Bothrops asper is a highly venomous pit viper species the range of which extends from southern Mexico to northern South America. They are found in a wide range of lowland habitats, often near human habitations.

Bothrops asper


Because of its proximity to human habitations and its defensive temperament, it is more dangerous to people than many other snakes. This species is the main cause of snakebite incidents within its range. No subspecies are currently recognized.
The generic name, Bothrops, comes from the Greek words bothros and ops, which mean “pit” and “face” (or “eye”), respectively. This is a reference to these snakes’ highly sensitive heat-detecting pit organs. The specific epithet, asper, which is a Latin word meaning “rough” or “harsh”, may allude to the species’ keeled dorsal scales.
Some of the common names applied to this snake are terciopelo (“velvet” in Spanish), fer-de-lance, Fer-de-lance (St.Lucia), 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 is commonly used in English to refer to this species, as well as to B. atrox, although B. atrox is more commonly referred to as the “lancehead” in North America. The name fer-de-lance is not used in the countries inhabited by this species.
Bothrops species can be distinguished by their broad, flattened heads which are set apart from the rest of their bodies. The head of this snake is light to dark brown or even black.
Although usually absent, it may have occipital blotches or streaks that range from indistinct to distinct. The underside is most often pale yellow. This species has different patterns and colours on its dorsal and ventral sides and it exhibits a postorbital stripe. The ventral side is yellow, cream, or a whitish grey, with dark blotches that are more frequent closer to the posterior end. Ventrolaterally, B. asper has interchanging grey scales which are more pale towards the medial line. Dark triangles with pale edges can be seen laterally, which range in number from 18 to 25. Apices either alternate or are reflective of each other over the middorsal line. In the interspaces, there are dark, paravertebral blotches. Specimens may have a yellow zig-zag-shaped line on each side of the body. There is a great variety of colours on its dorsal side: olive, grey, light brown to dark brown, tan or sometimes nearly black. To prevent water loss where they occur in drier regions, this species has more scales.
Specimens of this species may weigh up to 6 kilograms (13 lb) and are often 1.2 to 1.8 metres (3.9 to 5.9 ft) in length. Very big females can reach lengths up to 2.5 metres (8.2 ft), although this is uncommon. These are among the most sexually dimorphic of all snakes. The two sexes are born the same size, but by age 7 to 12 months, females begin to grow at a much faster rate than males. 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.
Across its geographic range, this species varies greatly phenotypically. As a result, great confusion between it and other related species, most notably Bothrops atrox, which is similar in colour but usually has yellow or rust-like tones and rectangular or trapezoidal blotches.
Male-male combat in this species has not been observed. Females will mate with more than one male during mating season. Mating includes a series of movements of the male, which then slowly chases an accepting female. The female then stops movement and extends her posture to mate. It is not known whether this species exhibits annual or biannual reproduction.
B. asper is nocturnal and solitary. It is less active in colder and drier periods.
This species is 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.
Despite being one of the most venomous snakes in Central and South America, the snake is sometimes preyed on by goliath spiders.
When cornered or threatened, this species can be very defensive and may exhibit an S-coiled defence display. Juveniles are often semi-arboreal, and even adults are sometimes encountered in bushes and low trees. Juveniles are also known to exhibit caudal luring, a use of their differently coloured tail tips to lure prey. Although both males and females display this behaviour, only males have bright coloured tail tips.
Compared to the common lancehead, B. atrox, these snakes have been described as excitable and unpredictable when disturbed. 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. In a review of bites from this species suffered by field biologists, Hardy (1994) referred to it as the “ultimate pit viper”. [Source: Wikipedia]

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