Giant Anaconda

The giant anaconda (Sucuriju Gigante or Megaconda) is a cryptid similar to but said to be much larger than the regular anaconda (genus Eunectes).

Early 20th-century European explorers in the Amazon River Basin first learned about supposed giant anacondas from native accounts of fearsome super-sized boas living in the dense jungles.

Some explorers later claimed to have encountered the monsters.

Purported sightings of giant anacondas have been reported in remote areas of the Amazon River Basin, stretching across multiple South American countries, including Brazil, Bolivia, Ecuador, Colombia, Venezuela, Guyana, and Suriname.


Some cryptozoologists believe that giant anacondas — if they exist — are most likely just super-sized anacondas. Others consider them to be an entirely different species unknown to biologists.

Regular anacondas belong to a family of non-venomous constricting snakes commonly known as boas (family Boidae). The family includes boa constrictors and tree boas (genus Corallus) found in the Americas, Asia, Africa, and some parts of the Pacific Islands.

Constricting snakes do not kill prey by injecting venom. They kill by holding on with their fangs, coiling their bodies around, and squeezing until the prey dies of asphyxiation and cardiac arrest.

Boas are similar in size and appearance to pythons, but biologists consider the similarity between the two types of non-venomous constricting snakes to be superficial. Thus, they categorize pythons in the distinct family Pythonidae.

Green Anacondas (Eunectes murinus) are the largest of the four known anaconda species.

Female green anacondas are larger than males and regularly reach 15-20ft in length. But there are claims of specimens reaching and exceeding 30ft and weighing more than 225 kilograms.

The maximum length an anaconda can grow is a subject of longstanding dispute due to the proliferation of scientifically unverified claims. But based on the data from validated measurements, some herpetologists (zoologists who specialize in the study of amphibians and reptiles) believe that 20ft is about the limit.

Although many experts concede that specimens exceeding 20 feet may exist in remote and inaccessible areas of the Amazon jungle, they don’t credit common but unconfirmed claims exceeding 30 feet.

Experts believe that most claims of anaconda lengths greater than 20ft are deliberate exaggeration or unintentional overestimation.

Others note that some of the claims may be due to taking measurements of tanned skins instead of live specimens. Drying or tanning often involves stretching that can increase skin length substantially.

Despite skepticism among biologists, many cryptozoologists believe that giant anacondas exceeding 30ft exist.

In his book Giant Anaconda and Other Cryptids, cryptozoologist Rick Emmer reported that natives of the Amazon River Basin told stories about super-sized aquatic boas in the remote depths of the vast stretch of jungle east of the Andes Mountains.

Detailed descriptions of the alleged monsters are rare, but some sources claim they are similar to regular anacondas in appearance and behavior.

Some cryptozoologists believe the similarities suggest that giant anacondas are only exceptionally large green anacondas and not separate species.

Giant Anacondas, like green anacondas, are supposedly aquatic creatures and adept swimmers. They are said to lurk submerged in shallow, murky, dark, and slow-moving waters, swamps, or marshes with their snouts above the water, waiting for suitable prey to come along.

Regular anacondas feed on small and medium-sized animals, such as rodents, deer, capybaras, opossums, armadillos, monkeys, and birds. They also feed occasionally on domestic animals, such as sheep, goats, and dogs.

However, giant anacondas are alleged to prey on larger animals, including panthers, crocodiles, cattle, and even full-grown humans.

Giant anacondas would presumably kill their prey using the same method as green anacondas — grasping prey in their powerful jaws, and holding on with their fangs before coiling around and squeezing it to death.

Descriptions of giant anacondas make them similar in physical appearance to the green anaconda. The similarities further suggest that giant anacondas are probably only larger-than-normal anacondas.

The alleged physical traits include green skin with large black blotches and a yellowish underside.

Another reported trait that suggests giant anacondas are only oversized green anacondas is the claim that they give off an awful stench.

The British explorer Percy Fawcett, one of the first Europeans to report an encounter with a supposed giant anaconda, said the monster gave off a terrible “fetid odor.”

Although the explorer thought that the stench from the alleged 62-foot monster was due to its breath, we know that green anacondas release a foul-smelling substance from their cloacal region when distressed.

Father Victor Heinz, who reported (October 1929) an encounter with a massive aquatic serpent he believed to be a giant anaconda, said the fearsome beast had eyes that glowed blue-green in the dark.

Native folklore identifies giant anacondas with supernatural shapeshifting creatures or Boiuna that can take on human form. Other myths and legends identify giant anacondas with the mythical M’boi or Yacumama.

Yacumama is a gigantic serpentine water goddess said to live in the Peruvian Amazon Rainforest.

Although living giant anacondas have not been scientifically verified, fossil records reveal that a gigantic boa named Titanoboa (Titanoboa cerrejonensis) existed more than 56-66 million years ago in the Paleocene epoch after the extinction of the dinosaurs.

