The green anaconda (Eunectes murinus), common anaconda, common water boa, akayima, or sucuri, is a boa species found in South America. It is one of the longest and heaviest known extant snake species. Like all boas, it is a non-venomous constrictor. Green anacondas only have a lifespan of 10 years in the wild, although some specimens live longer when they are taken care of in captivity. Green anacondas live in tropical rainforests and tend to prefer shallow, slow-moving waters, such as streams, rivers and flooded grasslands. They spend most of their time in the water but are also found on land in thick vegetation.

Taxonomy

thumb|A anaconda skeleton on display at [[Museum of Osteology with other squamates ]]

In the famous 10th edition of Systema Naturae of 1758, Carl Linnaeus cited descriptions by Albertus Seba and by Laurens Theodorus Gronovius to erect the distinct species murina of his new genus Boa, which contained eight other species, including Boa constrictor. The generic name Boa came from an ancient Latin word for a type of large snake. The first specimens of Boa murina were of immature individuals from in length. In 1830, Johann Georg Wagler erected the separate genus Eunectes for Linnaeus's Boa murina after more and larger specimens were known and described. Because of the masculine gender of Eunectes, the feminine Latin specific name murina was changed to murinus.

Linnaeus almost certainly chose the scientific name Boa murina based on the original Latin description given by Albertus Seba in 1735: [tortoise-patterned (spotted) American snake, a predator that lies in wait for mice (and rats)]. The Latin adjective (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 , as now often wrongly indicated for E. murinus. The word akayima and variants (okoyimo, okoimo) have been used by the local Carib 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).

Description

thumb|An anaconda at the [[New England Aquarium]]

The green anaconda is the world's heaviest and one of the world's longest snakes, reaching a length of up to long. More typical mature specimens reportedly can range up to , with adult females, with a mean length of about , being generally much larger than the males, which average around . Weights are less well studied, though reportedly range from in a typical adult.

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. The longest and heaviest verified specimen encountered by 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 .

Difficulties in determining the maximum size of anacondas

The remote location of the snake's habitat has historically made locating, capturing, and returning specimens difficult. Transporting very large specimens to museums, especially before substantial decay, is difficult, though this has not prevented the return of much larger and more cumbersome crocodilian specimens.

Historical records

Numerous historical accounts of green anacondas are reported, often of improbable sizes. Several zoologists, notably Henry Walter Bates and Alfred Russel Wallace, among others, note rumors of snakes beyond long, but in each case, their direct observations were limited to snakes around in length. Numerous estimates and second-hand accounts abound, but are generally considered unreliable. To prove the point of overestimating, in Guyana in 1937, zoologist Alpheus Hyatt Verrill asked the expedition team he was with to estimate the length of a large, curled-up anaconda on a rock. The team's guesses ran from . When measured, this specimen was found to be .

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 .

Estimates of maximal size

Size presents challenges to attain breeding conditions in larger female anacondas. While larger sizes provide the benefit of a larger number of offspring per clutch, the breeding frequency of the individuals reduces with size, indicating that a point exists at which the advantage of a larger clutch size is negated by the female no longer being able to breed.

The minimum size of breeding anacondas in a survey of 780 individuals was in snout–vent length, indicating that the maximum size attained by anacondas following this pattern would be in snout–vent length. The type locality given is "America". 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 and potentially prey on native wildlife, such as white-tailed deer, American alligators, American crocodiles, wading birds, other birds, mammals and reptiles. 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. They float underwater and are known to swim quickly. Their eyes and nose are located on the top of the head, allowing the snake to breathe and watch for prey while the rest of the body is hidden underwater. When prey passes by or stops to drink, the anaconda strikes, without eating or swallowing it, and coils around it with its body, then constricts and suffocates the prey to death. Particularly large anacondas may consume tapirs, deer, peccaries, capybaras, jaguars, and caimans, but such large meals are rare. 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.

In southeastern Peru, potential prey of green anacondas include collared peccaries, lowland pacas, brocket deer (Mazama sp.), brown agoutis, cocoi herons, neotropical otters, gold tegus, spectacled caiman, and giant otters. 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 domestic dogs, chickens, cattle, water buffalo, sheep, domestic cats, and wild boar.

Predators

Although the green anaconda is an apex predator, even large adult specimens are part of the diet of Orinoco crocodiles, black caimans and jaguars.

Reproduction

thumb|240px|A skeleton of E. murinus, exhibited at the [[National Museum of Nature and Science, Tokyo, Japan]]

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.

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 cloacal 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 ovoviviparous, 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.

<!-- not encyclopedic - how-to ==Captivity==

One may reasonably maintain an average and acceptable temperature for the snake by the use of a heating element or infrared light bulbs. A gradient must be offered within the enclosure to allow the snake to bask in the heat or go to cooler areas in the tank. Optimum humidity can be difficult to maintain and research must be done on the snake to determine the correct level. More than 80% humidity must be maintained for caging an anaconda species from the tropical region, while a slightly less than 30% humidity must be maintained for a species of a desert region.

Photoperiods are often used with most species of snake; natural light is best for this, but low UV percentage bulbs can also be used. Captive anacondas have a reputation for unpredictability and aggression due to the temperaments of wild-caught specimens first collected for captive breeding, but with proper care, green anacondas can and do make for calm, relatively sedate pets. Due to their immense size and power, however, proper respect and caution should always be maintained, and they are best left to experienced adult owners who can provide them with the proper requirements.

It is not recommended to get one of these snakes unless you have experience with other large snakes. Large snakes require large setups and extensive care. You also need to be willing to feed these snakes large prey items such as rabbits. Anaconda's like to spend a large amount of time in water. It is very difficult to offer a Green Anaconda a setup that has enough water for them to swim in due to the volume of water that would be required. -->

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.

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.

References

Bibliography

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Further reading