Bothrops jararaca
Bothrops jararaca is a venomous pitviper species found in southern Brazil, Paraguay and northern Argentina. The species name is derived from the Tupi words yarara and ca, which means "large snake." Within its range it is often abundant and is an important cause of snakebite. No subspecies are currently recognized.

# Description
This is a slender and terrestrial species that grows to a maximum length of 160 cm, although the average length is much less.
The head scalation includes 5-12 intersupraoculars that are weakly keeled, 7-9 supralabials (usually 8) of which the second is fused with the prelacunal, and 9-13 sublabials (usually 10-12). Midbody there are 20-27 dorsal scales (usually 23-25). The ventrals number 170-216 (rarely 218) and there are 51-71 subcaudals that are mostly paired.
The color-pattern is extremely variable, consisting of a dorsal ground color that may be tan, brown, gray, yellow, olive, or almost maroon. Midbody, this color is usually somewhat lighter than the head, anterior and posterior. This is overlaid with a series of pale-edged, dark brown subtriangular or trapezoidal markings on either side of the body, the apices of which reach the vertebral line. These marking may be situated opposite each other, or partially or completely juxtaposed; most specimens have a pattern with all three variations. In juveniles, the tip of the tail is white.
The head has a prominent, dark brown stripe that runs from behind the eye on either side of the head back to the angle of the mouth, usually touching the last three supralabials. Dorsally, this stripe is bordered by a distinct pale area. The tongue is black and the iris is gold to greenish gold with slightly darker reticulations.

# Common names
The English common name is jararaca. In Argentina it is called yararaca and yararaca perezosa. In Brazil it is referred to as caissaca, jaraca, jaraca, jararaca, jararaca-de-matta-virgem, jararaca-do-rabo-branco, jararaca-do-campo, jararaca-do-cerrado, jararaca-dormideira, jararaca-dominhoca, jararaca-preguicosa and malha-de-sapo. In Paraguay it is called yarara.

# Geographic range
Found in southern Brazil, northeastern Paraguay and northern Argentina (Misiones). The type locality is listed as "Lagoa d'Arara am Mucuri" (Brazil) by Wied-Neuwied in 1825. Occurs from near sea level to over 1,000 m altitude.

# Habitat
Prefers deciduous tropical forests and savanna country, as well as semi-tropical upland forests. It is said to favor open areas, such as farmland, with nearby vegetation cover.

# Feeding
They prey on birds and small mammals.

# Reproduction
Ovoviviparous. They are believed to produce about twenty young at a time.

# Venom
This species is often abundant within its range, where it is an important cause of snakebite. It is the most well-known venomous snake in the wealthy and heavily populated areas of southeastern Brazil, where is was responsible for 52% (3,446 cases) of snakebite between 1902 and 1945 with an 0.7% mortality rate (25 deaths).
The average venom yield is 25-26 mg with a maximum of 300 mg of dried venom. The venom is quite toxic. In mice, the LD50 is 1.2-1.3 mg/kg IV, 1.4 mg/kg IP and 3.0 mg/kg SC. For humans, the LD50 is estimated to be 210 mg SC.
Typical envenomation symptoms include local swelling, petechiae, bruising and blistering of the affected limb, spontaneous systemic bleeding of the gums and into the skin, subconjunctival hemorrhage and incoagulable blood. The systemic symptoms can potentially be fatal and may involve hemostatic disorders, intracranial hemorrhage, shock and renal failure.
The drug, captopril, which is used for the treatment of hypertension and some types of congestive heart failure, was developed from a peptide found in the venom of this species.