Anacondas are a group of large, non-venomous constrictor snakes native to South America. These semi-aquatic reptiles belong to the genus Eunectes, a name derived from Greek, meaning “good swimmer”. While often broadly referred to as a single entity, there are four distinct anaconda species.
Green Anaconda
The green anaconda, Eunectes murinus, is the world’s heaviest and one of its longest snakes. Adult females are significantly larger than males, often reaching lengths of up to 6.32 meters (20 feet 9 inches) and weighing between 30 to 80 kilograms (66 to 176 pounds). Its coloration is typically an olive-green to brownish-green base, adorned with circular black markings along its body and yellow scales on its belly, providing effective camouflage in its aquatic environment.
These snakes primarily inhabit swamps, marshes, and slow-moving streams and rivers within the tropical rainforests and seasonally flooded savannas of the Amazon and Orinoco basins. Their eyes and nostrils are positioned on top of their heads, allowing them to remain almost entirely submerged while waiting for prey. The green anaconda’s range spans across much of tropical South America, east of the Andes, including countries like Colombia, Venezuela, Brazil, Ecuador, Peru, Bolivia, Guyana, French Guiana, Suriname, and the island of Trinidad.
Yellow Anaconda
The yellow anaconda, Eunectes notaeus, also known as the Paraguayan anaconda, is considerably smaller than its green counterpart. Adults typically grow to lengths of 3 to 4.6 meters (10 to 15 feet) and can weigh between 25 to 35 kilograms (55 to 77 pounds). Its distinguishing feature is a yellowish-brown or greenish-yellow base color with prominent black spots, blotches, or streaks that wrap around its body, aiding camouflage in its wetland habitats.
This species predominantly inhabits the southern parts of South America, preferring swamps, marshes, and slow-moving rivers and streams. It is commonly found in the Pantanal wetlands, with a geographical distribution that includes Paraguay, southern Brazil, northeastern Argentina, and Bolivia. They spend a significant portion of their time in water, using their coloration to blend into murky environments.
Dark-spotted Anaconda
The dark-spotted anaconda, Eunectes deschauenseei, is characterized by a darker base color and more pronounced, often irregular, dark spots compared to other anaconda species. This species is generally smaller than the yellow anaconda, with adult males measuring between 1.3 to 2.11 meters (51 to 83 inches) and females up to 2.31 meters (91 inches) in snout-to-vent length. Its unique appearance helps it blend into the swampy, seasonally flooded freshwater areas it inhabits.
Its geographical range is more restricted, primarily found in northeastern South America, specifically in northern Brazil (Pará and Amapá states) and French Guiana. The species is also noted to occur in the Marajó Island region of Brazil. This anaconda is less commonly observed than the green or yellow anacondas.
Bolivian Anaconda
The Bolivian anaconda, Eunectes beniensis, is a distinct species that was once believed to be a hybrid of the green and yellow anacondas due to its intermediate physical characteristics. This snake typically exhibits a brownish-yellow or greenish-yellow base color with distinct dark markings, similar to both E. murinus and E. notaeus. It can reach lengths between 3.3 to 4.4 meters (11 to 14 feet) and weigh up to 35 kilograms (77 pounds).
The Bolivian anaconda’s range is almost exclusively confined to the Beni Department of Bolivia, where it prefers wetlands and other muddy, swampy, or flooded areas. This specific geographical limitation distinguishes the species. While sharing some visual similarities with other anacondas, genetic and morphological evidence confirms its status as a separate species.