Green anaconda
The green anaconda, also known as the giant anaconda, emerald anaconda, common anaconda, common water boa, northern green anaconda, or akayima, is a semi-aquatic boa 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 non-venomous constrictor.
The term "anaconda" often refers to this species, though this term also applies to other members of the genus Eunectes. Fossils of the snake date back to the Late Pleistocene in the Gruta do Urso locality.
Taxonomy
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: "Serpens testudinea americana, murium insidiator" . The Latin adjective murinus 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 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 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. The word akayima and variants 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, such as Eunectes gigas, Eunectes barbouri, and Eunectes akayima. These proposed species are now considered synonymous with E. murinus.
Description
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 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.
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 by flexible ligaments instead of bone. 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.
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. Skins can stretch substantially, increasing the snake's size by more than 50% if stretched during the tanning process.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 that 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.
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.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.
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. For the anaconda, this limit was estimated at in total length. This is consistent with the results of a revision of the size at maturity and maximum size of several snakes from North America, which found that the maximum size is between 1.5 and 2.5 times the size at maturity.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. However, most anacondas are captured from the llanos, 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 it at the top of the food chain.
Distribution and habitat
Eunectes murinus is found in South America east of the Andes, in countries including Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil, the island of Trinidad, and as far south as northern Paraguay. The type locality given is "America".In April 2021, green anacondas were added to Florida's 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, as of 2023 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 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.