September 2005
 
 
 
 
 

The Anaconda

Order                       Family                      Genus and Species
Squamata                 Boidae                       Eunectes murinus

The oldest reptile fossil was found in Scotland and dated back more than 340 million years.  Since that
time, reptiles have evolved into many different creatures....from larger reptiles such as crocodiles and
alligators to smaller species represented by over 2600 species of snakes which are found all over the
world.  In this particular study, we will be delving into the Boidae family of snakes which include the
largest snakes on earth....the Anacondas, Boas, and reticulated pythons.  Although the main thrust of
the study will be anacondas, the other related species are also mentioned for reference.

Anacondas are the largest snakes in the world and often reach a length of 25 to 30 feet and weigh over
300 lbs.  There are four different anaconda species which belong to the genus Eunectus 1.barbouri
2.deschauenseei 3.notaeus  and 4. marinus.  The green anaconda, pictured above is the largest of
the Boidae family of giant snakes, followed closely by the reticulated python in size.

All the snakes in the genus Eunectes use their huge size and the ability to constrict their bodies
in a tight coil to squeeze their prey to death.  Immense pressure is exerted on small animals, birds,
and other reptiles....restricting their ability to breathe.  Their lungs and internal organs are ruptured
quickly and the huge snake can then dine at it's leisure.  All snakes have the ability to unhinge their
jaws to be able to swallow prey which is often several times bigger around than they are.  There
have been cases of humans being consumed by the giant snakes of the Boidae family.

The green anaconda is found in South America in the Amazon region and it's tributaries and spends
much of it's time gliding through the jungle swamps and bogs,  which branch off  from the main rivers,
in search of  food.  The anaconda is more at home in and near water than on land, but occasionally
will come up on dry land to sun itself or to hunt for prey.  It contracts it's rib muscles which in turn
sends a rippling motion back towards its tail...propelling the snake silently through the jungle vegetation.
All of the large snakes use this means of locomotion.

The yellow anaconda, pictured above,  is a close relative of the green anaconda although it is a
good deal smaller.  The yellow anaconda also uses its huge body to wrap around its prey and
has a diet which closely resembles the green anaconda...i.e. aquatic animals, small waterfowl,
caymans ( a relative of the crocodile), and a variety of fish.

The large snakes found in the Boidae family do not eat three times a day, in fact, it may be weeks
before they catch and eat any food, but since they are coldblooded and don't require as much food
with as much frequency as a warmblooded creature, they may only require four or five large meals
a year to exist.  Below, an anaconda is constricting the life from a cayman, (a tropical American
crocodilian of the genus Caiman and related genera.  It  resembles and is closely related to alligators.

Anacondas have poor eyesight and hearing but are especially adept at sensing movement, especially
nearby and has a very keen sense of smell and taste.  Unlike most other snakes who can "taste the
air" by flicking their tongue, the anaconda's tongue is not sensitive to outside stimulai except for
touch.  Anacondas have a special chemical receptor, (Jacobson's organ) which is a pair of small blind
pouches or tubes  that are situated one on either side of the nasal septum or in the buccal cavity and
that are reduced to rudimentary pits in adult humans but are more developed in reptiles, amphibians,
and some mammals as chemoreceptors.

Anacondas, as mentioned, can attain a length of up to 35+  feet and weigh over 300 lbs.  They attain
sexual maturity in 3 to 4 years and mate in December and January.  The females gestation period is
around 180-200 days with the number of resulting young depending largely on the size and overall
health of the female but sometimes as many as a 90 to 100 may be born, (although around 20 to 30
babies around two to three feet in length are the normal result).

Unlike most other snake species which lay eggs, the anacondas are viviparous and thus give birth to
live young.   The babies emerge as perfect miniature replicas of their parents and within several days
are ready to go out in search of their first meal which often consists of small lizards, frogs and rodents.

In the graphic shown below, small nodules are present along the anacondas belly region, suggesting
that they probably had legs at one time.

The anaconda is not on any endangered list although it faces many threats from hunters who use
the giant snake's skin to make handbags, clothing, belts, and shoes.  Anacondas also face the
shrinking of its rainforest habitat as well as human intrusion and pollution caused by traffic and
factories in the large cities of South America.  Thanks to the Convention on International Trade
and Endangered Species of Wild Fauna and Flora (CITES), laws are being enacted to protect
this snake species and to make sure the anaconda will be around for many more years.

Below, shaded in red is the area of the world where the giant anaconda is found.

Check back next month for October's "Creature of the Month"  The Ostrich.

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