Anacondas are the heaviest snakes in the world. They live in water and slither unnoticed along the riverbed using their colouring as camouflage.
Amazing Facts About the Anaconda
Anacondas are the heaviest, if not the largest, snakes in the world, with records of individuals stretching up to 12 m long and weighing up to 250 kg. They are semi-aquatic snakes living in the tropical habitat of South America and feeding on a range of species, including tapirs and caimans.
How many species of Anaconda are there?
There are four different species of anaconda: the green anaconda (the species that most people mean when they speak about Anacondas), the yellow anaconda, the dark-spotted anaconda and the Bolivian anaconda. These species can be distinguished from other species of boa snakes because they lack a particular bone called the supraorbital bone, which is usually found above the eye socket.
What does an anaconda look like?
Green anacondas have huge bodies covered in small olive-green scales, with smooth black ovals along their backs and yellowish stomachs. Compared to their huge bodies, anacondas have relatively small heads, with their eyes and nostrils positioned on top, an adaptation that allows them to lie hidden underwater. Only the top of their head shows above the surface. Green Anacondas also have a noticeable black stripe that runs from the eye to the jaw. Males are typically smaller than females and have claw-like spurs on their lower bodies, which they use to hold onto females during mating. Interestingly, these claws are believed to be the historical remnants of a hind limb! Like all snakes, anacondas have a forked tongue, which they use to locate prey and potential mates.
Where do anacondas live?
Anacondas are found throughout South America, where they spend the majority of their time in the shallow waters of open wetlands such as the Amazon River Basin, the Orinoco Basin in Columbia and the Llanos grasslands in Venezuela. There are instances of captive anacondas escaping and surviving further afield, with reports of native Florida species such as alligators and bobcats declining due to competition for food with non-native anacondas.
How do Anacondas move?
All snakes move by contracting the muscles between the scales on the undersides of their bodies, undulating themselves across land or through water. A large number of vertebrae linked flexibly together allow them to bend and coil in every direction.
What does an anaconda eat?
Green anacondas are not venomous. They kill their prey by constriction, holding the animal in place with their sharp teeth (curved backwards to allow them a better grip) while squeezing their massive bodies around their victim until they suffocate. Their coils are powerful enough to kill animals the size of a horse or a fully-grown black caiman. And stretchy ligaments in their jaws mean they can open their mouths wide enough to swallow them.
Anacondas are opportunistic ambush predators. They lie hidden underwater (camouflaged by their dark colouring) until an animal approaches the water’s edge to drink, at which point they strike! As anacondas typically hunt near water, their prey often drowns before constriction is complete. Once the animal is dead, the anaconda will release its coils and ingest its prey headfirst (to reduce any obstruction caused by the limbs) and whole!
Green Anacondas are most active in the early evening and will eat anything they can swallow, including fish, reptiles such as turtles, amphibians, birds and mammals like capybaras and peccaries. Feeding on such large prey can be dangerous and occasionally leads to serious injuries. But, the danger may be worth the risk, as large anacondas can survive without eating for months after such a large meal.
Do Anacondas hibernate?
Anacondas do not hibernate, but those living in areas of seasonal flooding may undergo a period of dormancy where they bury themselves in mud for the duration of the dry period. Anacondas are very adaptable, and many will migrate large distances to find other sources of water, while those living near a constant water source, such as a river basin, will be active throughout the year. Male anacondas may also migrate in search of females but will return to their own foraging grounds after the breeding season.
How do Anacondas sense the world around them?
Most reptiles, including anacondas, are poikilotherms. This means they are unable to regulate their own body temperature. They must therefore use external means, such as basking in the sun to warm themselves up or hiding underwater to cool themselves down. Green anacondas, like all snakes, have no external ears but instead, detect their prey using the vibrations created by their movement, the chemicals in the air (using their forked tongues and a special organ called the Jacobson’s, which is a patch of sensory cells within the nasal chamber) and their heat signature (anacondas have pit organs along their upper lip that sense infrared radiation). Snakes do not have eyelids like we do – a single clear scale protects their eyes.
When do anacondas breed?
Green Anacondas are polyandrous, which means a female will mate with several different males. Mating occurs during the dry season (March to May) and lasts for several weeks.
Breeding is quite the spectacle as many males surround a female in a giant tangle of snakes called a ‘breeding ball’. However, female anacondas are selective about their mates and appear to prefer larger males, possibly because she is likely to eat them afterwards. Scientists believe this is a behaviour that helps her survive gestation, as she doesn’t eat for up to seven months.
Like other species of boa snakes, female anacondas do not lay eggs. They give birth to anywhere between 4 and 80 live young (the average clutch size is 20–40), which are around 60 cm long when born. A newly born anaconda increases its mass 500 times by the time it reaches adulthood. Once born, young anacondas are completely independent and receive no parental care. Female anacondas typically breed in alternate years, allowing them to regain the energy lost during reproduction.
What are the threats to anacondas?
Depending on the size of the anaconda, predators include caiman and jaguar, particularly during the dry season when other sources of prey may be scarce. Small anacondas are, therefore, extremely aggressive and frequently bite. They may hide from predators in mud or water but, when attacked, will curl into a tight ball, striking out and emitting a strong odour in an attempt to drive away the predator.
Other threats include the exotic pet trade, where young snakes are taken from the wild to be sold as pets, and conflict with humans. On rare occasions, they have killed humans, but attacks are rare, largely due to the low numbers of humans living in anaconda habitat. However, the indigenous people of Brazil and Peru believe the green anaconda has spiritual and medical properties and use their fat as a treatment for conditions including rheumatism and asthma. Conflict is also likely to increase as humans encroach on anaconda territory through an increase in farmland and settlement. The wetlands and swamps in which anacondas live are increasingly threatened by wildfires and by the spread of agricultural land.
How can you help an Anaconda?
The conservation status of anacondas is currently unknown, with very few projects specifically dedicated to this species. However, like many other species living in rainforests, deforestation, forest fires, and climate change threaten their habitat. There are many ways in which you can help, including becoming a member of charities like WWF that work with local governments and businesses to improve conservation of the rainforests. You can also help spread the word about the challenges faced by anacondas and other rainforest species via social media. Alternatively, contact your local government representative to encourage them to take stronger action in the fight against climate change.
When on holiday, never purchase any products or souvenirs made from animals (including snakeskin), or support cruel exhibitions of captive animals, which have often been taken from their homes in the wild. Green anacondas may be large, powerful and terrifying to many humans, but they have no interest in us, and as long as we leave their habitat alone, there is no reason why there should be a conflict between humans and anacondas.
Page updated May 2023 by OneKind volunteer Ami Patrick.