Green Anaconda
The Largest Snake In The World

Widely considered to be the largest snake on earth, the green anaconda ( Eunectes Murinus) has become an object of real exaggeration, specifically in respect of its size as well as behaviour towards people.

The Columbia Encyclopedia reports that the anaconda may reach 7.9 m in length and 90 cm in girth. (Ref. 1)

Green Anaconda Green Anaconda
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The anaconda is a semi aquatic boa (also sometimes called a water boa) that lives in swamps and rivers in South America. It is a non-venomous constrictor (it kills other animals by way of constriction - see the explanation above) and it swallows its prey whole. (Ref. 2)

Quite often though the prey die by drowning rather than suffocation. (Ref. 3)

This snake is a good climber and can often be found hanging on tree branches over tropical streams. (Ref. 4)

The green anaconda, like all other snakes, has a very slow rate of food digestion. It can live for a year after eating a big meal without having to eat more! (Ref. 5)

It has been recently found that female green anacondas are much larger than male ones. (Ref. 6)

The female anaconda delivers its young alive (as compared to some other snakes which lay eggs - for example, pythons). It can give birth to as many as fifty, sixty or even seventy young ones at a time, which can be 30 or more inches long. (Ref. 7)

Scarcity of Knowledge about Anacondas

In spite of so much popular interest in the green anaconda, so far I have only heard of one recent field study carried out in the Venezuelan region of Llanos, to find out more about the biology of this snake.

Dr. Jesus A. Rivas, among the group of other scientists, has been doing research on the green anaconda (Eunectes Murinus) in his native Venezuela since 1992 and has been regularly reporting on his findings in the international media.

From the moment an anaconda is born till adulthood, its biomass increases by 500 times which is much higher than in any other species of snakes. (Ref. 8)

John Thorbjarnarson , who worked with Jesus A. Rivas (see the sidebar) on the anaconda research project, describes it as "... a striking creature to behold. Its head, with a prominent red stripe, is dwarfed in comparison to the improbable bulk of the body, with its glossy skin and bold, black markings on an olive-yellow background." (Ref. 9)

He refers to these snakes as "secretive", "shy, retiring creatures" which are often difficult to detect even by a practiced eye.

As a result of the above mentioned project, the researchers found out some very interesting facts about green anacondas.

Below are some quotes about their discoveries:

"Much to our surprise, the anacondas were quite mobile and had well-defined "home ranges," that is, areas with which they were intimately familiar. The snakes would move around these home ranges, with certain areas being preferred during certain times of the year, mostly depending on water level. During the dry season, many of the males become especially mobile as they search for receptive females.

Like many snakes, anacondas can go for long periods without eating, but at times large snakes can be seen literally bulging with a freshly swallowed meal. ... anacondas do have a varied diet, consuming small mammals, birds, turtles, and even large prey such as caiman and deer.

We are also learning that anacondas have a fascinating mating system. ... in March of our first year we began finding some of the large females grouped with several smaller males. Males appear to seek out females during the late dry season, and, when more than one male finds the same female, these "mating balls" can ensue.

In subsequent years we have found numerous groups of snakes intertwined in gorgonlike masses, usually while partially buried in mud or under moist mats or grass around the edges of drying pools. These mating balls of anacondas can be quite impressive; one photographed female was completely enwrapped by seven males." (Ref. 10)

J. A. Rivas tells us that there is a presence of cannibalism among the anacondas. During all the occasions of cannibalism recorded by his research team, it was (larger) female anacondas eating (smaller) male ones. He then concludes that "after mating pregnant females do not eat for seven months. It is possible that breeding females eat their mating partners in order to help them survive the long fast associated with pregnancy." (Ref. 11)

Most Amazing Fact About Anacondas

What amazes me most about anacondas is the sheer size of some of their victims such as deer for example. They can also quickly regurgitate all that they have swallowed if they are disturbed or frightened though!

J. A. Rivas also reports that, though anacondas are not typical "man-eaters", they nonetheless can attack human beings.

He states that on a couple of occasions two of his field assistants were unsuccessfully attacked by anacondas, possibly because of a high exposure of these researchers to the anacondas they were tracking. (Ref. 12)

P. R. Cutright cites several recorded instances of anacondas attacking humans but refers to them as only "slight evidence".

This is what he thinks about it:

". the anaconda does not make a practice of attacking man; it prefers animals with fewer clothes. However, the fact that it generally shies away from human beings at meal time does not mean that it is incapable of swallowing a man.

A twenty- or twenty-five-foot anaconda could, beyond any reasonable doubt, swallow a medium-sized man provided the shoulders were not too broad or the waist line too pronounced, and there would be no question as to its ability to engulf a child.

The human body, when prone or supine, has just the stream-line contour that should appeal to one of these huge water-inhabiting serpents, and there are no spurs, antlers, tusks, or other pronounced excrescences which, in other animals, hinder the snake from taking its dinner in toto.

When one considers these facts it is difficult to understand just why more of the South American natives are not attacked.

It may be that the anaconda judges the size of a prospective animal in terms of its height. If that be true, a man would appear much larger than any of the other animals, and it would, accordingly, leave him alone.

Then, too, in an environment where food is common enough, it is logical to suppose that the anaconda would rather swallow, with ease, two or three fairly small animals than exert itself to the limit with a single, huge one.

If it were sufficiently hungry, though, it might attack any animal it was capable of ingesting.

Many of the swallowing feats attributed to this serpent--swallowing horses and cattle, for example--are manifestly exaggerations.

It could, and probably does, swallow peccaries and capybaras, and possibly young tapirs. It likes chickens and eats them--spurs, feathers, comb and all--whenever the opportunity presents itself." (Ref. 13)

Conservation Status of Green Anaconda

J. A. Rivas warns us that "due to skin trade and habitat degradation its [anaconda's] numbers have declined in places where they are not protected" and that further action is required to understand this species better and develop guidelines for its protection and management. (Ref. 14)

Just like for the jaguar, tropical frogs (and specifically poison dart frogs) and other rainforest animals, the recent high rates of rainforest destruction, in particular in South America where the anaconda lives, do not help this snake either.

As of this moment, the green anaconda is listed in Appendix II of CITES. This means that all the commercial trade in this species is prohibited in the South American countries that it inhabits, with the exception of exports for zoos and research purposes.

It looks like the green anaconda is falling victim to the human prejudice and ignorance as well. Whereas I can personally understand why it instils fear into people who encounter this enormous snake and who are not sure how to deal with such encounters, it is certainly no reason to kill it every time they see it.

As Heidi Ridgley reiterates, thousands of anacondas are still killed every year either out of fear or to sell their skins for a profit. (Ref. 15)

There are local efforts to protect the green anaconda, alongside many other species of animals, by establishing reserves throughout South American countries. Some of such reserves are, for example, Cristalino State Park (ref. 16) and a number of reserves in the Llanos area of Venezuela (ref. 17).

Though the current state of anacondas' existence does not necessarily make them endangered animals as such, there is a clear need for their further protection.

Written by:     Irina Bright of

Publication Date:     November 2007

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