The generic name Eunectes derives from Greek and means “good swimmer”; the Neo-Latin specific name notaeus derives from Greek νωταίος/nōtaios (poetic form of Greek νωτιαίος/nōtiaios), here meaning “dorsal”. In distinguishing his new species Eunectes notaeus from Eunectes murinus, Edward Drinker Cope stated, “Dorsal scales are larger and in fewer rows."
Adults are not as large as the green anaconda, E. murinus, but nevertheless grow to an average of 3.3 to 4.4 m (11 to 14 ft) in total length. They commonly weigh 25 to 35 kg (55 to 77 lb), though large specimens can weigh 40 to 55 kg (88 to 121 lb) or even more. The maximum size can certainly be larger, although confusion with its larger cousin may complicate matters. Female yellow anacondas have reportedly been measured up to 4.6 m (15 ft). Females are larger than males.
The color pattern consists of a yellow, golden-tan or greenish-yellow ground color overlaid with a series of black or dark brown saddles, blotches, spots and streaks.
This species prefers mostly aquatic habitats, including swamps, marshes, and brush-covered banks of slow-moving rivers and streams. They can be also observed in forests searching for large game, such as brocket deer, or peccaries.
These snakes were studied in regularly flooded areas in the Pantanal region of southwestern Brazil. The data collected were directly observed from predatory instances, analysis and examination of gut and waste contents, and affirmations by local residents and other researchers. These studies indicate the species is a generalist feeder. The prey list analyzed and other evidence suggest E. notaeus employs both "ambush predation" and "wide-foraging" strategies. The snakes forage predominately in open, flooded habitats, in relatively shallow water; most predation instances occur from June to November, when flooded areas have noticeably dried out, with wading birds being the most common prey. They have also been known to prey on fish, turtles, small-sized caimans, lizards, birds' eggs, small mammals and fish carrion. The prey to predator weight ratio is often much higher than those known for other types of Boidae.
For the most part, yellow anacondas are sequentially monogamous. Males become attracted to females when she produces pheromones released into the air. Males then follow the scent to the female and courtship begins. This courtship will normally take place in water and may last for quite some time. They have been known to form breeding balls consisting of one female and several males. These breeding balls have been known to stay together for up to a month. In the breeding ball, males compete for mating access to the female. Normally the largest male will win successfully out compete other males. Larger males may successfully breed with more females as a result. Mating system is polygynous, or polygynandrous (promiscuous ).
They breed only once yearly. Breeding usually occurs from April to May. About 4-82 offspring are lay at once. Females, after 6 months gestation period, give birth to fully developed live young. These young are immediately able to live on their own. They have indeterminate growth. Female reach sexual maturity from 3–4 years after birth. Males from 3–4 years also. Females provide significant resources to their young during incubation, but young are independent at birth and there is no further parental care.
Typical lifespan of yellow anacondas in the wild is 15–20 years. In captivity, it becomes much longer, about 23 years maximum.
Communication and perception
Yellow anacondas are solitary animals, except in breeding season. When courtship, they communicate by rubbing one another and proceed with courtship. As anacondas have heat sensing pits located along their mouths, pits used to find prey by detecting heat of the prey. They pick vibrations through their jaws.
As captives, they have a reputation for being unpredictable.
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- Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. ISBN 0-8069-6460-X.
- "Eunectes notaeus". Integrated Taxonomic Information System. Retrieved 3 July 2008.
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- What Is a Yellow Anaconda? Wisegeek.com. Retrieved on 2012-08-22.
- Mendez M, Waller T, Micucci P, Alvarenga E, and Morales JC (2007). Genetic population structure of the yellow anaconda (Eunectes notaeus) in Northern Argentina: management implications. In: Biology of the Boas and Pythons, Robert W. Henderson and Robert Powell (eds) pp. 405–415. Eagle Mountain Publishing, LC ISBN 0972015434.
- Owen, W. 2004. Snakes: Reptiles. p. 397 in J Flew, L Humphries (eds.) The Encyclopedia of Animals, Vol. 1. Los Angeles: University of California Press.
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