How big can a green anaconda grow? Green anacondas are one of the largest snakes in the world. As of November 2026, one reference says the true maximum size of a green anaconda is the subject of much dispute. Biologist Jesus Rivas began the Anaconda Project in 1992 to learn the basics of anaconda biology, as of October 2024. Rivas's long-term study found that the largest size expected, and the largest recorded, are well below the biggest sizes reported in the literature. As of February 2024, Reptiles of Ecuador gives the maximum total length, snout to tail tip, as 3.39 meters for males and 6.6 meters for females. As of February 2024, Reptiles of Ecuador gives the greatest weight of a green anaconda as up to 104.4 kilograms.

As of November 2026, the U.S. Geological Survey says large female green anacondas can reach a total length of up to 26 feet (8 meters). As of November 2026, Reptiles of Ecuador says that reports of green anacondas 11.4 meters long or weighing 227 kilograms have not been confirmed. In 2022 a team led by researchers from New Mexico Highlands University and the University of Queensland collected anaconda samples in the Ecuadorian Amazon on a 10-day expedition after a rare invitation from the Waorani people. On that expedition one female green anaconda was measured at 6.3 meters (20.7 feet) long. As of November 2026, the green anaconda is the heaviest snake in the world. You may have heard that the green anaconda is also the longest snake. In fact, National Geographic says, as of November 2026, that a reticulated python can reach slightly greater lengths than a green anaconda, but the green anaconda is much heavier.

Before the 2024 study, four species of anaconda were recognized: the green, yellow, dark-spotted and Beni (Bolivian) anacondas. In 2024 researchers reported that green anacondas are two species that split almost 10 million years ago and differ genetically by 5.5%. The Rivas team studied samples from all anaconda species across nine countries. The new species was named Eunectes akayima, the northern green anaconda, in a paper in the journal Diversity in February 2024 by Rivas and colleagues. Rivas says the two green species look almost identical, but males of the southern species grow larger than males of the northern species, as of October 2024.

As of May 2024, the 2024 split had been criticized: Dubois and colleagues and Vasquez-Restrepo and colleagues argued that the new name broke nomenclature rules. Critics also questioned an analysis based on three mitochondrial genes as unreliable, and questioned the clades the paper proposed. As of November 2026 the Reptile Database treats Eunectes akayima as a synonym of E. murinus, because it cannot be told apart by looks and is a sister clade. The Reptile Database notes that the yellow, dark-spotted and Beni anacondas are separate evolutionary species that are not completely reproductively isolated and may still hybridize.

The native range of the green anaconda is estimated at 623,511 square kilometers of lowlands east of the Andes, as of February 2024. Green anacondas live east of the Andes in tropical South America, mainly in the Amazon and Orinoco basins and the Guianas, and on the island of Trinidad. Green anacondas are found at higher densities in savannas, up to 0.36 per hectare, than in rainforests. National Geographic lists the population trend of the green anaconda as unknown, as of November 2026.

As of November 2026, breeding female green anacondas are at least five times the size of breeding males. That is the biggest size gap between the sexes of any land animal with a backbone. Rivas found that very large male anacondas may be mistaken for females and courted by smaller males, which may keep males from getting too big. Larger female anacondas produce larger clutches of larger young, but breed less often than smaller females. Green anacondas breed about every other year, which lets the female recover from the energy that breeding takes.

The International Union for Conservation of Nature (IUCN) lists the green anaconda as Least Concern, as of November 2026. Reptiles of Ecuador explains the Least Concern listing: the species is widely distributed, lives in many protected areas, and faces no major immediate extinction threats, as of November 2026. The northern green anaconda has a much smaller range than the southern one, so it may be more vulnerable, and the IUCN Least Concern rating depends in part on how widely a species is distributed, as of November 2026. As of February 2024, researcher Bryan Fry estimated that deforestation of the Amazon basin has caused 20 to 31% habitat loss, which may affect up to 40% of its forests by 2050. In Venezuela, human management of water has hurt savanna anaconda populations by raising the chance that they dry out, as of November 2026. Rivas concluded that harvesting wild anacondas is not likely to work, and recommended ecotourism.

The pregnancy of a green anaconda lasts about seven months, and the female does not eat during it. A newborn green anaconda averages 200 grams and 68 centimeters, about 1% of its mother's mass. A female green anaconda usually has 20 to 40 live babies at a time. Green anacondas breed about every other year, which lets the female recover from the energy that breeding takes. In the wild, a green anaconda lives about 10 years on average, as of November 2026. One recaptured green anaconda in the wild was found after 13 years and was estimated to be 20 years old, and captive ones may live up to 31.8 years, as of November 2026.

Words to know

• synonym: another name
• nomenclature: naming rules
• clades: branches of life
• ecotourism: nature visits