Anaconda
Anacondas are large, nonvenomous snakes of the genus Eunectes in the boa family (Boidae), native to the tropical wetlands, swamps, and slow-moving rivers of South America east of the Andes. Four species are traditionally recognized: the green anaconda (E. murinus), the yellow anaconda (E. notaeus), the dark-spotted anaconda (E. deschauenseei), and the Bolivian anaconda (E. beniensis). A 2024 genetic study proposed splitting the green anaconda into a southern and a northern species (E. akayima), but that proposal remains debated among herpetologists. The origin of the English name is uncertain. One common theory traces it to a Tamil or Sinhalese word first applied to a snake in Sri Lanka and later transferred by Europeans to the South American giants. The genus name Eunectes comes from Greek and means “good swimmer.”
The green anaconda is the heaviest snake in the world. Large females can exceed 5 meters (16 feet) in length and weigh more than 90 kilograms (200 pounds). The reticulated python of Southeast Asia can grow longer, but it is far more slender. Anacondas show strong sexual dimorphism, with females much larger than males. They are semi-aquatic, and their eyes and nostrils sit high on the head, so they can watch and breathe while most of the body stays hidden underwater. As ambush predators, they seize prey with their jaws and kill it by constriction. Their diet includes fish, birds, turtles, capybaras, deer, and even caimans. After a large meal, an anaconda may go weeks or months without eating again.
Anacondas give birth to live young rather than laying eggs. A female typically produces 20 to 40 offspring, which are independent from birth. During the breeding season, several males may coil around a single female in a “breeding ball” that can last for weeks, and females have occasionally been documented eating males after mating. Adult anacondas have few natural predators besides humans and, rarely, jaguars or large caimans. The main threats to wild anaconda populations are habitat loss, hunting for skins, and killings driven by excessive fear. Despite their fearsome reputation in folklore and film, attacks on humans are extremely rare. Anacondas remain an important apex predator in South American wetland ecosystems and a lasting subject of scientific and popular interest.