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, Reptiles of Ecuador says that reports of green anacondas 11.4 meters long or weighing 227 kilograms have not been confirmed. 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). 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.

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. Green anaconda males have longer anal spurs (about 7.5 millimeters) than females (about 5 millimeters), even though females are much bigger. 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. Full-grown female green anacondas have few enemies because they are so big.

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 do not lay eggs. A mother gives birth to live babies. Sometimes many male anacondas gather around one female in a group called a breeding ball; the largest litter on record, as of November 2026, had 82 young. Green anacondas are ready to have young at about 3 to 4 years old. Green anacondas are mostly solitary, which means they live alone, except when they breed.

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 typically live in swamps, marshes and slow-moving streams. River-dwelling green anacondas are often larger and heavier than those living in savanna. In the dry season a green anaconda's home range is about 0.25 square kilometers. In the wet season it is about 0.35 square kilometers. Green anacondas migrate an average of 1.3 kilometers between the areas they use in the dry and rainy seasons; the yellow anaconda lives south of the green anaconda, in areas such as the Pantanal and Chaco. Green anacondas in seasonally flooded areas must find water in the dry season or bury themselves in the mud.

A green anaconda has its eyes and nose on top of its head, so it can see and breathe while most of its body is under the water; a green anaconda's sight and hearing are more poorly developed than its senses of smell, heat and vibration. A green anaconda flicks its tongue to pick up scents in the air. A green anaconda has heat-sensing pits on its upper lip that help it find warm animals. A green anaconda can feel the vibrations of animals moving nearby. A green anaconda is not a very active hunter. It waits in the water for animals to swim by or come to the water to drink. A green anaconda is olive-green with dark oval spots. The color and spots of a green anaconda help it blend in with the plants in the wet places where it lives.

The U.S. Geological Survey says, as of November 2026, that the green anaconda is a nonvenomous ambush predator. A green anaconda is a constrictor: it wraps its strong body around its food and squeezes. Grown green anacondas eat large animals, such as deer and capybaras. Young green anacondas eat small animals, such as fish. Prey eaten by green anacondas usually weighs from 14% to 50% of the snake's own mass; the slow digestion of a green anaconda often takes days or weeks. After a big meal, a green anaconda can go weeks or even months without eating. Green anacondas are most active in the early evening. A group of anacondas is called a bed or a knot.

A green anaconda spends most of its time in the water; a green anaconda is an excellent swimmer. The name Eunectes, the group name for anacondas, means good swimmer. As of November 2026, a green anaconda can stay under water for about 10 minutes. A green anaconda rests in the sun on river banks and on tree branches that hang over the water; a green anaconda warms itself by changing how much of its body is in the sun. Green anaconda skin is soft and loose and can endure long periods of water absorption. 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

• clutches: sets of young
• ambush: a hidden wait
• nonvenomous: without venom
• expedition: a research trip