melanurus),2,9 mammals (such as peccaries, skunks, coatis, and raccoons),1,2 falcons, hawks, chickens, crabs, and spiders (particularly tarantulas).2,9 There are records of adult Terciopelos being attacked and severely injured by monkeys.32 The Fer-de-Lance is parasitized by ticks, parasitic worms, and protozoans.2,33,34

The Fer-de-Lance is a venomous species (LD50The median lethal dose (LD50) is a measure of venom strength. It is the minium dosage of venom that will lead to the deaths of 50% of the tested population. 1.9–11.2 mg/kg)35,36 in which the venom of juveniles is more lethal, hemorrhagic, and kills more quickly than that of adults.3740 In humans, the venom typically causes intense pain, swelling, bruising, bleeding, blistering, defibrination (depletion of the blood’s coagulation factors), nausea and vomiting, numbness, impaired consciousness, fever, and necrosis (death of tissues and cells).4145 In pregnant women, it may cause fetal death.46 In poorly managed or untreated cases, it can cause amputations, permanent complications and disabilities (6% of cases), and even death (in 5–7% of cases).4749 The prognosis is usually bad for victims that reach a hospital over six hours after the bite and for those that use traditional medicine, especially if they were bitten by a snake longer than one meter in total length.45,50 Critically envenomated victims die from intracranial hemorrhage, acute renal failure, blood poisoning, or hemorrhagic shock.5052 However, some bites to humans involve no envenomation at all (“dry bites”).11 Bothrops asper causes 44.5–100% of snakebites throughout its range,47,53,54 probably because snakes of this species are perfectly camouflaged, abundant in agricultural areas,11,49 have a high venom yield (up to 1,530 mg or 5–6 cc of venom per bite)49,55 and toxicity, and have an aggressive self-defense behavior.30,44

“All the information which I have obtained concerning this reptile, wherever it is known, concurs in respect to the frightful effects of its bite. In a few hours the strongest man, in the best of health, becomes a corpse. The excitement of the nervous systems at first induced is followed by complete prostration; blood flows from every pore and life ebbs away with frightful rapidity. The Indians insist that the nauhyaca does not confine itself to biting when assaulted, but that it boldly attacks pedestrians, and even precipitates itself into boats coasting along the banks of a river. I will not endorse this statement, which seems to be at variance with the usual habits of serpents.”

Arthur Morelet, French naturalist, 1871.1

Fortunately, the antivenom available in Ecuador can, to a degree, neutralize the venom of Bothrops asper.57 However, the venom’s toxic and enzymatic activities differ drastically between populations35,58 and across age categories.38,39,59, For example, the protein similarities between the venom of two populations of Fer-de-Lance in Costa Rica may only be around 52%.58 Although serum therapy (antivenom) is the only recommended approach against a bite by a Terciopelo, extracts of some plants used by traditional “healers” may help alleviate and even neutralize the swelling and depletion of the blood’s coagulation factors caused by the envenomation.60

What to do if you are bitten by a Fer-de-Lance?

  1. Remain calm.
  2. Remove rings and tight fitting clothes to avoid swelling.11
  3. Reduce movement of bitten extremity to reduce absorption of venom.61
  4. Avoid the application of tourniquets, electric shocks, traditional medicine, venom suction, and incision of the bite wound.1,61
  5. Plan immediate evacuation to a medical facility that has antivenom and avoid any action that may delay transportation.
  6. At the medical facility, personnel can initiate treatment with the appropriate antivenom, monitor vital signs, and perform laboratory tests.11

Males of Bothrops asper become sexually mature when they reach ~99.5 cm in total length; females at ~111.3 cm, or in little over 3 years,62 although females may attain a length of >2 m and a weight of 6 kg in just 2.5 years.63 The breeding season of some Fer-de-Lance populations coincides with the rainy season.2 Females are capable of delaying fertilization by storing sperm for years.2 After a gestation period of 6–8 months, females “give birth” (the eggs hatch within the mother) to 2–102 young1,49 that are 21.5–37.1 cm in total length.50,62 Females usually produce only one litter per year if environmental conditions are favorable.62 In captivity, individuals can live up to 21 years.2

