Eunectes murinus
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| Green Anaconda | |
|---|---|
 | |
| Conservation status | |
| Not evaluated (IUCN 3.1) | |
| Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Boidae |
| Subfamily: | Boinae |
| Genus: | Eunectes |
| Species: | E. murinus |
| Binomial name | |
| Eunectes murinus (Linnaeus, 1758) | |
| Synonyms | |
| |
Eunectes murinus (derived from the Greek "Ευνήκτης" meaning "good swimmer" and the Latin "murinus" translated into "he who predates on mice") is a non-venomous boa species found in South America. It is the most massive of all known snake species. Two subspecies are currently recognized, including the nominate subspecies described here.[4] The term "anaconda" (without any further description) often refers to this species, though the term could also apply to several other members of the genus.
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Profile
The Green Anaconda is one of the world's longest snakes, reaching 5–7 m (18-23ft) long (known to be exceeded only by the reticulated python Python reticulatus). Reports of anacondas 35-40 feet also exist but such claims need to be regarded with caution as no specimens of such lengths have ever been deposited in a museum and hard evidence is required.[5] There is a $50,000 cash reward for anyone that can catch an anaconda 30 feet or longer, but the prize has not been claimed yet.[6] Although the reticulated python is longer, the anaconda is the heaviest snake. The longest (and heaviest) scientifically recorded specimen was a female measuring 521 cm (17.1 ft) in length and weighing 97.5 kg (214 lbs). [7]
The color pattern consists of 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.
Common names
Anaconda, common anaconda, water boa,[2] green anaconda.[3]
Local names in South America include the Spanish term "matatoro," meaning "bull killer," and the Native American terms sucuri and "yakumama" in the Peruvian region of the Amazon, which means "mother of the water" in the language of the Amazonian Yakurunas or "water people". In Trinidad, it has been traditionally referred to as the huille or huilla (pronounced wheel or wheela).
Geographic range
Found in South America in countries east of the Andes, including Colombia, Venezuela, the Guianas, Ecuador, Peru, Bolivia, Brazil and on the island of Trinidad. The type locality given is "America".[1]
Behaviour
The primarily nocturnal anaconda species tend to spend most of its life in or around water. Anacondas are also sometimes known as the “Water Boa”; they spend more time in water than any of the boas. Because of their large size, they appear rather slow and sluggish when traveling on land. Completely the opposite in water, however, anacondas are known to have the potential to reach high speeds in all depths of water. They tend to float atop the surface of the water with the snout barely poking out above the surface. When prey passes by or stops to drink, a hungry anaconda will snatch it with its jaws (without eating or swallowing it) and coil around it with its body. The snake will then constrict until it has successfully suffocated the prey.[8]
[edit] Feeding
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, jaguars, black caiman, and crocodiles, but such large meals are not regularly consumed. There are many local stories and legends regarding the anaconda as a man-eater, but there is very little evidence to support any such activity. 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 carnivore item, but the exact reason is not understood.[9]
Reproduction
This species is solitary until the mating season, which corresponds to the rainy season, can last for several months, and usually takes place from April–May. During this time, males must find females. Typically, female snakes will lay down a trail of pheromones for the males to follow, but it is still unclear how the males of this species track a female's scent. Another possibility is that the female releases an airborne stimulant. This theory is supported by the observation of females that remain motionless while many males move towards them from all directions. Male anacondas also frequently flick their tongues to sense chemicals that signal the presence of the female.[citation needed]
In any case, many males often find the same female. Although it may not be necessary for there to be more than one male, this results in odd clusters, referred to as "breeding balls," in which up to 12 males wrap around the same female and attempt to copulate. The group could stay in this position from 2–4 weeks. This ball acts as a slow-motion wrestling match between the males, each one fighting for the right to mate with the female.
During mating, males make use of 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 induce the female snake to raise her cloacal region, allowing the cloacae of the two snakes to move together. The male then coils his tail, surrounding the female and they copulate.[citation needed] The strongest and largest male is often the victor. However, females are physically much larger and stronger and may decide to choose from among the males. Courtship and mating occur almost exclusively in water.
Mating is followed by a gestation period that lasts approximately 6–7 months. The species is ovoviviparous, with females giving birth to live young. Litters usually consists of 20–40 offspring, although as many as 100 may be produced. After giving birth, females may lose up to half their weight.
Neonates are around 70–80 cm long and receive no parental care. Because of their small size, they often fall prey to other animals. Should they survive, they grow rapidly until they reach sexual maturity in their first few years, after which their rate of growth continues at a slower pace.[10]
Captivity
Anacondas, like other snakes and most other reptiles, can quite easily adapt to a change in the climate, environment, and near surroundings when necessary. The reasons for an anaconda's needing to adapt can vary. They may need to adapt to adjust to changes in the availability of food, and any diseases they may be exposed to in new surroundings. An anaconda might also have to adjust to changes in temperature and humidity. Changes in temperature could drastically affect the snake because it is ectothermal, and relies on its environment to control its temperature. If the temperature of its surroundings increases, a snake will do everything possible to prevent its body from over-heating, and if it decreases, it will attempt to lie in heated areas to help maintain its normal temperature. Anacondas, like all other snakes, control and regulate their body temperatures by changing the amount of surface of their skin that is exposed to the sun. If the terrarium, location or "tank" where a reptile is kept, is uniformly heated producing what is known as "the greenhouse effect", then the snake could possibly die from over-heating (hyperthermia). The humidity of its surroundings might also be slightly different than the humidity to which the snake was previously accustomed. This could, potentially, drastically alter its shedding cycle. The obstruction of this cycle is extremely dangerous. The hindrance of an anaconda's shedding cycle most often causes retention of eye caps.[11] Due to these conditions and emotions of the snake, anacondas are known for their aggressive disposition when being held in captivity.[12]
Environmental requirements
One may reasonably maintain an average and acceptable temperature for the snake by the use of a simple heater and infrared light bulbs. Anacondas and other snakes must be exposed to ultraviolet (UV) radiation. This is exceptionally significant because the snake needs it to produce vitamin D3 for further bone development in its body. Occasional exposure to light bulbs that emit UV radiation with proper wavelength, or better yet, the sun, is also necessary to maintain the positive health of an anaconda. Optimum humidity can be difficult to maintain and research must be done on the snake to determine the correct level. A percentage of just less 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.[13]
Subspecies
| Subspecies[4] | Taxon author[4] | Common name | Geographic range |
|---|---|---|---|
| E. m. gigas | (Latreille, 1801) | ||
| E. m. murinus | (Linnaeus, 1758) |
Entertainment
These snakes are among the most dramatized and most terrifying of villains portrayed in natural horror films, supposedly growing to over 120 feet in length and able to swallow adult humans; traits that are occasionally also attributed to other species, such as the Burmese python and the boa constrictor. Among the most popular snake films that feature it are the 1997 film, Anaconda, along with its three sequels Anacondas: The Hunt for the Blood Orchid, Anaconda 3: Offspring and Anacondas: Trail of Blood. This species is also the main antagonist in Mathias Bradley's novel, Anacondas: The Terror of the Amazon Rainforest, in which multiple hybrid anacondas escape from a research facility in the Amazon Rainforest and come into contact with a toxic chemical that causes them to rapidly mutate into gigantic snakes. A more positive depiction of the anaconda exists in the short stories "Anaconda" and "El Regreso de Anaconda" ("The Return of Anaconda") by Horacio Quiroga, which are told from the anaconda's point of view.
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