Yarará Lancehead

Bothrops jararaca—known as the jararaca or yarara—is a highly venomous pit viper species endemic to South America in southern Brazil, Paraguay, and northern Argentina. The specific name, jararaca, is derived from Old Tupi îararaka. Within its geographic range, it is often abundant and is an important cause of snakebite. No subspecies are currently recognized.

The drugs known as angiotensin converting enzyme (ACE) inhibitors, used for the treatment of hypertension and some types of congestive heart failure, were developed from a peptide found in the venom of this species.

Description

This is a slender and terrestrial species that grows to a maximum total length of 160 cm (63 in), although the average total 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 to form a lacunolabial, and 9–13 sublabials (usually 10–12). Midbody, there are 20–27 rows of dorsal scales (usually 23–25). The ventrals number 170–216 (rarely 218) and the 51–71 subcaudals 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. The dorsal ground color 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.

Behavior

This snake usually hunts at night, and during the day takes shelter in foliage; in habitats at higher altitudes and those with colder months, there is a significant reduction in activities, with greater activity observed during the warmer months. They are ambush predators and equipped with good camouflage; juveniles use caudal luring to attract and capture prey, making movements with the tip of the tail, which is white and appears very similar to an insect larva.

Common names

The English common name is jararaca. In Argentina, it is called yarará and yararaca perezosa. In Brazil, it is referred to as caissaca, jaraca, jaracá, jararaca, jararaca-do-rabo-branco, jararaca-do-campo, jararaca-do-cerrado, jararaca-dormideira, jararaca-dominhoca and malha-de-sapo. In Paraguay and Uruguay, it is also called yarará.

Geographic range