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Wildlife Guide · Brazil & Colombia

Green Anaconda

Eunectes murinus

The heaviest snake on Earth, a silent giant of South America's flooded forests.

Least Concern (IUCN 2021) — but newly split species means parts of its range are unassessed
A massive olive-green Green Anaconda with black oval blotches coiled at the edge of a slow-moving Amazon wetland, its eyes and nostrils set high on the head as it lies half-submerged in dark water

Image: Source: Wikimedia Commons via Wikipedia “Green anaconda” — verify license before production

In brief

A Green Anaconda (Eunectes murinus) is a large, non-venomous, semi-aquatic constrictor snake from tropical South America that is the heaviest snake in the world, killing prey by coiling and squeezing rather than biting.

By the WARN Research & Conservation TeamChecked against IUCN Red List & CITES sourcesLast updated

The Green Anaconda (Eunectes murinus) is the world's heaviest snake and one of its longest, a non-venomous constrictor that haunts the slow rivers, swamps and seasonally flooded grasslands of tropical South America. Females dwarf males, reaching lengths over 5 metres and weights near 100 kilograms. In 2024 scientists confirmed that what was long called the green anaconda is in fact two species, reshaping how we count and protect these giants.

~250 kg

Weight of the heaviest snake on Earth

5+ m

Typical length of a large female

20-40

Live young born per litter

Appendix II

CITES trade-controlled listing

Figures sourced from IUCN Red List — Eunectes murinus (Green Anaconda), Smithsonian's National Zoo — Green Anaconda, Rivas et al. 2024, Diversity (MDPI) — Disentangling the Anacondas: a New Green Species and other references on this page.

Green Anaconda: Quick Facts

Vital statistics and key facts about the Green Anaconda
Lifespan ~10 years wild; 30+ years in captivity
Weight Up to ~250 kg; heaviest verified ~97.5 kg female
Length Females commonly 5+ m; males average ~3 m
Diet Carnivore: fish, birds, capybara, deer, caimans
Gestation 6-7 months (live birth in water)
Young per litter 20-40 typically, occasionally up to ~100
Size at birth ~70-80 cm long, fully independent
Baby name Neonate / snakelet
Group name Bed or knot of snakes
CITES Appendix II

Scientific Classification

Scientific classification of the Green Anaconda
Kingdom Animalia
Phylum Chordata
Class Reptilia
Order Squamata
Family Boidae
Genus Eunectes
Species Eunectes murinus (Linnaeus, 1758) — Southern Green Anaconda; the northern populations were split off as E. akayima in 2024

Conservation Status

IUCN Status
Least Concern (IUCN, assessed 2021)
Population
No reliable estimate
Trend
Stable (per IUCN), though population data are limited
Assessed
2021
CITES
Appendix II

The 2024 recognition of the Northern Green Anaconda (Eunectes akayima) as a separate species means the former 'green anaconda' range is now split; the northern lineage has not yet been separately Red List assessed, so the Least Concern status is best read as honest-but-incomplete.

Did you know?

The Green Anaconda is so heavy that on land it can barely support its own bulk — it relies on water to carry its weight, which is why this 250 kg giant spends most of its life half-submerged.

Key Facts: Green Anaconda

  • The Green Anaconda is the heaviest known snake, with verified females weighing close to 100 kg and exceeding 5 metres in length.
  • It is non-venomous and kills by constriction, suffocating prey such as capybara, caimans, deer and large birds before swallowing them whole.
  • Females are far larger than males, a striking case of reverse sexual size dimorphism among snakes.
  • Anacondas give birth to live young in water (they are ovoviviparous), producing roughly 20 to 40 babies per litter, occasionally many more.
  • In 2024 the northern green anaconda was described as a separate species, Eunectes akayima, meaning much of the former range is now taxonomically split.
  • The species is listed as Least Concern by IUCN but is traded under CITES Appendix II because of demand for skins and the exotic pet trade.

Behaviour and ecology

Green Anacondas are ambush predators built for water. Their eyes and nostrils sit on top of the head, letting them lie almost fully submerged while watching for prey. Despite their bulk they move sluggishly on land but swim with ease, using the buoyancy of water to support their enormous mass. They are apex predators across their wetland range, taking fish, birds, mammals, caimans and capybara, and they may go weeks between meals after a large kill. Solitary for most of the year, they congregate only to breed, when several smaller males may court a single giant female in a so-called breeding ball. Females then carry developing young internally for six to seven months and give birth to live offspring in the water, each newborn already 70 to 80 cm long and entirely independent.

