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Anaconda: green and giant

The green anaconda (Eunectes murinus) is a species of constrictor snake of the Boidae family.

It is considered the largest of all snakes of this family living in the Amazon basin, and even in the entire American continent, and the longest snake in the world. It is also on the list of the largest snakes on the planet, competing with the Asian python reticulata, famous for its weight (up to 250 kg) and its length (up to 8 m).

anaconda near the beni river in bolivia
Anaconda near the Beni river in Bolivia. Source: Phil Whitehouse Some rights reserved

But the green anaconda is longer, as the female can reach a total length of 10 m, although it is less bulky than the python reticulata, generally weighing between 35 and 85 kg, although specimens weighing 97 kg have been reported.

Anaconda 2,4 mts. (Eunectes murinus), Parque del Este, Caracas LOW
Anaconda 2,4 mts. (Eunectes murinus), Parque del Este, Caracas Source: Don Perucho Some rights reserved

The green anaconda is the largest among other species of the genus Eunectes: E. beniensis, E.deschauenseei, E. notoeus (Milord 2012).

These large snakes, the green anaconda and several species of python (the python reticulata and the silk python), are generally hunted because of the fear they instill, often exaggerated, which has caused their conservation to reach the level of endangered species in some regions.

However, these large snakes are not venomous; they kill by suffocating their prey. And they only attack humans in self-defense, when provoked.

Where does the anaconda live? (habitat)

The green anaconda is aquatic or semi-aquatic, diurnal or nocturnal, and can live both in water and in trees.

It can be completely submerged for 10 minutes, and then bring its nostrils to the surface.

For hunting, it prefers lentic water bodies, from sea level to 1,000 m above sea level.

It dives into the water, keeping its nostrils out, on the lookout for a thirsty animal approaching to drink.

Distribution of the Anaconda (Eunectes murinus) in South America
Source: Gossipguy[CC BY-SA 4.0].

The anaconda is a species endemic to the Amazon basin, and is widely distributed in the Amazonian regions of Colombia, Venezuela, Bolivia, Ecuador, Peru, Brazil, Guyana, French Guiana, Suriname. It is also found in some Caribbean islands.

What does the green anaconda eat? (food)

It is, together with the Orinoco crocodile(Crocodylus intermedius), a major predator of some of the animals of the bush, such as the capybara, chiguiro or capybara(Hydrochoerus hydrochaeris). Specialists point out that the green anaconda rarely lives more than ten years.

Sexual Disformity

The green anaconda is a notable case of sexual dimorphism, since the female specimen is much larger and heavier than the male, which reaches a length of 4 to 5 m, and a weight that hardly exceeds 35 kg.

Description of the species

The skin of the green anaconda is dark green, dotted with black and ochre patterns or spots on the sides or flanks. The color becomes lighter in the belly area.

The terminal part of the tail has yellow and black patterns, which generally differ from one specimen to another.

The large snout is covered by six thick scales, three on each side, which characterizes the genus Eunectes and differentiates them from snakes of the genus boa.

The entire body is covered with scales, except for the caudal part, near the cloacal area. There appear a sort of spurs, or remains of their lost locomotive extremities.

The tail has a particular design pattern, which is an exclusive drawing for each specimen, as if it were a human fingerprint.

Green Anaconda in Trivandrum Zoo Source: Mithun.M.Das[CC BY-SA 4.0].

On the other hand, the anaconda’s head is triangular, large but narrow.

The eyes appear at the top of the head, as well as the nostrils. This circumstance favors breathing and its perception capacity.

A skilled hunter

For hunting, it uses the olfactory receptors on its large, black, forked tongue. It has loreal pits and dilatable pupils, making it easy to locate prey in the dark.

The anaconda, despite its length and weight, moves with great agility. However, its movements are relatively slow, and it moves at a maximum speed of 11.3 km/hour.

To hunt, it moves its tongue, which is its olfactory organ, connected to Jacobsos’ organ, located in the upper part of the mouth to perceive odoriferous particles, detect sounds, as well as the movement of prey by means of vibrations in the substrate (Place and Abramson 2006).

Thermal vision

In addition, they can detect the presence of nearby animals only by the heat they radiate, distinguishing the distance and size of the possible prey.

Before combat or when hunting prey, it dives into the water and curls its body into a ball, protecting its head, getting ready to attack. It then excretes a substance with an unpleasant odor.

