Anaconda

Anaconda
Yellow Anaconda, Eunectes notaeus
Scientific classification
Kingdom: Animalia Phylum: Chordata Class: Reptilia Order: Squamata Suborder: Serpentes Family: Boidae Subfamily: Boinae Genus: Eunectes Wagler, 1830
Species
E. beniensis E. deschauenseei E. murinus E. notaeus

Anacondas are four species of aquatic boa inhabiting the swamps and rivers of the dense forests of tropical South America. The Yellow Anaconda can be found as far south as Argentina.

There are two possible origins for the word 'anaconda.' It is perhaps an alteration of the Sinhalese word 'henakanday', meaning 'thunder snake', or alternatively, the Tamil word 'anaikondran', which means 'elephant killer'. It is unclear how the name originated so far from the snake's native habitat; it is likely due to its vague similarity to the large Asian pythons. Local names for the anaconda in South America include the Spanish term matatoro, meaning 'bull killer', and the Native American terms sucuri, yakumama, and jibóia. Anacondas as members of the boa family are sometimes called water boas. The Latin name for Anaconda is Eunectes.

Overview

Boas are a type of snake that are members of the Boidae family. Boas are basal snakes that are "primitive" in evolutionary terms (i.e. less derived). They are constrictors and most give birth to live young. They have anal spurs, a pair of claws on each side of the cloaca which assist in mating. Boas are named after cows (Latin: bos) because of the old myth that boa snakes pursue cows and suckle them until they are drained to death.

Constriction is a method used by various snake species to kill their prey. Constrictors do not have venom in their fangs to kill prey; instead, they simply squeeze them to death. The snake initially strikes at its prey and holds on, pulling the prey into its coils or, in the case of very large prey, pulling itself onto the prey. The snake will then wrap one or two coils around the prey. Contrary to myth, the snake does not crush the prey, or even break its bones, but instead squeezes, tightening its grip to cut off circulation. The snake can sense the prey's heartbeat and holds firm until the heart, deprived of oxygen, has stopped beating so that the prey will not recover and struggle while being swallowed. The snake then engulfs the prey.

Boa constrictor

Boas have two subfamilies: Boinae or true boas and Erycinae or sand boas. Pythons are sometimes classified as a subfamily of Boidae, but are frequently listed under their own family, Pythonidae. Sand boas are also frequently listed under their own family, Erycidae.

=Boinae subfamiliy

Snakes of the subfamily Boinae are found in Madagascar, Papua, Pacific Islands, and the Neotropics. It has been suggested that genera within each of these particular areas do not form monophyletic groups. True boas are medium to large sized snakes. Females are usually larger than their males. Boas contain many subspecies based on locality. The boas from the Amazon Basin are the most colorful possessing bright cherry red tails. It used to be said that boas were New World Snakes and pythons were Old World Snakes, but, with boas found on Madagascar, Fiji, and Solomon Islands, this is not quite true. Instead, it is possible that boas have survived in evolutionarily isolated areas. South America, until a few million years ago, had a distinct fauna that included marsupial mammals; with the land bridge to North America, boas have migrated north as placental mammals and colubrids have migrated south.

• Boa (one species: Boa constrictor, also called the Red-tailed Boa, )
• Acrantophis (Dumeril's Boa and Madagascar Ground Boa; sometimes equated with Boa)
• Sanzinia (Madagascar Tree Boa; sometimes equated with Boa)
• Eunectes (Anacondas)
• Corallus (Tree boas)
• Epicrates (Rainbow boas)
• Candoia (Pacific boas)

File:Argentine Boa.JPG

An Argentine Boa

File:0080caroni3.JPG

Cook's Tree Boa

Erycinae subfamiliy

Compared to true boas, erycines are quite small, with most members remaining well under a meter in length. Fossil erycines have been found in rock strata over 50 million years old, and were once widespread in North America. Now, only two species remain in North America, as well as the sand boas in Africa, Asia and southeastern Europe.

At least three erycine species lay eggs: the Calabar Boa, (Calabaria reinhardtii) (once classified as a python for this reason); the Arabian Sand Boa, (Eryx jayakari); and the West African Sand Boa, (Eryx muelleri).

• Eryx (Sand boas)
• Gongylophis (Rough-tailed Sand Boa)
• Charina (Rubber Boas)
• Lichanura (Rosy boa, sometimes equated with Charina)
• Calabarinae (Calabar Python, sometimes equated with Charina

Species

• Bolivian Anaconda, Eunectes beniensis
• Dark-spotted Anaconda, Eunectes deschauenseei
• Green Anaconda, Eunectes murinus
• Yellow Anaconda, Eunectes notaeus

Green anaconda

The Green Anaconda (Eunectes murinus) is an anaconda. It is the largest member of the boa family of snakes and the most heavy bodied member of the super-order Squamata.

