Jararaca

Fascinating facts about the Jararaca

• Between 1902 and 1945, jararaca bites made up 52% of all snakebite cases in southeastern Brazil – that’s 3,446 incidents in just 43 years. The snakes delivered an average of 25-26 mg of dried venom per bite, enough to kill a 60 kg human with just 70 mg. This shows how a single species can dominate public health risks in its range.
• A single adult jararaca can pump out as much as 300 mg of dried venom, far exceeding the typical 25-26 mg dose. That spike is enough to cause severe bleeding, kidney failure, and even intracranial hemorrhage in victims. It highlights the snake’s potent biochemical arsenal, which is why prompt antivenom treatment is critical.
• When researchers isolated a peptide from jararaca venom in 1965, it became the basis for ACE-inhibitor drugs that are used for the treatment of hypertension and some types of congestive heart failure. The discovery by Brazilian scientist Sérgio Henrique Ferreira turned a deadly toxin into a life-saving medicine.
• Juvenile jararacas spend about three-quarters of their meals on frogs and arthropods, while adults switch to mammals, with 80% of their diet consisting of rodents. This ontogenetic shift mirrors the snake’s growth from small-prey ambush hunter to a larger predator of vertebrates. It reveals a flexible feeding strategy that helps the species thrive across habitats.
• Mating season for jararacas peaks in April and May, and females give birth from February to April, usually delivering 10-14 young per litter. Both sexes reach sexual maturity at around two years old, allowing populations to rebound quickly after losses. This rapid turnover explains why the species remains abundant even in heavily impacted forests.

At a glance

About the Jararaca

The jararaca (Bothrops jararaca) is a sleek, terrestrial pit viper that can reach up to 160 cm (63 in) in total length, though most individuals are considerably shorter. Its head bears a distinctive dark brown stripe that runs from behind the eye to the mouth angle, bordered by a pale band, while the iris glints gold to greenish-gold with subtle reticulations. The body’s dorsal ground color ranges from tan and brown to gray, yellow, olive, or almost maroon, overlaid with pale-edged, dark-brown, subtriangular or trapezoidal markings that converge at the vertebral line. Juveniles display a striking white tip on the tail, a feature they wield as a lure, flicking the tip like an insect larva to entice prey. The scalation is intricate: 5–12 weakly keeled intersupraoculars, typically eight supralabials with the second fused to the prelacunal, and 20–27 rows of dorsal scales at mid-body. Their venom, a potent cocktail yielding 25–26 mg of dried toxin on average, has been a double-edged sword, responsible for over half of the snakebites recorded in southeastern Brazil between 1902 and 1945, yet also the source of the ACE-inhibitor peptides that revolutionized hypertension treatment.

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