2007 Schools Wikipedia Selection. Related subjects: Insects, Reptiles and Fish

Yellow Anaconda, Eunectes notaeus
Yellow Anaconda, Eunectes notaeus
Scientific classification
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Boidae
Genus: Eunectes
Wagler, 1830

4, see article.

Anacondas (local names: Jibóia and Sucuri) are four species of aquatic boa inhabiting the swamps and rivers of the dense forests of tropical South America. The Yellow Anaconda can be found as far south as Argentina.

There are two possible origins for the word 'anaconda': It is perhaps an alteration of the Sinhalese word 'henakanday', meaning 'whip snake', or alternatively, the Tamil word 'anaikondran', which means 'elephant killer', as early Spanish settlers in South America referred to the anaconda as 'matatoro', or 'bull killer'. It is unclear how the name originated so far from the snake's native habitat; it is likely due to its vague similarity to the large Asian pythons.

Taxonomy and General Characteristics

Two species are well-known:

  • The Green Anaconda ( Eunectes murinus, from the Greek "ευνήκτης, eunectes", meaning "good swimmer"), which has been reported at over 10 meters (32.8 feet) in length (although most are considerably smaller). Although shorter than the longest recorded species, the Reticulated Python, it is considerably heavier. In fact, it is the heaviest snake species in existence. It can weigh 250 kg (551 pounds) and have a diameter of more than 30 cm (11.8 inches). Females are larger than males, averaging 22-26 feet and 12-16 feet respectively. These are found mainly in northern South America, in Venezuela, Colombia, Brazil, Ecuador, northern Bolivia, northeast Peru, Guyana, and the Nariva Swamp in Trinidad where they are known as "Huille" (pronounced Wheel). Although charismatic, very little information was known about the anacondas until 1992 when the first study (and so far the only) was made on the field biology of this species in the Venezuelan llanos by Dr. Jesus Rivas.
Green Anaconda, Eunectes murinus
Green Anaconda, Eunectes murinus
A wild anaconda snake, Amazon basin, Peru.
A wild anaconda snake, Amazon basin, Peru.
An anaconda snake on a tree branch, waiting for its prey above the river, Amazon basin, Peru.
An anaconda snake on a tree branch, waiting for its prey above the river, Amazon basin, Peru.
  • The Yellow Anaconda ( Eunectes notaeus), which reaches a relatively smaller average adult length of 3 metres (9.8 feet). These live further south in Bolivia, Paraguay, Uruguay, western Brazil, and northeast Argentina.

The two lesser known species are:

  • The Dark-Spotted or Deschauense's Anaconda ( Eunectes deschauenseei) found in northeast Brazil.
  • The Bolivian Anaconda ( Eunectes beniensis) found in Bolivia, which was only identified in 2002 by Lutz Dirksen, and is still being studied.

Eunectes murinus (formerly called Boa murina) differs from Boa by the snout being covered with shields instead of small scales, the inner of the three nasal shields being in contact with that of the other side. The general colour is dark olive- brown, with large oval black spots arranged in two alternating rows along the back, and with smaller white-eyed spots along the sides. The belly is whitish, spotted with black spots. The anaconda combines an arboreal with an aquatic life and is active mostly during the night. It lies submerged in the water, with only a small part of its head above the surface, waiting for any suitable prey, or it establishes itself upon the branches of a tree which overhangs the water or the track of game.

The anaconda has a large head and a thick neck. Its eyes and nostrils are positioned on the top of the head, enabling the anaconda to breathe and to see its prey while its stocky body lies submerged under water. The extremely muscular anaconda is a constrictor and is not venomous; however, it still has teeth and powerful jaws that it utilizes to clench onto its prey. It grabs its victim and pulls it underwater, drowning the prey. The anaconda has a cavity called a cloaca which is where the intestinal and genito-urinary tracts empty, with spurs on either side of the cloaca, and a gland which emits a foul-smelling musk.

They typically feed on large rodents, tapirs, capybaras, deer, peccaries, fish, turtles, birds, sheep, dogs and aquatic reptiles like caiman. They have been known to occasionally prey on jaguars and attacks on humans can be confirmed, although this is rare. Younger anacondas feed on mice, rats, chicks, frogs and fish. Most local people kill these snakes on sight, out of the fear that they are man-eaters. In most instances, if an anaconda senses humans in the area, it will retreat in another direction. Human death by anaconda is quite rare. They themselves are preyed by jaguars, large caimans and by other anacondas. A wounded anaconda can also fall prey to piranhas.

