Green anaconda (Eunectes murinus)
Description
While
the anaconda may not hold the title of the worlds’ longest snake—coming
second to the reticulated python—its huge girth means that it is
undoubtedly the largest (2).
During the 19th and 20th century, many accounts of giant specimens of
anaconda were reported. While almost certainly exaggerations, it is
possible that in remote, deep rainforest rivers, under optimum
conditions of prey availability, the green anaconda may grow to record
proportions (3). The green anaconda is well-adapted for its semi-aquatic lifestyle, with its eyes and nostrils positioned on top of the ...
Green anaconda fact file
- Description
- Biology
- Range
- Habitat
- Status
- Threats
- Conservation
- Find out more
- Glossary
- References
- Print factsheet
Description
| Kingdom | Animalia |
| Phylum | Chordata |
| Class | Reptilia |
| Order | Squamata |
| Family | Boidae |
| Genus | Eunectes (1) |
- Also known as
- Anaconda, water boa.
Biology
Although
capable of moving over land, the bulky body of the adult green anaconda
is best suited for life in the water, where it gracefully and
stealthily seeks out prey (2) (3) (4).
A variety of prey is taken according to the size of the anaconda, with
smaller individuals taking fish and other small vertebrates, while
larger specimens prey upon deer, capybara, and even full-grown caimans (4) (7). In addition, in rare cases this species has also been known to attack humans (8).
Prey is taken by surprise, with a swift strike from the jaws, after
which coils of the muscular body are quickly thrown around the animal,
often dragging it underwater (4) (7).
Lacking venom, the green anaconda relies on constriction to kill its
prey, asphyxiating the animal, before swallowing it whole. Elastic
ligaments allow the jaws to stretch widely, accommodating prey many
times the width of the head and body. Large meals provide enough
nourishment that the snake can go weeks or months without food (2).
Studies of the green anaconda in seasonally-flooded habitats show that it mates during the dry season, from around mid-February to late May. Males seek out a mate by following scent trails, and due to the greater numbers of males relative to females, several often converge on a single female. This leads to a phenomena known a “breeding ball”, in which the smaller males and the single, large female form a mass of writhing bodies, in which the males attempt push one another out the way in order to access the female’s cloaca and mate (5). This association can last for up to month, during which the female may mate multiple times. This mating system may help to explain the pronounced size difference between the sexes; as larger male specimens can be mistaken for females, it is disadvantageous for males to grow beyond a certain size (9). Interestingly, after mating the female may eat one or more of its mating partners. This behaviour may help it to survive pregnancy, during which food is not taken for up to seven months (10). After mating, in order to survive the dry season, green anacondas shelter underground in mud or caves formed in river banks, or they seek out deeper water (3) (11). The female typically gives birth to litters of 20 to 40 live young, though a record of 82 has been reported. The young measure around 60 centimetres in length, and take roughly six years to reach sexual maturity (2) (3) (4). From birth to adulthood, the green anaconda undergoes a dramatic 500-fold increase in mass, a greater increase than any other snake species (12). While the average lifespan is 10 years in the wild (2), individuals have been known to live for over 25 years (4).
Studies of the green anaconda in seasonally-flooded habitats show that it mates during the dry season, from around mid-February to late May. Males seek out a mate by following scent trails, and due to the greater numbers of males relative to females, several often converge on a single female. This leads to a phenomena known a “breeding ball”, in which the smaller males and the single, large female form a mass of writhing bodies, in which the males attempt push one another out the way in order to access the female’s cloaca and mate (5). This association can last for up to month, during which the female may mate multiple times. This mating system may help to explain the pronounced size difference between the sexes; as larger male specimens can be mistaken for females, it is disadvantageous for males to grow beyond a certain size (9). Interestingly, after mating the female may eat one or more of its mating partners. This behaviour may help it to survive pregnancy, during which food is not taken for up to seven months (10). After mating, in order to survive the dry season, green anacondas shelter underground in mud or caves formed in river banks, or they seek out deeper water (3) (11). The female typically gives birth to litters of 20 to 40 live young, though a record of 82 has been reported. The young measure around 60 centimetres in length, and take roughly six years to reach sexual maturity (2) (3) (4). From birth to adulthood, the green anaconda undergoes a dramatic 500-fold increase in mass, a greater increase than any other snake species (12). While the average lifespan is 10 years in the wild (2), individuals have been known to live for over 25 years (4).
Range
The
green anaconda is found in northern South America, occurring in
Venezuela, Colombia, Brazil, Ecuador, eastern Paraguay, northern
Bolivia, north-east Peru, Guyana and French Guiana. It can also be found
on the island of Trinidad off the north-east coast of Venezuela (4) (6).