It is among the largest snakes in the world, with recorded (but unverified) measurements of 9.45 m (29.7 feet) and 11 m (33.5 feet), though average size is closer to 31 feet.^{[citation needed]} It rivals the Reticulated Python for length, but is typically considerably heavier. It can weigh 250 kg (551 lb) and have a girth of more than 30 cm (11.8 inches) in diameter.^{[citation needed]} The Green Anaconda might be the most exaggerated animal on earth in terms of size, with reports of lengths ranging up to 40 m (131 feet). Probably the largest snake ever actually measured was a shot-but-not-killed female near the Colombia-Venezuela border in 1944. This unweighed giant was measured as being 11.43 m (37.5 feet), before it apparently slithered off from its hunter, who thought it died. Females are significantly larger than males, having the largest sexual dimorphism of all the snakes.

Their primary overall color is an olive green, with black blotches that run the length of the body. Their head is narrow compared to the rest of the body, with most exhibiting distinctive orange-yellow striping on either side. Their eyes are set high on their head so as to allow the snake to be able to see out of the water without exposing the rest of its body.

Green Anacondas are found mainly in northern South America (Amazon and Orinoco basins), in Venezuela, Colombia, Brazil, northern Bolivia, northeast Peru, Guyana, and the island of Trinidad.

Green anaconda at the New England Aquarium.

Green anacondas, like all anacondas, are primarily aquatic. They eat a wide variety of prey, almost anything they can manage to overpower, including: fish, birds, a variety of mammals, and other reptiles. Particularly large anacondas may even consume large prey such as tapir, deer, capybara, caiman, and sometimes crocodiles and jaguars, but such large meals are not regularly consumed. A human would be too big for even an anaconda to swallow. They employ constriction to subdue their prey. Cannibalism among green anacondas is also known, most recorded cases involving a larger female consuming a smaller male. Scientists cite several possible reasons for this, including the dramatic sexual dimorphism in the species and the possibility that female anacondas require additional food intake after breeding to sustain their long gestation period and the male simply being an opportunistic prey item, but the exact reason is not understood. In captivity, anacondas are known for their aggressive disposition.

Anacondas are ovoviviparous. Copulation takes place during the rainy season, typically in the water. Gestation is approximately 6 months. Litter size averages 20-40 young, but as many as 100 are possible. Sexual maturity is reached between 2 and 3 years of age.

Yellow anaconda

The Yellow Anaconda (Eunectes notaeus), is a species of anaconda. They are native in South America in countries such as Bolivia, Paraguay, Uruguay, western Brazil, and northeast Argentina. It is smaller than the more well known green anaconda and reaches an average adult length of about 3 metres (9.8 feet). They have a yellowy brown base colour with black blotches and rossettes. They live in mostly aquatic habitats including swamps, marshes, and brush covered banks of slow moving rivers and streams. Their diet includes deer, wild Pigs, Birds and large rodents and also aquatic animals such as fish.

Giant Anacondas

There is some debate about the maximum size of anacondas, and there have been unverified claims of enormous snakes alleged to be as long as 30-45m (100-150ft).

According to Lee Krystek , a 1944 petroleum expedition in Colombia claimed to have measured an 11.4m (37.5ft) specimen, but this claim is not always regarded as reliable; perhaps a more credible report came from scientist Vincent Roth, who claimed to have shot and killed a 10.3m (34ft) anaconda in Guyana.

There are some reports from early European explorers of the South American jungles seeing giant anacondas up to 18.2m (60ft) long, and some of the native peoples have reported seeing anacondas up to 15.2m (50ft) long., but these reports remain unverified.

Another claim of an extraordinary size anaconda was made by adventurer Percy Fawcett. During his 1906 expedition, Fawcett wrote that he had shot an anaconda that measured some 18.9m (62 ft) from nose to tail. Once published, Fawcett’s account was widely ridiculed. Decades later, Belgian zoologist Bernard Heuvelmans came to Fawcett's defence, arguing that Fawcett's writing was generally honest and reliable.

Historian Mike Dash writes of claims of still larger anacondas, alleged to be as long as 30-45m (100-150ft) — some of the sightings supported with photos (although those photos lack scale). Dash notes that if a 50-60 ft anaconda strains credulity, then a 150ft long specimen is generally regarded as an outright impossibility.

It should be noted that the Wildlife Conservation Society has, since the early 20th century, offered a large cash reward (now grown to $50,000 USD) for live delivery of any snake of 30 feet or more in length. The prize has never been claimed. Also, in a study of 1000 wild anacondas in Brazil, the largest captured was 17 feet long.

References

ISBN links support NWE through referral fees

• Bernard Heuvelmans (1958). On the Track of Unknown Animals. Hill and Wang. ISBN 0710304986. 

External links

• Anacondas.org - Jesus Rivas Home Page
• Animal Diversity Web: Eunectes murinus (green anaconda)

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