Bothrops Asper

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. 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."

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. 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.

It is found in the Atlantic lowlands of 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, it is found in Colombia, Ecuador, Guyana and Venezuela. The type locality given is "Obispo, on the Isthmus of Darien" (Panama).

This species likes moist environments, and occurs in most life zones located at low or middle elevations (up to 600 metres (2,000 ft)), excluding those with strong seasonal dry periods. They are, however, sometimes found at much higher elevations. This is true 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.

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.

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.

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.

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.

Despite being one of the most venomous snakes in Central and South America, the snake is sometimes preyed on by goliath spiders.