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). Zoo fact sheets say a green anaconda can reach 30 feet (9 meters) in length. 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 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.

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. Green anacondas are ready to have young at about 3 to 4 years old. Green anacondas breed about every other year, which lets the female recover from the energy that breeding takes.

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. 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. Green anacondas are mostly solitary, which means they live alone, except when they breed.

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 a constrictor: it wraps its strong body around its food and squeezes. Prey eaten by green anacondas usually weighs from 14% to 50% of the snake's own mass.

Grown green anacondas eat large animals, such as deer and capybaras. Young green anacondas eat small animals, such as fish. 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.

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. A green anaconda rests in the sun on river banks and on tree branches that hang over the water. 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

• Eunectes: anaconda group
• constrictor: a squeezing snake
• digestion: breaking down food
• migrate: move between places