APPEARANCE

Revered by Amazon Indians and Hollywood film makers alike, the idea of the anaconda grasps our collective imagination, just as its giant muscular body coils around prey.



The quintessential predator lurks in dark unseen crannies of the unconscious to snare our thoughts when we least expect. It is an icon of the Amazon, but we do not see the anaconda on the sides of cereal boxes. Maybe this has to do with a cultural aversion to snakes in general, magnified in the world's largest snake.



Considerable controversy surrounds the maximum size of the anaconda. According to Encarta, "The common anaconda is the longest snake in the western hemisphere and the heaviest snake in the world; on average, a large adult may be 6 m (20 ft) long and weigh 107 kg (235 lb)." According to the Guinness Book of Records, it's the world's second longest snake (28 feet, compared with the reticuated python at 35 feet) but by far the heaviest.



Reports of anacondas in excess of 30 feet are open to some dispute although it seems plausible (and exciting!) that longer specimens do exist.



As in most areas of biology, the common name hides a rather messy taxonomy as there are three or four different species also called by the name of "anaconda". The one most often featured in documentaries and fiction is the biggest species, the green anaconda (Eunectes murinus).



A full grown adult anaconda is a magnificent creature, a writhing mass of muscle, its smooth scales glistening shades of green and brown with black oval oval spots alternating in two rows along the back. The white underside is spotted black.



The body of the anaconda is very muscular, in keeping with its role as a constrictor, while its eyes and nostrils are at the top of the head, enabling it to remain submerged while looking out for land-based prey. Bulges on either side of the head betray the presence of powerful jaw muscles, used to grab and swallow its food.



HABITAT AND DISTRIBUTION

Considering the anaconda's fame, it is surprising that the first scientific field studies were not made until the early 1990s.



Few details are known about the anaconda's geographic distribution. The green anaconda is restricted to tropical South America, in Brazil, northern Bolivia, Colombia, northeast Peru, and in Venezuela, and also in Guyana and Trinidad.



The yellow anaconda (E. notaeus) lives further south to Argentina.



Anacondas live a semi-aquatic life, spending much of their time submerged in water, where they can spend hours at a time before needing to come up for air. Slow-moving rivers, flooded forest and swamps are their favored habitat.



Given their secretive habits and excellent camouflage, it's rare to see anacondas in the wild. However, when cold winds blow northward during the friagem, cooling the air and water, the snakes like to bask out in the open, soaking up the warmth of the sun.



FEEDING AND DIET

Few animals are a match for a full grown anaconda. Items on the anaconda's menu include capybaras, agoutis, tapir, peccaries, large birds, and other reptiles such as caiman.



According to John Kricher (1997: 208) the anaconda is the only natural predator of the jaguar, Amazonia's largest mammalian predator.



Contrary to popular myth, anacondas do not routinely prey on people. Attacks are known, but there are no confirmed reports of actual human deaths due to anacondas.



Photographs purporting to show human victims of an anaconda attack are undoutedly fakes. What is certain is that a full-grown anaconda is a formidable predator, and as such plays its part in the ecosystem, helping to control numbers of prey animals.



The anaconda is a constrictor and lacks poison fangs. However, it does have impressive rows of backward facing teeth (Click for picture) that enable it to ratchet the prey into the gullet once the struggle is over. And the struggle is quick.



Lying in wait, usually submerged in water, the anaconda's ambush is lightning fast. First, the anaconda grabs the prey in vice-like jaws, equipped with powerful muscles. Several coils are simultaneously thrown around the prey whose futile struggles only stimulate the snake to tighten its grip. With each exhalation of the prey, the anaconda tightens its coils until the animal is unable to breathe. Usually the fight is over before this as the anaconda pulls the victim underwater, drowning it first.



Like all snakes, a loose ligament connecting the lower and upper jaw enables the anaconda to detach the lower jaw and so swallow prey that exceeds its own body diameter. (Imagine eating a burger two feet across!) Due to its slow metabolism, an anaconda can go a long time between meals. A large animal may keep it going several months. One anaconda in captivity lived for two years without eating.



BREEDING

Most reptiles are egglaying, but anacondas, like a few other snakes are viviparous, they give birth to live young, often several dozen at a time.



During breeding season, anacondas collect in large groups in which males compete for females. The female emits a scent that males find irresistible. She remains in one location, attracting males over a large area, over several weeks. The males flick out their tongues to pick up the chemical emitted by the female.



Many males cluster around the female, culminating in a so-called "breeding ball" in which up to a dozen males coil around the female, competing among each other for the privilege of mating. Mating may take place without such breeding balls, but they seem to ensure that only the largest males will mate.



The bigger female is more powerful than the male, and may be the final arbiter, making her own choice. This courtship phase may last one or two months, and mating takes place early in the rainy season from March to June and most often occurs under water.



The male has a pair of spur-like scales on his underside, which he uses to scratch the female during mating. This stimulates the female to raise her cloacal region, enabling the male to maneuver his cloaca towards the female. During the process, the male and female intertwine in a living, writhing knot.



About six months after mating, about 20 to 40 live young are born. Up to 100 young may be born. The baby snakes are 2 to 3 feet, and at this stage are vulnerable to all kinds of predators such as birds and cats.



In a few years, the young grow big enough to deter predators and reach sexual maturity in five or six years, growing 500 times heavier than their birth weight. In the wild, anacondas may live to 30 years of age.



CONSERVATION

Due to the difficulty of studying anacondas in their natural habitat, conservationists have a hard time pinning down their numbers. All South American countries prohibit trade in skins or live animals, although some South American countries allow anacondas to be exported for scientific research or to zoos, but commercial trade is prohibited because the species is listed on CITES, Appendix II.



The anaconda faces threats directly from people who fear that it is a man-eater, although attacks are rare, and according to Rivas (1999) there are no confirmed reports of human deaths from anacondas.



In other cases, the anaconda is hunted for its skin, either for leather or decoration. (Photos of snake skins)



Habitat loss is another major threat for anacondas. Although they are adaptable animals, adults require sizable prey and suitable habitat. As wetlands are drained, forests are cleared and rivers are dammed, less and less food and habitat is available for anacondas.



MYTHOLOGY

Some Amazon Indians believe the sinuous rivers are made by a giant snake; an indication that the native people see the similarity of shapes.



Beder Chavez (a naturalist guide in the Peruvian Amazon) writes:

