Eunectes murinus (Linnaeus, 1758)

Green anaconda (EN) | Groene anaconda (NL) | Aboma (SR)
Conservation status: Least Concern
Adult size: 3 - 8m, up to 150kg
Diet: Carnivore
Activity: Primarily nocturnal
Lifestyle: Primarily aquatic

Don't kill the Caterpillars, then complain there are no Butterlflies ~ John Marsden

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The green anaconda (Eunectes murinus), also known as the giant anaconda, is a remarkable snake species native to South America. It is one of the most impressive members of the boa family, known for its incredible size, aquatic lifestyle, and intriguing behaviors.
E. murinus

Size and Appearance:

The green anaconda is the heaviest snake globally, with mature specimens often reaching lengths of 5 to 5.21 meters. While there are claims of even larger individuals, these remain unverified. These massive snakes can weigh between 30 to 80 kilograms. Female green anacondas tend to be significantly larger than males, which average around 3 meters in length.

The snake's distinctive coloration consists of an olive green background adorned with black blotches running along its body. Its head is relatively narrow compared to its body, often marked with striking orange-yellow striping. Its eyes are strategically placed on the top of its head, allowing the snake to see out of the water while swimming without exposing its body. This unique adaptation enables it to stalk its prey stealthily.

Habitat and Distribution:

Green anacondas thrive in a range of aquatic environments, including swamps, marshes, lagoons, slow-moving streams, and rivers. They primarily inhabit the tropical rainforests and seasonally flooded savannas of the Amazon and Orinoco basins. Their aquatic lifestyle is facilitated by their streamlined bodies and the ability to remain submerged for extended periods.

The species' distribution covers a considerable expanse of South America, spanning countries such as Colombia, Venezuela, Ecuador, Peru, Bolivia, Brazil, the Guianas and the island of Trinidad. Their habitat preferences align with regions abundant in water sources, where they can efficiently hunt and conceal themselves.
The green anaconda is the largest snake in the world by mass


Green anacondas are apex predators with a diverse and opportunistic diet. They are known to consume a wide array of prey items, including fish, amphibians, birds, mammals, and other reptiles. They are also capable of consuming large prey, such as juvenile tapirs, deer, peccaries, capybaras, and caimans. Prey availability varies between grasslands and river basins, but in both habitats, green anacondas have been observed consuming prey that can reach up to 14% to 50% of their own body mass.


One of the most remarkable discoveries related to green anacondas is the phenomenon of facultative parthenogenesis. This means that females have the ability to reproduce without mating with males. In 2014, it was observed for the first time that a green anaconda in West Midland Safari Park gave birth to three young through parthenogenesis. Subsequent genetic research confirmed additional instances of parthenogenesis in this species.

Reproduction and Reproductive Behavior:

These snakes follow a solitary lifestyle until the mating season, which varies depending on locality. During this time, female anacondas release pheromones to attract males. In some cases, many males will locate the same female and compete to mate with her. These breeding balls can consist of up to 12 males simultaneously attempting to court the female. This courtship and mating process is nearly exclusively aquatic. After copulation, females may cannibilize a smaller male for energy they require to sustain the long gestation period during which they will not eat.

Females undergo a gestation period of six to seven months and are ovoviviparous, giving birth to live young. A single litter usually comprises 20 to 40 offspring. Newborn anacondas measure around 70 to 80 centimeters in length. They receive no parental care and face substantial predation risks during their early stages of life. However, if they survive, they grow rapidly until reaching sexual maturity within a few years.

Ecosystem role:

As apex predators, green anacondas help regulate the populations of prey species in their habitat. By preying on various animals, they contribute to maintaining a balance in the ecosystem, preventing the overpopulation of certain species that could otherwise have negative impacts on vegetation and other fauna. The green anaconda influences the distribution and behavior of other organisms. This can lead to adaptations in prey behavior, such as changes in feeding habits, time spent foraging, or areas frequented, which can have cascading effects on the entire ecosystem.

Although adult anacondas have very few predators, newborn and juvenile anacondas are vulnerable to predation themselves during their early life stages. Various predators, including birds, mammals, and other reptiles, may target newborn and juvenile anacondas as a food source. This predation pressure contributes to the regulation of anaconda populations, thus maintaining the balance of ecosystems.

Threats and conservation

The main threats stem from human activities and encounters. Its large size, coupled with fear, leads to persecution and localized killings. Hydroelectric dams and oil drilling contribute to the destruction of its aquatic habitats in Colombia, Peru, and Venezuela. Some populations in Paraguay are critically endangered due to beach tourism and human impact near the Laguna Blanca reserve. The species is exploited for its skin, used for leather accessories, and the fat is utilized in traditional medicine in parts of Peru and northeastern Brazil and the Guianas.

Due to its large range and occurrence in numerous protected areas within the range, the species is listed as Least Concern. This species can be locally common in some parts of its range. However, there is no data on population trends, so research on population size and trends is needed to better understand the conservation status of this species.

Cultural Significance:

Because of its large size, the green anaconda is persecuted throughout its range due to fear but also predation on pets and livestock. The species faces some human exploitation, with its skin sometimes used for leather accessories and its fat incorporated into traditional medicine in specific regions. Despite local stories of anacondas feeding on humans, there is little evidence supporting such claims. Green anacondas have made their mark in popular culture, often portrayed as colossal creatures capable of consuming adult humans. While these portrayals are common in horror literature and films, it's important to note that there is no verified evidence of this species consuming humans in reality. This is unlike pythons in Asia, which have been implicated in several documented cases of human predation.

One indigenous myth tells the story of Yube, a man who transformed into an anaconda after falling in love with an anaconda woman. He went to live with her in the deep waters, where he discovered a hallucinogenic drink with healing powers and knowledge. One day he decides to leave the water and goes to live with a human wife. One day when looking for fruit, he accidentally steps into the river with one foot, and the anaconda woman and her children crush him and break his bones. Before dying, he sings the song of the nixi pae or ayahuasca. From his body, the yagé vine and chacruna leaf grow which are used in the preperation of ayahuasca.

Recent studies:

In a report from 2023, the golden dorado fish has been observed to follow the green anaconda in a clearwater river in Brazil, in what is probably a “nuclear-follower feeding association”, whereby one organism disturbs the sediment and the other follows and opportunistically feeds on any released food-items. While it is often thought that anacondas don't climb trees due to their heavy build, a report from 2017 mentions arboreal behavior of three anacondas in Ecuador which were found about 10 meters up in the trees. These were all small to medium in size, the reason for this arboreal behavior remains unknown.
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