More »
Species with a similar range
Habitat
A
semi-aquatic species, the green anaconda is typically found in shallow
water, either in seasonally flooded savanna, such as Llanos grasslands
of Colombia and Venezuela, or in the rivers of the vast Amazon Basin (3). When on land, this species is most commonly found amongst thick vegetation, although it may also climb trees (4) (7).
More »
Species found in a similar habitat
Status
Listed on Appendix II of CITES (1).
Threats
Although
not yet assessed by the IUCN, the green anaconda faces a number of
threats, which could have a significant impact on its population. It is
hunted, both legally and illegally, in many parts of its range for its
skins and for sale in the growing, illegal pet trade. Local people also
frequently kill anacondas under the pretext of protecting livestock,
pets or even people. However, in many cases, a widespread fear and
dislike of snakes results in individuals of this species being
persecuted, even when found in remote areas. Habitat loss and
degradation are also threatening this species, and even in areas where
habitat protection exists, a lack of enforcement is allowing illegal
deforestation to occur (11).
Conservation
The
green anaconda is listed on Appendix II of the Convention on Trade in
International Species (CITES), thereby regulating all commercial trade
in this species through the use of permits and annual export quotas (1).
In addition, in some parts of its range, such as Venezuela, the green
anaconda is protected by national laws, making all use of green anaconda
products illegal. Unfortunately, despite these regulations, illegal
hunting remains problematic. In Bolivia, where hunting is permitted,
efforts have been made to establish a sustainable use program, but at
the current time political unrest has halted its development (11).
Conservation initiatives which can provide a balance between maintaining livelihoods for local people, while maintaining the green anaconda’s population are urgently required to prevent this species’ decline. The development of sustainable use programs is, however, hampered by several factors such as difficulties in obtaining accurate population estimates. Therefore, ecotourism may be one of the most effective ways to conserve this spectacular snake (11).
Conservation initiatives which can provide a balance between maintaining livelihoods for local people, while maintaining the green anaconda’s population are urgently required to prevent this species’ decline. The development of sustainable use programs is, however, hampered by several factors such as difficulties in obtaining accurate population estimates. Therefore, ecotourism may be one of the most effective ways to conserve this spectacular snake (11).
View information on this species at the UNEP World Conservation Monitoring Centre.
Find out more
To learn more about anaconda conservation see:
Rivas, J.A. (2007) Conservation of green anacondas: how Tylenol conservation and macroeconomics threaten the survival of the world's largest snake. Iguana, 14: 74-85. Available at:
http://www.anacondas.org/anacons.htm
To learn more about reptile conservation visit:
International Reptile Conservation Foundation:
http://www.ircf.org
Rivas, J.A. (2007) Conservation of green anacondas: how Tylenol conservation and macroeconomics threaten the survival of the world's largest snake. Iguana, 14: 74-85. Available at:
http://www.anacondas.org/anacons.htm
To learn more about reptile conservation visit:
International Reptile Conservation Foundation:
http://www.ircf.org
Authentication
This
information is awaiting authentication by a species expert, and will be
updated as soon as possible. If you are able to help please contact: arkive@wildscreen.org.uk
Glossary
- Cloaca
- A common cavity into which the reproductive, alimentary and urinary systems open.
References
- CITES (June, 2009)
http://www.cites.org - National Geographic (September, 2009)
http://animals.nationalgeographic.com/animals/reptiles/green-anaconda.html - O'Shea, M. (2007) Boas and Pythons of the World. New Holland Publishers, London.
- Burnie, D. (2001) Animal. Dorling Kindersley, London.
- Rivas, J.A. (2000) Life history of the green anaconda (Eunectes murinus) with emphasis on its reproductive biology. Unpublished Ph. D. dissertation at the University of Tennessee, 0: 1 - 287.
- J. Craig Venter Institute (September, 2009)
http://www.jcvi.org/reptiles/species.php?genus=Eunectes&species=murinus - Boos, H.E.A. (2001) The snakes of Trinidad and Tobago. Texas A and M University Press, College Station, Texas.
- Rivas, J.A. (1999) Predatory attacks of green anacondas (Eunectes murinus) on adult human beings. Herptological Natural History, 6: 158 - 160.
- Rivas, J.A. and Burghardt, G.M. (2001) Sexual size dimorphism in snakes: wearing the snake’s shoes. Animal Behaviour, 62: 1 - 6.
- Rivas, J.A. and Owens, R.Y. (2000) Eunectes murinus (green anaconda): cannibalism. Herpetological Review, 31: 44 - 45.
- Rivas, J.A. (2007) Conservation of green anacondas: how Tylenol conservation and macroeconomics threaten the survival of the world's largest snake. Iguana, 14: 74 - 85.
- Jesus Rivas (September, 2009)
http://www.anacondas.org
Team WILD, an elite squadron of science
superheroes, needs your help! Your mission: protect and conserve the
planet’s species and habitats from destruction.
Please donate to ARKive
No comments:
Post a Comment