Anaconda on the prowl Source:: Daniel10ortegaven [CC BY-SA 3.0]

Its large build, size and weight give it a powerful strength and resistance that allows it to squeeze its prey until it suffocates it, no matter how big it is. This is how it proceeds with capybaras, deer, tapirs, monkeys, etc. It does so in a few seconds.

When on land, it climbs trees to hunt its prey. He coils her up with his body, carries her into the water and suffocates her, preventing her from breathing. It opens its mouth, unhinging its jaws, and swallows the prey whole, helping itself with its four rows of teeth, starting at the head to avoid getting stuck.

Anaconda, Pedda Poda, Port Natal Python, Rattlesnake, Rattlesnake Black Variety, and Cobra de Capello from A history of the earth and animated nature (1820) by Oli
Anaconda, Pedda Poda, Port Natal Python, Rattlesnake, Rattlesnake Black Variety and Capello’s Cobra from A History of Animated Earth and Nature (1820) by Oli Source: Rawpixel Ltd Some rights reserved

To swallow their prey and digest it, their esophagus and stomach are very thin, but flexible and resistant to withstand the action of gastric juices that break down the bones of their victims.

The digestion of a large prey can last several weeks, remaining inactive in the soil, or resting in the water. It has a slow digestion, and does not need to eat daily. It can even last without eating for up to 8 months.

Anaconda devours a capybara or chigüire(Hydrochoerus hydrochaeris). Exhibited at the Senckenberg Museum in Frankfurt-sur-le-Main. Source: Eva Kröcher(Eva K.) CC-BY-SA 2.5

Perhaps, in the jungle, the jaguar(Phantera onca) is its only predator.

Sometimes she is self-deprecating. It happens when it stops, and it must feed in the middle of its inactivity and the season is dry.

Anaconda reproduction

Female anacondas reach sexual maturity between 3 and 5 years of age.

They attract males by means of an olfactory signal.

Several males come to her call and court her for weeks, competing for the female’s favor.

anaconda and woman
Anaconda and woman Source: ingridgott Some rights reserved

In the last week, as many as thirteen males have been counted, curling in a ball around the female, vying to reach her cloaca.

The female anaconda is polyandrous, that is, a female copulates to reproduce with several males.

Since she is bigger than the male, she submits him, choosing the one she prefers, which is usually the biggest and strongest.

We found this anaconda gliding through the marshes (an hour's walk from the Beni River).
We found this anaconda gliding through the marshes (an hour’s walk from the Beni River). Source: Phil Whitehouse Some rights reserved

The male moves his tongue and his spurs become erect.

He rubs against it. The male spurs stimulate the caudal region of the female. Copulation is completed when the female raises her cloaca towards the male.

Then, the male embraces her tightly, squeezing her tail and lower body around her. The tails of both curl, and the cloacae come into contact, producing insemination. The gestation period lasts seven months, and they are oviparous.

Uses of anaconda parts

The meat of the anaconda is edible for many indigenous peoples. Its leather is used to make leather goods. Such as wallets, purses, handbags, belts. Its use, however, is greater in traditional folk medicine.

Butter from large snakes, such as anaconda and boa, are used as an effective medicine to reduce inflammations, as pointed out by clinical evidence (Cabrera- Pachacama 2018, Ferreira et al 2014, Alves et al 2013a, Alves et al 2013b ), and as a wound healer (Souza et al 2017, Silva 2008).

For this reason, butter is one of the most sold products in the markets of Amazonian cities (Pinto and Maduro 2002). It is also recommended for rheumatism and asthma (Alves and Rosa 2007).

An endangered species

Its usefulness, especially therapeutic, is a threat to its conservation status, although it has hardly been evaluated.

In several red lists of reptiles, such as that of Ecuador, the anaconda appears as an “endangered species”.

Their situation is aggravated by the fact that they are hunted for their meat and skin, and especially for some of their organs to be used as medicines.

The destruction of their habitat and hunting by ranchers is another contributing factor to their conservation.

An Anaconda ”Eunectes murinus ” found caught in fishing nets and brought back to the Lodge in Requena, Loreto, Peru Source: Dave Lonsdale (CC-by-2.0)

They kill her because they see her as a threat to their herds. Thus, ranchers and settlers altered many parts where the anaconda used to live: they dried up the most fragile marshes and morichales, causing the alteration of the ecosystem of the species’ habitat, proceeding in a different way than the Amazonian indigenous people do.

