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The green anaconda ( Eunectes murinus), also known as the giant anaconda, emerald anaconda, common anaconda, common water boa, northern green anaconda, or akayima, is a semi-aquatic Boinae species found in South America and the Caribbean island of Trinidad. It is the largest, heaviest, and one of the longest snakes in the world. Like all boas, it is a venom Constriction. The term "anaconda" often refers to this species, though the term could also apply to other members of the genus Eunectes. Fossils of the snake date back to the Late Pleistocene in the Gruta do Urso locality.
Linnaeus almost certainly chose the scientific name Boa murina based on the original Latin description given by Albertus Seba in 1735: "Serpens testudinea americana, murium insidiator" tortoise-patterned. The Latin adjective murinus ( murina) in this case would mean "of mice" or "connected with mice", understood in context as "preying on mice", and not as "mouse-gray-colored", another possible meaning of Latin murinus, as now often wrongly indicated for E. murinus.
Early English-language sources, such as George Shaw, referred to the Boa murina as the "rat boa". The Penny Cyclopaedia (Vol. 5) entry for boa explained: "The trivial name murina was given to it from being said to lie in wait for mice." Linnaeus described the appearance of the Boa murina in Latin as rufus maculis supra rotundatis reddish-brown and made no reference to a gray coloration. Early descriptions of the green anaconda by different authors variously referred to the general color like brown, glaucous, green, or gray.
Common names for E. murinus include green anaconda, anaconda, common anaconda, and water boa.John M. Mehrtens (1987). 080696460X, Sterling Publishers. 080696460X The word akayima and variants ( okoyimo, okoimo) have been used by the local Kalina people to refer to the green anaconda for centuries before its formal scientific description. The name akayima comes from the local Cariban languages, with akayi meaning "snake" and the suffix -ima describing largeness in a way that elevates the term to a separate category, giving a literal meaning of "The Great Snake".
Several proposals have been made to split a new species or subspecies from the green anaconda ( Eunectes murinus), such as Eunectes gigas (Latreille, 1801), Eunectes barbouri (Dunn and Conant, 1936), and Eunectes akayima (Rivas et al., 2024). These proposed species are now considered synonymous with E. murinus.
It is the largest snake native to the Americas. Although it is slightly shorter than the reticulated python, it is far bulkier. The bulk of a green anaconda is comparable to that of a reticulated python. Reports of anacondas or even longer also exist, but such claims must be regarded with caution, as no specimens of such lengths have ever been deposited in a museum and hard evidence is lacking. (1997). 9780894649950, Krieger Publishing Company. ISBN 9780894649950 The longest and heaviest verified specimen encountered by Dr. Jesús Antonio Rivas, who had examined more than 1,000 anacondas, was a female long and weighing .
In 1937, a specimen shot in Guyana was claimed to have measured long and weighed . (1982). 9780851122359, Guinness Superlatives. ISBN 9780851122359
The color pattern consists of an olive green background overlaid with black blotches along the length of the body. The head is narrow compared to the body, usually with distinctive orange-yellow striping on either side. The eyes are set high on the head, allowing the snake to see out of the water while swimming without exposing its body. The anaconda's jaw bones splay open at the front because they are loosely connected. This allows it to swallow prey larger than the size of its head. The windpipe in its mouth allows it to breathe while swallowing its prey. Its largest internal organ is the liver. The digestion process takes many days to complete. During this time the anaconda behaves very sluggishly.Derek Harvey, Smithsonian Super Nature Encyclopedia, First American Edition, 2012, www.dk.com
Reports without physical proof are considered dubious if from non-scientists, as such individuals may at worst be more interested in promoting themselves or telling a good tale, or at the least may not be sufficiently trained in proper measurement methods. Observational reports of animals which were not captured are even more dubious, as even trained scientists often substantially overestimate the size of anacondas prior to capture. According to the Guinness Book of World Records, this species has been perhaps subject to the most extreme size exaggerations of any living animal. .
Almost all specimens in excess of , including a much-publicized specimen allegedly long, have no voucher specimens including skins or bones.
The skin of one specimen, stretched to , has been preserved in the Instituto Butantan in São Paulo and is reported to have come from an anaconda of in length. While in Colombia in 1978, herpetologist William W. Lamar had an encounter with a large female specimen long, estimated to weigh between . In 1962, W. L. Schurz claimed to have measured a snake in Brazil of with a maximum girth of .
One female, reportedly measuring in length, shot in 1963 in Nariva Swamp, Trinidad, contained a caiman. A specimen of , reportedly with a weight of , was caught at the mouth of the Kassikaityu River in Guyana, having been restrained by 13 local men, and was later air-lifted for a zoo collection in the United States, but died in ill health shortly thereafter. The largest size verified for E. murinus in captivity was for a specimen kept in Pittsburgh Zoo and PPG Aquarium, which grew to a length of by the time she died on July 20, 1960. When this specimen was long, she weighed .
The estimated weight for an anaconda in the range of would be at least . National Geographic has published a weight up to for E. murinus, but this is almost certainly a mere estimation. Weight can vary considerably in large specimens depending on environmental conditions and recent feedings, with Verrill's aforementioned specimen, having been extremely bulky, scaled at , whereas another specimen considered large at , weighed only .
The minimum size of breeding anacondas in a survey of 780 individuals was in snout–vent length, indicating that maximum size attained by anacondas following this pattern would be in snout–vent length. However, most anacondas are captured from the Plain, which is more accessible to humans and has smaller prey available, while the rainforest, which is much less explored and has more plentiful large prey, may be home to larger snakes.
The green anaconda is an apex predator, positioning them at the top of the food chain.
