The Green Anaconda (Eunectes murinus)

Nov 24, 2013 Features / Columnists, Interesting Creatures in Guyana

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The green anaconda is the world’s heaviest and one of the world’s longest snakes, reaching more than 6.6 m (22 ft) long. More typical mature specimens reportedly can range up to 5 m (16 ft), with the females, at around a mean length of 4.6 m (15 ft), being generally much larger in adulthood than the male, which averages around 3 m (9.8 ft).  Weights are less well studied, though will reportedly range from 30 to 70 kg (66 to 150 lb) in an average-range adult.

It is the largest snake native to the Americas.
Although it is not as long as the Reticulated python, Eucentes murinus is probably the heaviest extant species of snake or squamate in the world, perhaps only rivalled by the Komodo dragon. Reports of anacondas 35–40 feet or even longer 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 lacking.
The colour 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.
Numerous historical accounts of green anacondas are reported, often of ridiculously improbable sizes.
Size presents challenges to attain breeding condition in larger female anacondas and while larger sizes provide the benefit of larger number of offspring per clutch, the breeding frequency of the individuals reduces with size, indicating that there’s a point in which the advantage of larger clutch size is negated by the female no longer being able to breed, for the anaconda, this limit was estimated at approximately 6.7 m (22 ft) 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 1.5m and 2.5m, the size at maturity.
The minimum size of breeding anacondas in a survey of 780 individuals was 2.1 m (6.9 ft) in snout-vent length, indicating that maximum size attained by anacondas following this pattern would be 5.3 m (17 ft) in snout-vent length.
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 tapirs, deer, capybaras, and caimans, but such large meals are not regularly consumed.
Many local stories and legends report the anaconda as a man-eater, but little evidence supports 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.
While the exact reason for this is not understood, scientists cite several possibilities, including the dramatic sexual dimorphism in the species, and the possibility that a female anaconda requires additional food intake after breeding to sustain the long period of gestation. The nearby male simply provides the opportunistic female a ready source of nutrition.
This species is solitary until the mating season, which occurs during the rainy season, and can last for several months, usually from April to 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.
Many males can 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 two to four weeks. This ball acts as a slow-motion wrestling match between the males, each one fighting for the opportunity 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 induces 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. 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 about six to seven months. The species is ovoviviparous, with females giving birth to live young. Litters usually consists of 20 to 40 offspring, although as many as 100 may be produced. After giving birth, females may lose up to half their weight.
Neonates (babies) 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.
(Source: Wikipedia – The Free Online Encyclopedia)

 

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