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Anacondas are three species of aquatic boa inhabiting the swamps and rivers of the dense forests of tropical South America.

Two species are well-known:

• The Green Anaconda (Eunectes murinus), which has been reported at up to 10 metres (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 girth of more than 30 cm (11.8 inches) in diameter. Females are larger than males. These are found mainly in northern South America, in Venezuela, Colombia, Brazil, northern Bolivia, northeast Peru, Guyana, and Trinidad.

• The Yellow Anaconda (Eunectes notaeus), which reaches a relatively smaller maximum length of 3 metres (9.8 feet). These live further south in Bolivia, Paraguay, Uruguay, western Brazil, and northeast Argentina.

The third lesser known species is:

• The Dark-Spotted or Deschauense's Anaconda (Eunectes deschauenseei) found in northeast Brazil.

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. The anaconda combines an arboreal with an aquatic life, and feeds chiefly upon birds and mammals, 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.

Like almost all boas, anacondas give birth to live young.

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.

Giant Anacondas

The biggest known anacondas are about 10.6 meters (35 feet) long, but reports of much larger snakes have occasionally been made.

One notable account was reported by adventurer Percy Fawcett. In 1906, he wrote, he shot and wounded an Anaconda in South America. Fawcett reported the snake measured some 18.9 meters (62 feet) from snout to tail.

Once publicized, Fawcett’s account of a giant snake was widely ridiculed. Fawcett insisted his account was truthful and accurate. Bernard Heuvelmans, for one, thought this ridicule unfair, arguing that Fawcett generally related things truthfully and reliably. Furthermore, Heuvelmans noted, 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. 6 meters (20 feet) in length was once the widely-accepted maximum size.

Sources

• Bernard Heuvelmans, ‘’On The Track Of Unknown Animals’’, Hill and Wang, 1958

See also:

• Anaconda (movie)
• Anaconda, Montana (named for the Anaconda Copper Mining Company, whose company town it was)
• Anaconda installer, the Red Hat Linux and Fedora Core installation program