Myths of the anaconda

Ophidians are among the animals that have produced the greatest amazement to mankind throughout history.

Their unusual appearance, their speed, the deadly poison they inoculate, their forked tongue, their way of living in the shadows, hiding under stones or dry leaves, or climbing tree branches, the surprise they cause and the skill with which they act.

The myth of the man-anaconda

The fascination they produce has turned them into frequent symbols in many indigenous cosmogonies, particularly in the Amazon basin, where they are associated with a supernatural being called “guíos” in some ethnic groups.

Guidance is the transformation of a human into an animal.

Some indigenous legends relate that a man was offended in his dignity by his wife, who had made denigrating comments about him with other women.

To fulfill his revenge, he was transformed into an animal, taking the form of an anaconda that lived in the morichales.

When his wife went to look for the fruits of the moriche or buriti (Mauritia flexuosa), a palm that grows in flood zones, the anaconda man trapped her and penetrated her body repeatedly until she was exhausted, and then took her with him (Parra-Dusán, Amparo Rodríguez 2005: 111).

Influence of anacondas in art

The fear aroused by large ophidians, which remind us of death, has attracted the attention of novelists, storytellers, poets, painters and film directors.

The Uruguayan writer Horacio Quiroga (1878-1937), one of the masters of the Latin American short story, dedicated two of his most famous stories to it: “Anaconda” and “The Return of Anaconda”, in which an anaconda is the protagonist.

Another writer, Mathias Bradley, wrote a novel “The terror of the Amazon Rainforest”, also directly related to a group of anacondas that escape from a research center in the middle of the Amazon rainforest, and become monstrous when they come into contact with a toxic chemical substance.

Another novelist, this time Peruvian, Arturo Hernández, in his novel Sangama, written in 1942, recounts the combat between an anaconda, the Yacumama, and a jaguar, in which the snake wraps the feline’s body and takes it to the water to drown it.

Anaconda: the movie

Modern cinema has made the anaconda an object of horror in several blockbuster films, such as the Anaconda series films of the late 1990s.

Although anacondas and boas have been portrayed with a negative and scary image, specialists in herpetology (the study of reptiles and amphibians) show us shy animals that shy away from humans and only attack them if they feel they are being attacked.

The remote ancestors of anacondas and boas

Snakes are descended from lizards, as they are basically large lizards that have lost their legs.

Polyoutis[CC BY-SA 4.0] Anaconda and Squamata skeletons.jpg

About 140 million years ago, saurians began to dig the earth. To do so, they had to adapt their bodies: they developed a transparent scale like a fixed eyelid to protect their eyes, and a horny skin in the form of scales, with a hard, rigid and impermeable texture similar to human fingernails.

In that transit they lost their external ear, in a certain way their sense of hearing. They do not have ears or eardrums, but they pick up sounds and vibrations on the ground, thanks to two bones in their skull, the mandible and the columella, which pick up sounds and transmit them to the inner ear.

The scales they developed were very convenient for body protection, but became “uncomfortable” as they grew and had to be changed.

That’s why they do it every so often, and become irritable during the process. Snakes used to resemble lizards: they had four legs and two lungs, and began to differentiate 130 to 140 million years ago.

Primitive and evolved snakes

They formed, then, two groups: primitive snakes and evolved snakes.

The primitive ones were represented by boas, including anacondas, and pythons, which retained their two original lungs and tiny traces of their legs on their skeletons.

The evolved ones have only one lung, and are represented by two types: non-venomous snakes (called “snakes”) and venomous snakes, which are vipers, rattlesnakes and cobras.

“Snake” and “viper” are thus antonymous terms.

Snakes (non-venomous) and vipers (venomous)

Venomous snakes generally have a triangular head, a slit under each eye known as a loreal pit, and their scales are opaque, although they may be colored.

The non-venomous ones, on the other hand, usually have a flattened head, lack a loreal seta and their scales are shiny. As can be seen, anacondas do not comply with these rules.

Titanoboa or Giant Anaconda?

Some specialists name it as titanoboa, specifically Titanoboa cerrejonensis.According to the reconstruction of fossil remains found in a coal mine in Cerrejón, in what is now the department of La Goajira, Colombia, this species may have measured more than 13 meters long and weighed 1,135 kg.

They place it in the Paleocene, in South America, some 60 to 58 million years ago.

