As Earth’s largest tropical wilderness, the Amazon is home to more species than anywhere else. The large predators and iconic animals that roam this expansive forest include the famous jaguar, black caiman, and Amazon jungle anaconda, a fascinating snake surrounded in mystery.
Chancing upon these giant snakes is a fantastic experience in the Amazon especially while canoeing through the swamps or flooded forest. Unless threatened, anaconda are not likely to attack and instead prefer swimming away to find a quieter area to rest.
Reptiles are one of the oldest animal groups and have lived in the Amazon since it first formed around 55 million years ago. Today, one of the largest groups of reptiles are the snakes with around 3,000 different species, which live on every continent except Antarctica. There are a fantastic diversity of Amazon Rainforest snakes with diverse colors and behaviors. These include the very attractive rainbow boas, emerald tree boas, whip snakes, and coral snakes. The most famous snake, and an icon of the Amazon Rainforest, is the anaconda, which refer to snakes of the genus Eunectes and more often specifically to the green anaconda, Eunectes murinus.
Famous as a giant of the Amazon, the green anaconda is the world’s heaviest snake and one of the world’s longest, second only in length the the less robust reticulated python. The females reach a larger body size than males and cannibalism among the snakes is reported, often where the females eat the male.
Similar in behavior to pythons, anacondas are members of the boa group of snakes (Boidae) and share some similar characteristics with the pythons. Both groups have a vestigial pelvic bone, lack venom, and use constriction to kill their prey. Boas then have a few differences, such as lacking postfrontal bones in their skulls and giving birth to live young. Despite these differences, both the python and boa groups contain some of the largest snakes on Earth.
Anaconda range across South America from the north to as far south as Paraguay, but are mainly found in the Amazon and Orinoco basins. These Amazon Rainforest animals prefer slow moving water or swamps and marshes. Although they find it difficult to move on land, anaconda are graceful swimmers and are adapted with their eyes and nasal openings atop their heads to conceal themselves under the water to ambush prey. Their bodies have an olive-green color with oval spots down their body and a yellow underside. This camouflages them perfectly in murky Amazonian waters as they wait for an unsuspecting animal to approach the water.
Anaconda are mainly nocturnal and use their senses to search for a range of food, including capybara, fish, birds, deer, tapir, and caiman. They can unhinge their lower jaws and stretch their bodies to swallow prey whole. Because of the large size of their prey, anaconda can go months without a single meal. When ambushing land-living prey, anaconda strike from the water’s edge using their backward facing teeth to lock onto the animal’s flesh. They then constrict their prey to limit circulation and cut off blood flow to the heart and brain. Previously, constrictors were thought to kill by suffocating the animal, but new research suggests otherwise.
After being born live among around 30 or so siblings, young anaconda are only 3 feet long and are preyed upon by a range of animals. If they manage to escape capture, anacondas of this size feed on small prey like insects then move on to fish and rodents as they grow. They can live for around 30 years and during this time reach 500 times their birth weight. By this stage, they have moved onto the larger prey species of capybara, deer and tapir.
Like many animals, habitat loss is a major threat to anaconda as their forests are cleared and wetlands turned to agricultural land. They are also hunted for their skins, but because of low human populations throughout their main habitat they are not regarded as threatened. However, because of many myths and misinformation, some locals regard anaconda as very dangerous and kill them on site. Although potentially posing a threat to infants, anaconda pose little threat to adults.
Because of their preference to remain submerged, anaconda are difficult to see in the high water season. This is when the Amazon River and rainforest floods and the snakes can easily conceal themselves and swim away. The dry season is a much better time for viewing anaconda to maximise your chances as there is less water to hide in. Aside from the rainforests, other great places for viewing anaconda are the wetlands, such as the Pantanal in Brazil and Paraguay, Argentina’s Iberá Wetlands, and Venezuela’s Los Llanos.
Books on Wildlife
Here is a selection of good books and guides on wildlife to help you learn more about animals and plants in their natural environment.