Anacondas are usually coiled up in a murky, shallow pool or at the river's edge. They wait to ambush their unsuspecting prey when they come down for a drink. Anacondas bite their prey with their sharp teeth, hold on with their powerful jaws and pull them under water. The victim may drown first or it may be squeezed to death in the anaconda's muscular coils. Anacondas, true to the boa family, constrict their hapless victims to death. The snake squeezes tighter each time its prey breathes out, so the prey cannot breath in again. Suffocation does not take long. Anacondas swallow their prey whole, starting with the head. This is so the legs fold up and the prey goes down smoothly. The Anaconda can swallow prey much bigger than the size of its mouth since its jaw can unhinge and the jaw bones are loosely connected to the skull. While the snake eats, its muscles have wave-like contractions, crushing the prey even further and surging it downward with each bite.

Just about every species of snake on earth has teeth, but the anacondas' teeth are not used for chewing. Most snakes' teeth are used for holding onto their prey, preventing them from escaping. Some snakes have venom in two specially designed, extra long teeth which they use to kill their prey. Anacondas do have teeth, but their bites are neither fatal nor venomous. They rely on their enormous size and power to subdue their victims. It is possible to be bitten by an anaconda, but the bite itself would not be fatal. Like almost all boas, anacondas give birth to live young.

Giant Anacondas

The largest known anaconda measured 10 meters (32.8 feet) long, but unverified reports of much larger snakes have occasionally been made. This is the famous Lamon-Dunn record, named for a geological survey expedition from 1944. The geologists who led the expedition found the gigantic snake by the water of the Orinoco river in East Venezuela. Together with a platoon of soldiers of the Farc they shot the dangerous snake, and with the help of 20 men, carried it out on shore. The anaconda was measured with a special measuring device for geological purposes. Although this is probably the largest verified anaconda account, the animal was unfortunately not weighed because after shooting it, the workers went back to camp for lunch. When they returned, it was apparent that the snake was not dead as it had left and the trails indicated that it swam up the river.

An anaconda of 9 meters can weigh up to about 500 kg (1100 lb). The well-fed ones typically weigh about a hundred kilograms per meter of length. A snake this large can kill a large bull or tapir easily. Zoological research has shown trails of snakes on the dry riverbeds on the llanos in Venezuela that indicate extremely large snakes awaiting discovery, some of them were more than 0.50 m wide. Anacondas, like all large species of boas and pythons, continue to grow throughout their lives. Their growth speed reduces after reaching maturity but these snakes possibly reach 50 or 60 years of age, some maybe 80.

There are some exaggerated reports of early European explorers of the South American jungles seeing giant anacondas up to 60 feet long and some of the native peoples of the South American jungle have reported seeing anacondas up to 50 feet long. No one has caught and measured an anaconda anywhere near that size.

Another apparently exaggerated account was reported by adventurer Percy Fawcett. In 1906, Fawcett wrote that he had shot and wounded an anaconda in South America; he reported the snake measured some 18.9 meters (62 ft) from nose to tail.

Once publicized, Fawcett’s account of the giant snake was widely ridiculed, although he insisted his account was both truthful and accurate. Bernard Heuvelmans came to his defense arguing that Fawcett was generally honest and reliable when relating things. Furthermore, Heuvelmans noted that mainstream experts were repeatedly forced to revise their limits regarding the maximum size of snakes when confronted with specimens that defied the generally-accepted estimates. At one point in time, 6 meters (20 feet) in length was the widely-accepted maximum size of an anaconda. These giant snakes are one of the few that have documented, but not verified, cases of eating people. Given maximum size, it is possible, although likely exceedingly rare. When it sheds, an adult anaconda relieves itself of an average of 2 pounds of skin. An anaconda's skin can stretch up to 30% larger than the original size of the snake.

In captivity

Anacondas have a reputation for bad temperament; that plus the massive size of the green species mean that anacondas are comparatively less popular as pets than other boas, but they are fairly commonly available in the exotic pet trade.

In movies

  • In Swiss Family Robinson, Firtz and Ernst have a run-in with an Anaconda.
  • In the movies Anaconda and its sequel Anacondas: The Hunt for the Blood Orchid the anaconda has the role of a giant man-eating snake. In the first film the anaconda is shown at an exceptionally exaggerated length and girth, clearly far larger than actual anacondas in the wild get. However, in the second film it is shown as a 'super snake', growing up to 70 feet long, supposedly because of the blood orchid. Even with extremely rare and old specimens, an anaconda anywhere near that size has never been recorded. Anacondas on average grow between 16-20.2 feet, but have been rumored to reach between 30 and 40 feet.
  • In Jackass: Number Two, Johnny Knoxville, Ryan Dunn, and Wee Man crawl around in a ball pit, trying to catch two anacondas that were let loose in the pit. Knoxville is bitten several times in the arms.
  • The Discovery Channel series Animal Face-Off featured an episode wherein an Anaconda was pitted against a Jaguar in a computer simulation to determine which animal would win a battle between the two.

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