A giant recently split into two species

For centuries the green anaconda was treated as a single wide-ranging species. In February 2024 a team of researchers used genetic analysis to show that anacondas north of the Andes and Amazon differ from southern populations by about 5.5 percent in their DNA, having diverged nearly 10 million years ago. They named the northern lineage the Northern Green Anaconda, Eunectes akayima, leaving Eunectes murinus as the Southern Green Anaconda found across the Amazon and adjoining basins. This matters for conservation: a species once assumed to be abundant everywhere is now two separate entities, and the northern one has yet to receive its own formal Red List assessment, leaving real gaps in what we know about its numbers and threats.

Threats and the skin and pet trade

Although the Green Anaconda has a vast range and is not currently considered globally threatened, it faces mounting pressure. Wetlands are drained and degraded for agriculture, cattle ranching and infrastructure, fragmenting the slow waters anacondas depend on. The animals are killed out of fear, hunted for their large patterned skins, and captured live for the international exotic pet trade, which is why all anacondas are listed on CITES Appendix II to keep commercial trade monitored. Pollution and the loss of prey species add further strain. Because reliable population counts do not exist for most of the range, local declines can go unnoticed until they are severe.

What rescue and protection involve

Protecting Green Anacondas is less about captive rescue and more about keeping their wetlands intact and reducing needless killing. On-the-ground work in range countries includes safely relocating snakes that wander into farms and villages, intercepting animals destined for the illegal skin and pet trade, monitoring populations so declines are caught early, and teaching communities that a healthy anaconda population signals a healthy wetland. Because the species spans many countries and has just been split in two, sound field data and local stewardship are now more valuable than ever.

Green Anaconda vs Yellow Anaconda vs the new Northern Green Anaconda

FeatureGreen Anaconda (E. murinus)Yellow Anaconda (E. notaeus)Northern Green Anaconda (E. akayima)
StatusHeaviest snake; Least ConcernSmaller; Least ConcernSplit off in 2024; not yet assessed
Typical female size5+ m, up to ~100 kg~3-4 m, much lighterComparable to green anaconda; very large
ColourOlive-green with black blotchesYellow-gold with dark blotchesGreen like E. murinus; ~5.5% genetic difference
Main rangeAmazon and adjoining basins (incl. Brazil, Colombia)Paraguay-Paraná basin, southern South AmericaOrinoco Basin and northern South America

What WARN Does

WARN CIC is a registered global not-for-profit animal welfare organisation that funds local partner shelters, sanctuaries and rescue teams rather than running its own field stations. Its funded focus sits across a network of partner countries, two of which, Brazil and Colombia, fall squarely within the Green Anaconda's range. There, supporting partners means backing the people who relocate anacondas safely away from conflict, help curb the illegal skin and pet trade, and protect the flooded forests and wetlands these giants need. Across the wider South American range that lies outside WARN's funded countries, its role is education and awareness rather than direct operations — an honest division WARN is careful not to overstate.

Anacondas survive only where their wetlands do. By backing WARN's local partners in Brazil and Colombia, your gift helps the people who keep these flooded forests intact and these giants safe from the skin and pet trade.

Support Habitat Protection Donate to WARN

Green Anaconda: Frequently Asked Questions

How long do Green Anacondas live?
In the wild Green Anacondas typically live around 10 years, but in captivity they can reach 30 years or more, with the oldest recorded individual living over 37 years.

What do Green Anacondas eat?
They are carnivorous constrictors that eat fish, birds, mammals and reptiles. Large adults take big prey such as capybara, deer, caimans and large birds, killing by constriction and swallowing the animal whole.

How big do Green Anacondas get?
Green Anacondas are the heaviest snakes on Earth. Females, which are much larger than males, commonly exceed 5 metres and can weigh close to 100 kg; males average around 3 metres.

Are Green Anacondas dangerous to humans?
Green Anacondas are non-venomous and attacks on people are extremely rare. They are powerful constrictors, so very large individuals could pose a risk, but they generally avoid humans and are not a common danger.

How many Green Anacondas are left in the wild?
There is no reliable global population estimate. IUCN lists the species as Least Concern because of its very large range, but actual numbers are unknown, and the 2024 split into two species adds further uncertainty.

What is a baby Green Anaconda called?
A baby anaconda is called a neonate or simply a snakelet. Born live in water, each newborn is already about 70 to 80 cm long and fends for itself immediately with no parental care.

Where do Green Anacondas live?
Green anacondas haunt the slow rivers, swamps and seasonally flooded grasslands of tropical South America. They are semi-aquatic ambush predators: eyes and nostrils sit on top of the head so they can lie almost fully submerged while watching for prey. Wetland drainage for agriculture and cattle ranching is a growing threat across their range.

Sources & References

Population figures, conservation status and biological facts on this page are drawn from authoritative scientific and intergovernmental sources.

Terms used on this page

Plain-English definitions, from our wildlife and conservation glossary.

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