Using this fossil, an animated reconstruction was made with metal parts, 14 meters long and weighing 90 kg, which was exhibited at Grand Central Station, New York, in 2012, to promote a TV documentary, “Titanoboa, The Monster Snake”, presented by the Smithsonian Channel on April 1, 2012 (Mead, Bloch and Moreno-Bernal 2013).

Lalikilpará, Anaconda over 50 meters long
Lalikilpará, Anaconda of more than 50 meters. The anaconda Lalikilpará, a character from a legend of the Tamanaco Indians, wanted to flood the earth to wipe out mankind. This representation was made at the Bicentennial Parade “Independencia para Siempre” held in Caracas on July 30, 2011. Source: Luigino Bracci Some rights reserved

Boas and anacondas

Anacondas and boas belong to the Boidae family. The name boa comes from the Latin term “boa”, which means “ox-killer”.

Many interchangeably call both genera, Eunectes and Constrictor, as if they were one and the same, and use the same terms to designate them. But there are significant differences between the two.

The Boa constrictor constrictor (red-tailed boa) is smaller than Eunectes murinus (green anaconda), both in length and weight. The boa has a labial pouch, while the anaconda has a loreal or thermoreceptor pouch.

Both detect temperature changes in the environment, especially in potential prey, but the loreal seedeater is more complex and complete, detecting changes down to 0.0001 °C, and both visible light (as we do) and infrared radiation.

Both are good swimmers, but the anaconda’s aquatic vocation is greater than that of the boa.

Red-tailed boa constrictor in Guyana. Source: Embreus (CC by 2.0)

The description of the characteristics of boas is practically similar to those of anacondas: forked tongue, a highly developed sense of smell (using the tongue to smell the air and detect chemical substances), they have a less developed sense of hearing (they lack an external ear and eardrum).

They differ basically in length, weight, body color and tail design patterns, but both share their habitat (one more in the water, the anaconda), their primary centers of origin and even the prey they eat and their predators.

The most representative among other boa constrictors: B. c. amarale, B. c. c. Imperator, B. c. longicauda, B. c. melanogaster, B. c. occidentalis, is the red-tailed boa(Boa constrictor constrictor), distributed from northern Mexico to Argentina. It lives from sea level to 1,000 meters above sea level.

Description of boas.

The B.c. constrictor is the largest of the boas, reaching up to 4 m in length in the wild, well characterized by the bright red color at the end of its tail.

Along the body it has dark spots on a light beige background.

Its belly is cream colored, with black dots.

Its head is wide and, on each side, behind the eyes, it shows a dark stripe. His eyes are round.

It has numerous small teeth.

It has small scales on the top of the head and on the sides of the muzzle.

Boa constrictor (Jibóia). Source: Leandro Avelar[CC BY-SA 4.0].

On the back of the body and on the tail it has black, yellow and red stripes or rings.

It has vestigial organs in the pelvic girdle as nails on each side of the cloaca.

Females are larger than males, and are said to live up to 20 years in the wild and up to 30 years in captivity.

Behavior of boas

The red-tailed boa, or matacaballos (Ecuador), or patacona (Colombia), is a solitary animal with nocturnal habits.

It spends most of its time suspended in the branches of trees or inside a hollow trunk or in an abandoned burrow of large nets.

From there it goes out at night to hunt, compensating for its poor eyesight with the help of its thermosensitive scales, to catch lizards, birds in their nests, opossums, bats, rats and other rodents, squirrels.

Boa constrictor occidentalis. Taxidermied specimen and skeleton. Source: CHUCAO [CC BY-SA 3.0]

It captures the bats, from the trees, in full flight. It kills its prey by constriction until it suffocates them.

It swallows them whole, from the head. It lasts for at least a week, depending on the size of the prey.

It is preyed upon, in turn, by felines and birds of prey. It is threatened by habitat destruction, overhunting (for its skin and medicinal lard) and illegal trade for use as a pet.

For this reason it is also a species bred in captivity. It is not an aggressive animal unless attacked (Pazmiño-Otamendi and Guerra-Correa 2019, Enriquez 1999).


The female attracts males by secreting pheromones. The male passes over the female, pressing her gently, inciting the female to ovulate. The male inserts one of his two hemipenes, or spurs, into the female’s cloaca to deposit his sperm. At four months, after molting, they give birth to 20 to 60 live young, 25 on average, with a length between 30 and 40 cm (Santoyo-Brito 2007).


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