In April 2021, green anacondas were added to Florida list of prohibited nonnative species. eleven green anacondas have been verifiably observed in the wild in Florida, including one juvenile found in the Florida Everglades. The range of these specimens, some of which were able to evade capture, spans from Gainesville to Homestead, Florida - a distance of over . Florida is the only state in the continental United States with suitable habitat for the species.
While individual specimens have been observed or captured in Florida dating back to 2010, there is no known established population. However, the ecological, economic, and safety risks posed by their existence in the state are deemed 'very high' by the Florida Fish and Wildlife Conservation Commission, with the ecological threat reaching the extreme risk level, as introduced anacondas are apex predators, able to compete with Florida's native species.
Anacondas live in swamps, marshes, lagoons, and slow-moving streams and rivers, mainly in the tropical rainforests and seasonally flooded savannas of the Amazon basin and Orinoco basins. They are cumbersome on land, but stealthy and sleek in the water. Their eyes and nasal openings are on top of their heads, allowing them to lie in wait for prey while remaining nearly completely submerged.
In both habitats green anacondas have been found to feed on large prey, usually 14–50% of their own mass. Examples of prey include broad-snouted caimans, spectacled caimans, Caiman yacare, black caimans, smooth-fronted caimans, Jacana jacana, , red-rumped agoutis, Pecari tajacu, South American tapirs, boa constrictors, brown-banded water snakes, Iguana iguana, cryptic golden tegus, scorpion mud turtles, gibba turtles, Arrau turtles, Podocnemis vogli, red side-necked turtles, and Northern pudu. Capybaras are common prey for the green anaconda.
Large prey occasionally cause serious injuries and death. This risk is likely reduced when anacondas can drown the prey.
Many local stories and legends report anacondas feeding on humans, but there is little evidence of this. Cannibalism among green anacondas is known. Most recorded cases involving a larger female consuming a smaller male. Scientists hypothesize several explanations, including the great sexual dimorphism of the species, and a female's need for food after breeding to sustain the long gestation. The nearby male simply provides the opportunistic female a ready source of nutrition.
In southeastern Peru, potential prey of green anacondas include collared peccaries, , brocket deer (brocket deer sp.), , , neotropical otters, , spectacled caiman and . Observations show that green anacondas may climb to the top of trees for prey such as green iguanas and brown-throated sloths, demonstrating the willingness to leave their preferred habitat for prey. Green anacondas may even target domestic prey, including , , cattle, , and wild boar.
Often many males find the same female and wrap around her to copulate with her. Such a "breeding ball" of up to 12 males can stay in this position for two to four weeks as males wrestle in slow-motion to mate with the female.
During mating, males use their spurs to arouse the female. They aggressively press their regions hard against the female body, while continuously scratching her with their spurs. This can produce a scratching sound. Mating approaches its climax when the stimulus of the males' spurs induces the female to raise her cloacal region, allowing the cloacae of the two snakes to move together. The male then coils his tail around the female, and they copulate. Often, the strongest and largest male wins, but the females may choose another male as they are much larger and stronger. Courtship and mating occur almost exclusively in water.
Mating is followed by a gestation period of six to seven months. The species is Oviparity, with females giving birth to live young. Litters usually consist of 20 to 40 offspring, although as many as 100 may be produced. After giving birth, females may lose up to half their weight.
Neonates are around long and receive no parental care. Because of their small size, they often fall prey to other animals. If they survive, they grow quickly until sexual maturity in a few years, then grow more slowly.
When no males are available, facultative parthenogenesis is possible, producing viable homozygous litter. In 2014, a green anaconda in West Midland Safari Park gave birth to three young through parthenogenesis.
/ref> Some feed on carrion and conspecifics, usually inside or around water. Large anacondas can go weeks to months without food after a large meal, because they have a low metabolism. Females have increased postpartum feeding to recover from their reproductive investment.
Predators
Although the green anaconda is an apex predator, even large adult specimens are part of the diet of , , American crocodiles and Orinoco crocodiles.
Reproduction
Individuals are solitary until the mating season, which occurs during the rainy season, and can last several months, usually from April to May. Typically, females leave pheromone trails for males to follow, but how males track it is unclear. It may be that the pheromone is airborne. This theory is supported by the observation of females that remain motionless, while many males move towards them from all directions. Male anacondas also often flick their tongues to sense chemicals that signal the presence of a female. (2025). 9780761472667, Cavendish Square. ISBN 9780761472667 .
Longevity
Green anacondas in the wild live for about 10 years. In captivity, they can live 30 years or more. The 2023 Guinness Book of World Records for the oldest living snake in captivity is a green anaconda aged 37 years 317 days, verified on 14 May 2021 by Paul Swires, at Montecasino Bird & Reptile Park in Johannesburg, South Africa.
In popular culture
Anacondas have been portrayed in horror literature and films, often incredibly gigantic, agile and with the ability to swallow adult humans. These traits are occasionally attributed to other species, such as the Burmese python and the reticulated python, but to less extent than to the green anaconda. Despite having the capability to overpower a man, there is no verified evidence of this species consuming humans, unlike the reticulated python. This is possibly because large specimens inhabit remote areas deep inside the Amazon jungle, which is isolated from humans, unlike the python in Asia. Among the most popular of such films are the 1997 film Anaconda and its four sequels.
Bibliography
Further reading
(2025). 9783931587437, Natur und Tier-Verlag. ISBN 9783931587437
External links
Categories: Apex Predators, Eunectes, Fauna Of The Amazon, Reptiles Described In 1758, Reptiles Of The Caribbean, Reptiles Of Bolivia, Snakes Of Brazil, Reptiles Of Colombia, Reptiles Of Ecuador, Reptiles Of Guyana, Reptiles Of Paraguay, Reptiles Of Peru, Reptiles Of Trinidad And Tobago, Reptiles Of Venezuela, Animal Taxa Named By Carl Linnaeus
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