Terciopelo

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 colors on its dorsal and ventral sides and it exhibits a postorbital stripe. The ventral side is yellow, cream, or a whitish gray, with dark blotches that are more frequent closer to the posterior end. Ventrolaterally, B. asper has interchanging gray 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, gray, 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 meters (3.9 to 5.9 ft) in length. …

It is found on the Gulf - Atlantic versant of eastern Mexico as far north as the state of Tamaulipas, southward through the entire Yucatán Peninsula extending into 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, it is found in Colombia, Ecuador, Guyana and Venezuela. The type locality given is "Obispo, on the Isthmus of Darien" (Panama). This is mostly a lowland species that, in Mexico and Central America, occurs from about sea level to 1,200 to 1,300 meters (3,900 to 4,300 ft) altitude. In South America, it apparently ranges to considerably higher elevations: up to 2,500 metres (8,200 ft) in Venezuela and at least 2,640 metres (8,660 ft) in Colombia according to herpetologist Lancini. According to Campbell and Lamar (2004), its range in Ecuador extends as far south along the Pacific coast as El Oro Province and the Vilcabamba area of the Río Catamayo Valley. This species is reported to occur from seven (Bolívar, Carchi, Chimborazo, Esmeraldas, Guayas, Los Ríos and Pichincha) of the fourteen provinces along the Pacific slope of Ecuador. There are even a few records from northern coastal Peru, with these snakes being reported in the Tumbes Region. …

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. When cornered or threatened, this species can be very defensive and may exhibit an S-coiled defense display. Juveniles are often semiarboreal, and even adults are sometimes encountered in bushes and low trees. Juveniles are also known to 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. 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".

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. …

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.