Head to head
Anaconda vs Boa Constrictor
Anacondas and boa constrictors are both boas, both South American, both constrictors, and both often called simply boas, which keeps the confusion going. One is a medium-sized generalist, the other is the heaviest snake alive.
| Anaconda | Boa Constrictor | |
|---|---|---|
| What it is | Genus Eunectes, four species | One species, Boa constrictor |
| Typical length | Green anaconda: 3 to 6 m | 2 to 3 m |
| Weight | Up to 70 to 100+ kg (green anaconda) | Usually 10 to 15 kg |
| Habitat | Swamps, rivers, flooded grassland | Forest, scrub, and farmland |
| Lifestyle | Semi-aquatic ambush hunter | Ground-dwelling and climbing |
| Venom | None; kills by constriction | None; kills by constriction |
| Young | Live birth, 20 to 40 young | Live birth, 10 to 60 young |
| In captivity | Uncommon; large and demanding | Very common pet snake |
Anaconda vs Boa Constrictor: common questions
Is an anaconda a kind of boa?
Yes. Both the anaconda and the boa constrictor are members of the boa family, Boidae, a group of non-venomous, live-bearing constrictors found mainly in the Americas. In everyday speech people often shorten boa constrictor to just boa, which makes it sound as though the boa constrictor is the boa and the anaconda is something else, but strictly the anaconda is also a boa. The anacondas are simply the large, semi-aquatic boas of the genus Eunectes, while the boa constrictor is one particular terrestrial species.
Which is bigger, an anaconda or a boa constrictor?
The anaconda, by a wide margin, if you mean the green anaconda. A large green anaconda is two to three times the length of a typical boa constrictor and can weigh five to ten times as much, with a body as thick as a grown adult thigh. The smaller anaconda species, such as the yellow anaconda at around 3 metres, are closer to a large boa constrictor in length but still heavier-built. A boa constrictor rarely exceeds about 3.5 metres and is a comparatively slender, manageable snake.
Are either of them dangerous to keep or encounter?
A boa constrictor is a standard pet-trade species, and while a large adult is strong and a careless feeding can result in a bite, it is not considered dangerous to a sensible keeper and there are no reliable records of a boa constrictor killing a person. Green anacondas are a different proposition in captivity, being huge, heavy, water-loving, and strong enough that keepers are advised never to handle a large one alone, but even so, documented human deaths from wild or captive anacondas are essentially absent. Both snakes will bite defensively if cornered, and a big constrictor should always be treated with respect, but the jungle-adventure image of either hunting people is fiction.