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Conservation: Least Concern Believed to be safe from extinction given current circumstances..64 Bothrops asper is listed in this category because the species is widely distributed, frequently encountered throughout its range, tolerates and even thrives in human-modified environments, and is considered to be facing no major immediate extinction threats.2 However, the Fer-de-Lance generally cannot survive in areas without vegetation cover.2 The substitution of traditional crops for mechanized agriculture is causing the species to be less frequently encountered or absent altogether in some areas.2,9 Other threats to the species include direct killing (terciopelos are usually killed on sight by humans alleging precautionary reasons),2,9,14 traffic mortality, and the decline in the abundance of prey. In a rainforest locality in Panama, the occurrence rates of B. asper have decreased to cero in the period from 1997 to 2012, probably as a result of the collapse of amphibian populations.65 Still, given the Terciopelo’s formidable capacity to adapt to new environments, it is unlikely that it will become extinct, at least not in the near term future.2

Distribution: Bothrops asper is native to the Neotropical lowlands and adjacent mountainous areas from Mexico to northwestern Peru. In Ecuador, it occurs at elevations between 0 and 1642 m.

Distribution of Bothrops asper in Ecuador

Figure 2: Distribution of Bothrops asper in Ecuador.

Etymology: The generic name Bothrops, which is derived from the Greek word bothros (meaning “pit”),66 refers to the heat-sensing pits between the eyes and nostrils. The specific epithet asper is a Latin word meaning “rough” or “harsh.” It probably refers to the skin on the dorsum of this species, which has a coarse texture.5

See it in the wild: Terciopelos can be located with ~10–30% certainty in forested or agricultural areas throughout western Ecuador. Some of the best localities to find Central American Lanceheads in the wild in Ecuador are: Bilsa Biological Reserve, Buenaventura Biological Reserve, Canandé Reserve, and Jama-Coaque Ecological Reserve. The snakes may be located by walking along trails at night.


Can you survive a viper bite?

Yes, you can. With a timely treatment based on the appropriate antivenom, your chance of surviving is close to 100%.

Can you eat a Fer-de-Lance?

Yes, it is possible. The meat of the Fer-de-Lance is not toxic. It does, however, usually have a variety of parasitic worms.2,33

Do vipers follow humans?

They don’t.1 In fact, in the case of the Terciopelo, there is evidence that the snakes actively avoid developed areas.12 They do, however, follow their prey, mostly rodents.12 Therefore, vipers such as the Fer-de-Lance are common where rat populations have exploded.5

How venomous is a Fer-de-Lance?

With a lethal dose of LD50 1.9–11.2 mg/kg, the venom of the Fer-de-Lance is considered “extremely toxic.”35,36 In poorly managed or untreated human envenomations, the venom may cause permanent complications and disabilities in 6% of cases, and death in 5–7% of cases.4749

Is the Fer-de-Lance the most venomous snake?

No, it is not. Many snake species are more venomous. However, the Fer-de-Lance is responsible for the majority (44.5–100%)47,53,54 of snakebites throughout its range because snakes of this species are perfectly camouflaged, abundant in agricultural areas,11,49 have a high venom yield (up to 1,530 mg or 5–6 cc of venom per bite)49,55 and toxicity, and have an aggressive self-defense behavior.30,44

What does a Fer-de-Lance eat?

The Fer-de-Lance has an opportunistic diet consisting largely (up to 69%) on mammals (mostly rodents, but also rabbits, skunks, opossums, and even porcupines), but also on amphibians, lizards, snakes, birds, invertebrates, fish, and carrion.2,26

Special thanks to Mahmood Sasa and Max Seldes for symbolically adopting the Fer-de-Lance and helping bring the Reptiles of Ecuador book project to life.

Click here to adopt a species.

Author: Alejandro ArteagaaAffiliation: Khamai Foundation, Quito, Ecuador.

Photographers: Jose VieiraaAffiliation: Tropical Herping (TH), Quito, Ecuador.,bAffiliation: ExSitu, Quito, Ecuador. and Sebastián Di Doménico.

How to cite? Arteaga A (2020) Fer-de-Lance (Bothrops asper). In: Arteaga A, Bustamante L, Vieira J (Eds) Reptiles of Ecuador: Life in the middle of the world. Available from: DOI: 10.47051/FEPX4083

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