Southern limit of the distribution of the green anaconda


* Límite sur de la distribución de la anaconda verde

* Limite sul da distribuição da anaconda verde

In Paraguay, a country located in the center of South America, there are three species of large constrictor snakes: the rainbow boa ("Epicrates cenchria", called salamanta in Brazil), the boa constrictor (scientific name "Boa Constrictor", known in Argentina as boa lampalagua and jibóia in Brazil), and the yellow anaconda ("Eunectes notaeus", also known as southern anaconda). In Guarani, both the boa constrictor and the yellow anaconda are called kuriju.

A reference source on these two types of kurijús is Volume 1 of "Amphibians and reptiles of the Paraguayan Chaco", by American David R. Norman, with photographs by Lawrence Naylor (self-publishing by its author, San Jose, Costa Rica, 1994). These professionals worked for several years in Paraguay, under the auspices of the Peace Corps, working with the National Biological Inventory Project.

Norman reported that the diet of boas includes a variety of mammals, birds and lizards. He tells the story that once, just south of Lieutenant Enciso National Park in the Dry Chaco of Paraguay, a big boa that had finished eating a newborn deer ("Mazama sp.") was found. Norman estimated that that prey size would almost certainly be the most that a boa could swallow. He describes the boa constrictor as a large, heavy snake. There are reports of boas over 4 meters long in other countries, but Norman explains that in the Paraguayan Chaco he never got to see specimens of more than 3 meters long. He concludes that, in the Chaco region, the only snake bigger than the "Boa constrictor" is the southern anaconda or yellow anaconda, scientific name "Eunectes notaeus".

He complements that the "Eunectes notaeus" is an aquatic predator, stalking birds or small mammals by waiting with just part of his head above water. And the story adds that once they saw a yellow anaconda eating a stork, "Mycteria americana", in the Lower Chaco near the Confuso River. About the other kuriju (yellow anaconda), he notes that some biologists have reported yellow anacondas of over 4 meters in length in wetlands around Fort Galpón and Bahia Negra, in the region of the Upper Paraguay River. However, he discloses that most of the specimens in the Lower Chaco near Asunción are 2 to 3 meters long.


In December 2007, a snake of about 7 meters and 90 kilograms was caught by fishermen on the river Aguaray-guasu near Santa Rosa del Aguaray, Paraguay (ABC Color, 4 January 2008), which is located in a latitude of about 24 degrees South. It was a green or northern anaconda, scientific name "Eunectes murinus." In July 2012, another one of 5 m was also found in fishing nets in the river Curuguaty'y, near Colony Jopoi Tava, Yasy Cañy district, department of Canindeyú, Paraguay (Lucy Aquino, personal communication, 3 July 2012; Última Hora, 2 July 2012; Última Hora, 3 July 2012), located further south, in a latitude of about 24 and a half degrees South. This species is famous for being the largest in South America and the second largest in the world after the reticulated python ("Python reticulatis"), a resident of the Old World. But the fact that green anacondas are captured in Paraguay is a rarity.


With the help of Lucy Aquino of WWF-Paraguay, and the very kind attention of Martha Motte of the National Natural History Museum of Paraguay, in San Lorenzo (who contacted me), I got to know a couple of additional documented cases:

1) In February 1981, U.S. scientists Lee Fitzgerald and Norman Scott collected a specimen of "Eunectes murinus" in the Cerro Corá National Park, 3 km from its administration building. The specimen measured 5,1 m long and its skin is now in the Museum, in San Lorenzo.

2) In February 1982, Lucy Aquino collected 0,9 m long baby, also in the Cerro Corá National Park, in Amambay, near the military command headquarters. This small specimen is preserved in a formaldehyde jar in the Museum, in San Lorenzo.

There is good documentation on these two cases, including field notebooks. I got to see both copies, and I communicated personally with all of these researchers. Dr. Fitzgerald reckons that the specimen collected by them was the first known case in Paraguay. Dr. Scott explains that they released the 66-kg green anaconda back where they had found it but just a couple of days later it was sadly killed by an illegal hunter.

3) Besides these, Martha Motte and I found that there is a skin of a third specimen in the cabinets of the Museum. This specimen is even more impressive, with nearly 6 m. Surprisingly there is no documentation about it, but delving into the Museum, Mr. Milciades Valdéz approached us and told us he had brought that specimen from Amambay in the early 80's. At that time, being in the capital city, he was ordered by the then Minister of Agriculture and Livestock to go there and investigate some news that was circulating, that some fishermen had killed "a monster" in the river Aquidabán. It proved to be an "Eunectes murinus" and its recovered skin is the one which was rediscovered in the Museum.


On the other hand, studying in the Zoo and Botanical Garden of Asunción, I could identify more specimens, but there is no documentation regarding them and the officials have a vague or contradictory memory about the events:

a) There is a great skin on display at the Natural History and Indigenist Museum and Herbarium (within the grounds of the Botanical Garden), which according to the taxidermist of the institution is 6,25 m long. It is in a somehow fair condition of preservation, but from what I could see is an "Eunectes murinus." There is not any type of documentation nor could I find any first-hand testimony about its origin (especially if it was found in Paraguay or was brought from abroad) but apparently it has been there for over 20 years.

b) There are three specimens of baby "Eunectes murinus" in this Museum in the Botanical Garden, all embalmed, which according to the taxidermist are offspring of an animal that lived in the Zoo of Asuncion in the late 1970's. The origin and fate of the mother anaconda could not be confirmed, although it is known that the skin in exposition does not belong to it.

c) Dr. Carlos Britos, the Zoo Veterinarian, reports that in 2005 came a juvenile of "Eunectes murinus", of about two meters, from Laguna Blanca, San Pedro, in very poor condition. Unfortunately the skin was not preserved and Dr. Britos could not provide me any documentation.

This last story coincides with a report published by ABC Color, on March 21 of that year, in which the correspondent of that area informs of an anaconda captured in the Laguna Blanca. A picture seems to confirm the species identified by Dr. Britos.


The taxidermist of the Museum insists that the green anaconda is native from Brazil and does not belong to the fauna of Paraguay, although the identification of the individuals exposed are not his specialty. The only document I could find about "Eunectes murinus" in the Zoo of Asuncion is an inventory of more than 10 years ago of living specimens that they had at the time, which included an "Eunectes murinus" but it made it clear that its origin was Brazil .

Martha Motte suggests that the status of the "Eunectes murinus" in Paraguay could be classified as "critically endangered."

Norman Scott recalls that the natural habitat along the Paraná river is now extraordinarily destroyed.

On the subject of the mboi jagua, there is no consensus on whether or not the term should be applied to the green anaconda, as explained in my article "A three-fold interpretation of the snake 'mboi jagua.'" Some experts insist that the mboi jagua is a mythological animal, as reminded by ethnolinguists such as León Cadogan and the editors of the Olga de Maldonado Guarani dictionary.

It is good news that green anacondas continue to be found this far south. What is not good news is that there are people who, through ignorance or greed, are trying to market them. We can not afford to eliminate from those regions such a fabulous species.

Aldo Loup.

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Originally published in ABC Color, on 6 January 2008. Photo: A green anaconda ("Eunectes murinus") in its preferred habitat: water. The easiest way to differentiate it from the yellow anaconda ("Eunectes notaeus") is by the form of its spots. Photo credit: Trisha Shears, 17 February 2007. With permission from Trisha Shears.