One of the largest snakes in the world, the green anaconda can reach impressive proportions — over 30 feet ( m) in length, 12 inches ( Learn more about the Green anaconda – with amazing Green anaconda videos, photos and facts on Arkive. Common Name: Green Anaconda. Scientific Name: Eunectes murinus. Type: Reptiles. Diet: Carnivores. Group Name: Bed, knot. Average life span in The Wild: .

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Green anacondas are found throughout the tropical lowlands of South America. This species is particularly common in the Orinoco basin of eastern Columbia, Amazon River basin of Brazil, and the seasonally flooded Llanos grasslands of Venezuela. Small populations of green anacondas have also been introduced into Florida. Green anacondas are semi-aquatic snakes that inhabit shallow, slow-moving freshwater habitats, as well as tropical savannas, grasslands, and rainforests. Green anacondas are one of four closely related species of constrictors, the other species being Eunectes notaeus yellow anacondaE.

These boas can be distinguished from other constricting snakes by the absence of the supraorbital bone in the roof of the skull. Boas have an external horny claw, a hind limb remnant that is more evident in males than in females.

Green anaconda coloration is characteristically dark olive-green dorsally, gradually changing to yellow ventrally. They have round dorsal blotches that are brown with diffused black borders, and are dispersed over the mid to posterior length of their body. Like other Eunectes species, they have narrow ventral scales and small, smooth dorsal scales.

The scale plates at the anterior portion of their body are much larger than those at the posterior end. Their skin is soft, loose, and can endure extended periods of water absorption.

Anacondas have dorsal nostrils and small eyes that are positioned on the top of the head. They also have a prominent black post-ocular stripe that runs from the eye to the angle of the jaw.

Green anaconda

Hsiou and Albino, ; O’Shea, Green anacondas are the largest snakes in the world. There are records of 10 to 12 meter anacondas weighing up to kg, though the actual maximal size of an anaconda is the subject of much dispute. Females typically have a much larger mass and length than males, with males reaching an average of 3 meters in length and females 6 meters.

The sex of an anaconda is also reflected by the size of the spurs located in the cloacal region. Males have larger spurs 7. Duellman, ; Grzimek, ; Miller, et al. Green anaconda neonates are larger than most snakes at birth. They then undergo a murnus increase in biomass from birth to adulthood. Anacondas start to show evidence of sexual dimorphism after the first year of life.

Grzimek, ; Lamonica, et al. There are differences in rates of development between savanna and river-dwelling snakes. Strong murnus of prey availability may be present in savanna environments, with the result that river-dwelling individuals often are larger and heavier than savanna-dwelling snakes. Grzimek, ; O’Shea, ; Rivas, Green anacondas are polyandrous. Studies have reported that green anacondas breed in multiple-male aggregations of up to 13 males. Mating can last for several weeks.


During this time, a female can mate several times with the courting males. Males surround the female to make a breeding ball, in which the snakes form a mass of writhing bodies.

Males compete to gain access to the female by coiling around her, searching for her cloaca with their tails. Visual or chemical cues do not seem to be involved. Females are selective in mating aggregations. In conditions of high density or when females are easy to track, males can encounter each other, which may lead to combat. However, male-to-male combat is rare. If one male is exceptionally large, it can be mistaken for a female by other males and may be courted.

Large males typically mate with the most fertile and largest females. Rivas and Burghardt, ; Rivas, Green anacondas reach sexual maturity at approximately 3—4 years of age. Mating occurs during the dry season, between March and May, with males searching for females to mate with. Males have short term sperm storage, using up their reservoir after mating is completed.

After mating, the female may eat one or more of her mating partners, as she does not take in food for up to seven months. This behavior may be beneficial in helping her to survive through the gestation period.

Afterwards, males usually leave the impregnated female and return to their home ranges; the female does not migrate. Duellman, ; Miller, et al. Females are ovoviviparous and incubate their eggs for 7 months until they give birth to live young.

Their movements and foraging behaviors are limited to avoid compromising the health and success of their clutch. Females give birth in shallow water during the evening or late afternoon, at the end of the wet season.

Females may give birth to as many as 82 young, averaging offspring. Scientists report an association between clutch size and the size of the female, with large females typically having larger clutch sizes than smaller females. This association may be due to greater fat reserves in larger individuals. On average, these snakes breed every other year, allowing recuperation from the loss of energy required for reproduction.

Maternal provisioning and protection occurs throughout the gestation period. After birth, offspring are independent and receive no parental care. Duellman, ; Grzimek, The lifespan of green anacondas in the wild averages 10 years. In captivity, they may live for over 30 years. Anacondas are readily adaptable to changes in their environment. Such adaptability is useful during the annual dry season of seasonally flooded savannas. In order to survive, the anacondas that live in these areas must either find water or bury themselves in mud.

In the latter case, they will undergo a state of dormancy for the duration of the dry period. Anacondas that reside near river basins are active throughout the year. Alves and Pereira, ; O’Shea, Green anacondas are most active in the early evening. They can move large distances over short time periods, especially during annual dry seasons and when males are seeking females.


They preferentially migrate during cooler hours after the peak heat of the day. Anacondas are poikilotherms, but are able to regulate their body temperatures by changing the amount of surface area that is exposed to the sun.

Grassland-dwelling females remain in areas near river banks, basking in the sun in elevated areas regularly during the wet season. River-dwelling females have been seen to bask on top of dense vegetation.

Non-breeding snakes are rarely seen basking. After the breeding season, they move back to their foraging grounds. Green anacondas have well-defined home ranges. During the dry season, they have small home ranges about 0.

During the wet season, non-breeding females and males migrate to higher elevations and maintain a larger home range estimated to be about 0. They return to their original home range during the dry season.

Eunectes murinus | The Reptile Database

Green anacondas are able to detect approaching animals using vibrations. They are also able to detect chemical cues of eundctes animals in the air using eunectez forked tongues and Jacobson’s organs. Male anacondas also use these structures to detect the pheromones of nearby females during the mating season. In addition to their chemosensory abilities, anacondas have pit organs along the upper lip, which are able to sense heat signatures of prey organisms.

They are able to perceive visual and auditory stimuli as well, although these murinux are more poorly developed than the above sensory modalities. O’Shea, ; Pough, et al. Green anacondas are opportunistic apex predators, feeding on any prey that they can kill and swallow. Their diet includes various aquatic and terrestrial vertebrates such as fish, reptiles, amphibians, birds, and mammals. Juvenile anacondas feed on prey such as small birds and juvenile caiman that are typically grams in size.

As they develop, their diet becomes increasingly complex. Prey availability varies more in grasslands than in river basins. Green anacondas take a high risk by feeding on larger prey, which occasionally lead to serious injuries or even death. Some also feed on carrion mueinus conspecifics, usually inside or around water. Occasionally, female green anacondas will feed on males. Large anacondas eunctes go weeks to months without food after eating a large meal, because of their low metabolism.

However, females show increased postpartum feeding rates to recover from their reproductive investment. Green anacondas rely on stealth and ambush techniques as they hunt. Their body pattern provides effective camouflage, allowing a submerged anaconda to be virtually invisible from a short distance away. They attack at any time of day, restraining their prey using their needle-sharp, euneches teeth for a secure grip while killing it by constriction. The more the prey struggles, the tighter the coiling will become, until the victim becomes unconscious.

Death occurs through respiratory arrest and circulatory failure.

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