Researchers first found Titanoboa fossils in 2009 in the Cerrejón coal mine west of Lake Maracaibo in the La Guajira region of northeastern Colombia. They estimated that fully-grown individuals reached about 45 feet in length and may have weighed 2.5 tons.

The extinct species is related to extant anacondas and other members of the boa species. The fact that Titanoboa belonged to the same family as modern anacondas led some cryptozoologists to suggest that giant anacondas may be surviving Titanoboas.

Sightings and Tales

Percy H. Fawcett

The British military officer and explorer Percy H. Fawcett reported the first widely known sighting of a supposed giant anaconda.

Fawcett arrived in the Amazon River Basin region in 1906 as an agent of the Royal Geographical Society. He was tasked with mapping the border between Brazil and Bolivia. While traveling, he met a local who claimed to have killed a gigantic boa nearly 60 feet long.

According to the cryptozoologist Rick Emmer, Fawcett thought the person was exaggerating and thus dismissed the story.

However, months later, while attempting to reach a remote location of the Amazon River Basin in a dugout canoe, Fawcett and his team are said to have encountered a giant anaconda.

The monstrous creature is said to have swum past their canoe and slithered up the riverbank. Apparently believing it was the giant anaconda that natives had described, the explorer grabbed his rifle and killed the beast. The team examined the animal and estimated its length at about 62 feet (19m).

Fawcett noted in his account that locals reported seeing huge tracks in the swamps that suggested the presence of a small population of apparent giant anacondas in the jungle. He claimed that a Brazilian Boundary Commission once told him about a specimen that was 80ft in length.

Herpetologists and naturalists did not take Fawcett’s claims seriously.

However, in the decades following his report, multiple explorers came forward with other accounts of giant anaconda sightings.

Vincent Roth

The Australian scientist and explorer Vincent Roth explored Guyana’s hinterland (1889-1935) and published a two-volume account of his experience in his book, A Life in Guyana (Volumes I & II).

Roth claimed to have shot a giant anaconda measuring 34ft (10.3 meters).

George Gardner

In his 1846 book Travels in the Interior of Brazil, 1836–41, the Scottish botanist George Gardner reported a 33-foot specimen.

A petroleum prospecting expedition in Columbia (1944) claimed to have shot an anaconda measuring 37.5ft.

Lorenz Hagenback

The explorer and animal collector Lorenz Hagenback reported that two Roman Catholic priests, Father Victor Heinz and Father Protesius Frickel, claimed to have encountered an 80-foot monster while traveling by canoe on the Amazon in 1922.

Newspaper reports

According to cryptozoologist Rory Storm in his book Monster Hunt: The Guide to Cryptozoology (2008), Brazilian newspapers published alleged photos of super-sized anacondas caught in the Amazon River. One published by Diario in 1948 showed a giant anaconda allegedly measuring 131 feet and weighing 5 tons.

Another published by A Noite Illustrada allegedly showed a monster measuring 115 feet.

However, experts considered the photographs unreliable because there were no references to help estimate the actual size of the snakes.

Mike Warner reported in 2011 that an Irish cryptid hunter Mike Warner, “recently” returned from a two-week expedition to the Amazon River Basin with a photo allegedly showing a 120-foot monster.

Juan Carlos Palomino

Slate also reported that Peruvian army veteran Juan Carlos Palomino claimed his commando unit once shot a 40-foot giant anaconda, but senior officers took the carcass.

Col. Remy Van Lierde

Belgian Air Force officer Col. Remy Van Lierde (see video below) claimed a rare sighting in Africa. While flying with two passengers over a remote area of the Katanga province in Belgian Congo in 1959, he sighted what looked like a giant snake in the bush below.

He made multiple passes over the spot for a better look at the alleged monster and snapped a photo. The colonel estimated the length of the snake at 50 feet.

However, biologists believe that the African rock python (Python sebae) is the largest African snake and that they only grow to about 20ft(6 m).

Other Name/sSucuriju gigante, Megaconda, Boitata, M’boi, Yacumama, Matatoro (“bull killer”), Boiuna
LocationBolivia, Brazil, Colombia, Ecuador, Guyana, Peru, Suriname, Venezuela, 
HabitatJungle, Marsh, River, Swamp


Giant Anaconda and Other Cryptids: Fact Or Fiction? Rick Emmer, 2010

The Monster Book: Creatures, Beasts and Fiends of Nature, Nicholas Redfern, 2016

Monster Hunt: The Guide to Cryptozoology, Rory Storm, 2008

Vincent Roth, A Life in Guyana, Volume 1: A Young Man’s Journey, 1889–1923

Vincent Roth, A Life in Guyana, Volume 2: The Later Years, 1923–1935

Travels in the Interior of Brazil: Principally Through the Northern Provinces, and the Gold and Diamond Districts, During the Years 1836-1841 (published 1846), “On the Trail of a 40-Foot Anaconda: The fifth hidden wonder of South America,” accessed January 20, 2023.

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