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Green Anacondas

About AquaFacts: AquaFacts are a resource for students who are looking for information on the animals at the Aquarium or other Aquarium-related topics. Here, we’ve compiled some of the most frequently asked questions that we’ve received about anacondas. The answers come from our biologists and from reputable sources that we reference at the end of this page. If you have a question about anacondas that’s not addressed in this page or the references below, please feel free to email our librarian.

Anaconda

Questions & Answers

Where do anacondas live?

They live throughout tropical South America, mostly east of the Andes through the Amazon and Orinoco river basins, as well as in Colombia, Venezuela, Northern Bolivia and South Central Brazil. Green anacondas are often found in swamps and slow moving rivers. They will hang from tree branches or along riverbanks to sun themselves and ambush prey.

anaconda-in-tree.jpganaconda-in-water.jpg

What do anacondas eat?

They eat different types of mammals, fishes, caimans, birds and turtles. The snakes at the Vancouver Aquarium primarily get a diet of rabbits, rats and mice.

How do they find their food?

Being a powerful constrictor, the anaconda subdues its prey by coiling around their bodies. The ambushed prey's death results usually by loss of circulation, but sometimes from suffocation or a broken spine or neck.

How do they reproduce?

Like all snakes, green anacondas reproduce sexually and use internal fertilization. Mating typically occurs between April and May. During breeding, the anacondas often cluster in a breeding ball that may consist of 2 - 12 males coiled around one female. The snakes can stay like this for two to four weeks. Green anacondas produce eggs, but the eggs hatch inside the female’s body. The young are then born as miniature snakes. Scientists call this type of birthing ovoviviparous; “ovo” for egg, “vivi” for live and “parous” for birth. Females can give birth from four to 82 young. The longer the female is, the longer the litter size will be. First time mothers have average litter sizes of 10 - 30 young.

Are anacondas dangerous?

To humans, not really: There are some documented attacks by green anacondas on humans, but they are few and far between. This may be because few people live in places where anacondas are common. There are many myths and stories that depict anacondas as ‘man-eaters’ but anacondas are not ‘man-eaters’ by nature. They are generalists and will take any prey they can subdue and swallow. Large anacondas can capture prey as big as adult capybaras (giant rodents), adult white-tailed deer and full-grown spectacled caimans. These are the same size as a small human (weighing up to 55 kg).

Are anacondas endangered?

Not really, but the anaconda belongs to the Boidae (Boa) family of snakes and these species are listed in the CITES II appendix. The CITES II appendix lists species which might become endangered if trade is not controlled. Trade in anacondas is prohibited in most South American countries although some are still exported for zoos, research or the pet industry. Few people take anacondas as pets because they grow quite big and are potentially aggressive, although anaconda skins are still traded illegally. These large snakes have very few natural predators because of their size. The main causes of population decline are poaching and habitat destruction.

Boas vs. Pythons

Boas and pythons are included in the Boidae family, but pythons belong to a subfamily called Pythoninae. The main difference between boas and pythons has to do with their offspring. Boas are ovoviviparous, meaning that the eggs hatch inside the female and the babies are born live. The membrane surrounding the young breaks during birth and allows them to immediately move away from the mother. Pythons are oviparous, meaning that a thin parchment-like shell surrounds the babies. The female lays the eggs and usually incubates them by wrapping her body around the eggs.

anaconda-python.jpganaconda-boa.jpg

How old are the anacondas in the Amazon Gallery?

The male green anaconda will turn 20 this year. The female anaconda is estimated to be about nine years old this year and is a rescue animal from Milwaukee, United States.



Facts & References

Key Facts

  • The average life-span ranges from 10 - 30 years.
  • Adults on average weight up to 68-180 kg.
  • Average length for females (who usually have a much larger mass and length than males) is around six meters. Average length for males is around three meters.
  • Males reach sexual maturity at around 18 months of age (two meters long). Females mature at around three years of age (three meters long).
  • The length of pregnancy (gestation period) for an anaconda is between six and seven months.

Did You Know?

  • The green anaconda is considered the largest snake in the world: it received this title because of its weight, rather than its length.
  • Sometimes called the "water boa", green anacondas are the most aquatic of all the boas: Eunectes, from their scientific name, means "good swimmer".
  • Anacondas are born with all the skills they need for survival, including the ability to swim.
  • Adult anacondas don't care for their young and, if given the opportunity, will even eat them.

References

  1. Bauchot, Roland (ed.) 1994. Snakes, a Natural History. New York. Sterling Publishing Co., Inc.
  2. Ernst, Carl H., and Zug, George R. 1996. Snakes in Question. Washington: Smithsonian Institution Press.
  3. Rivas, J.A., Owens R.Y. and P.P. Calle. 2001. “Eunectes murinus: Juvenile predation.” Herpetological Review. 32(2): 107-108.
  4. Rivas, J.A. 1998. “Predatory attack of a green anaconda (Eunectes murinus) on an adult human”. Herpetological Natural History 6(2): 157-159.
  5. http://www.cites.org/eng/resources/species.html

  6. http://animaldiversity.ummz.umich.edu/accounts/Eunectes_murinus/

Permission is granted by the Vancouver Aquarium Marine Science Centre for classroom teachers to make copies for non-commercial use. This permission does not extend to copying for promotional purposes, creating new collective works, or resale.

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