All snakes can swim, although some are better than others. One of the most powerful species alive today is the green anaconda ( Eunectes murinus). Perfectly at home in the rivers and swamps of the Amazon, it has eyes that face upward like a crocodile, allowing the creature to sweep muddy shores in search of prey – hiding its muscular coils beneath the surface of the water.
This is why anacondas are also called “water boas.” The shoe fits, or it would if they had feet. Besides the green anaconda, science recognizes three other species: the yellow anaconda, the black-spotted anaconda, and the Bolivian anaconda. All four belong to the boa family, and they are all originally from South America.
At every metric, the green anaconda stands out. He’s arguably the biggest snake in the world. However, trying to determine the maximum size of the animal poses many challenges.
The long and short of it
Amazonian folklore is full of stories about giant monster snakes ranging from 18.2 to 30.4 meters in length. The fossil record tells us that a colossal snake really slipped across the continent 60 million years ago. Named Titanoboa, it is said to have reached 15.2 meters in total length and weighed around 2.5 tons (2.26 metric tons).
Well, green anacondas are nowhere near that size. A common length for this species is around 19.7 feet (6 meters) – although males, being the smaller of the two sexes, rarely exceed 13.1 feet (4 meters). The largest anaconda ever reliably documented was 8.3 meters long.
Still, rumors of anacondas growing two or three times the size persist. Some of the claims are based on huge skins cut from dead snakes. The problem is, these are really easy to distort. Even if you don’t try.
Herpetologist William H. Lamar proved this point in 1978, when he killed a large wild anaconda. The freshly killed corpse measured a respectable length of 24.58 feet (or 7.49 meters). After skinning the reptile, Lamar measured its disembodied skin. Despite his best efforts, he couldn’t avoid stretching the skin as he worked, resulting in a post-mortem length of 10.54 meters (34.58 feet).
The largest and bulkier Eunectes murinus can weigh 200 kilograms or more. So, as a species, the green anaconda is considered the heaviest snake in the world – but not necessarily the longest.
Lengthwise, the Asian reticulated python likely beat it. According to Chris Mattison’s “The New Snake Encyclopedia,” there have been “several authenticated reports” of large “retics” measuring about 8.5 meters from end to end.
Anacondas have an affinity for slow-moving rivers, muddy swamps, and seasonally flooded plains. They rarely venture far from running or standing water – although some species may choose to hunt in forests on occasion.
Not only do snakes have eyeballs located at the top of their head, but the nostrils are located in this region as well. So a swimming or soaking anaconda can easily see and smell what is happening above the water. This makes the capture of prey much easier for these semi-aquatic reptiles.
Anacondas kill by constriction, using their jaws to grab the victim before immobilizing them with tightly coiled coils. Naturalists believed that snakes that used this technique actually strangled their prey. However, according to new research involving the red-tailed boa ( Boa constrictor), the real cause of death is cardiac arrest.
Wild anacondas feed on fish, lizards, birds, bird eggs, other snakes, carrion and a variety of mammals. Adults are known to swallow caimans: fiery crocodilians related to alligators. Another notable beast often taken by large anacondas is the capybara. The largest rodents on Earth, capybaras are herbivores with hairy legs that stand around 0.48 meters tall.
Being amphibious, they regularly cross anacondas. And mammals know how to fight: Older anacondas sometimes exhibit bite wounds left by the capybaras they attacked.
At this point, you’re probably wondering if people are on the menu. There is no doubt that a sufficiently large green anaconda could kill and eat a human. Yet no such incident has ever been confirmed.
That said, anacondas — like most creatures — will defend themselves if cornered. While none of these snakes are poisonous, they can inflict deep bites. Snakes can also secrete a foul-smelling liquid when in distress.
When the snakes have a ball
Among reptile breeders, anacondas are not as popular as red-tailed boas or large pythons. They need huge enclosures, high humidity levels, and water dishes large enough for snakes to use as soaking pools. Captive-bred individuals who have been handled their entire lives tend to be more docile than wild-caught anacondas. Even so, you shouldn’t get the anaconda of any species unless you are an experienced reptile hobbyist who understands large constrictors.
In 2012, the US Fish and Wildlife Service banned the import — and interstate transport — of the yellow anaconda. Growing up to 4.6 meters in length, this snake could potentially threaten all kinds of native species. And as the US Geological Survey reports, free-range yellow anacondas have been seen in Florida and Arkansas. These snakes were probably ancient pets.
Anacondas do not belong to the Everglades or the Arkansas Delta. But in their natural habitat, these reptiles are fascinating to watch. During the breeding season, several males may attempt to mate with a single female – at the same time. The result is a “breeding ball,” a pile of dogs that sees up to 13 loving males all squirming around an expectant mother.
Like most boas, anacondas give birth to live young, with litters containing anywhere from four to 82 baby snakes. And now we know that green anacondas don’t need mates to get pregnant. In 2014, a female kept in a British reptile park gave birth to three live babies even though she had never been kept with a male of her kind. An almost identical situation recently unfolded at the New England Aquarium.
Known as “parthenogenesis,” this style of asexual reproduction has also been observed in Komodo dragons and Burmese pythons.
Now it’s a cannibal.
Green anacondas have no qualms about cannibalism. In 2000, herpetologist Jesus Rivas noted four separate cases of Eunectes murinus eating one of his own. All of these incidents involved large females gobbling up smaller anacondas – at least two of which were males.