All About Boas

Scientific name: Boidae

Emerald tree boa - Corallus caninus
Morgan Rauscher / Shutterstock

Boas (Boidae) are a group of nonvenomous snakes that include about 36 species. Boas are found in North America, South America, Africa, Madagascar, Europe and many Pacific Islands. Boas include the largest of all living snakes, the green anaconda.

Other Snakes Called Boas

The name boa is also used for two groups of snakes that do not belong to the Boidae family, the split-jawed boas (Bolyeriidae) and the dwarf boas (Tropidophiidae). The split-jawed boas and the dwarf boas are not closely related to members of the family Boidae.

Anatomy of Boas

Boas are considered to be somewhat primitive snakes. They have a rigid lower jaw and vestigial pelvic bones, with small remnant hind limbs that form a pair of spurs on either side of the body. Although boas share many characteristics with their relatives the pythons, they differ in that they lack postfrontal bones and premaxillary teeth and they give birth to live young.

Some but not all species of boas have labial pits, sensory organs that enable the snakes to sense infrared thermal radiation, an ability which is useful in the location and capture of prey but which also provides functionality in thermoregulation and detection of predators.

Boa Diet and Habitat

Boas are predominantly terrestrial snakes that forage in low lying bushes and trees and feed on small vertebrates. Some boas are tree-dwelling species that stalk their prey by hanging their head down from their perch amongst the branches.

Boas capture their prey by first grasping it and then coiling their body quickly around it. Prey is then killed when the boa constricts its body tightly so that the prey cannot inhale and dies of asphyxiation. The diet of boas varies from species to species but generally includes mammals, birds and other reptiles.

The largest of all boas, in fact, the largest of all snakes, is the green anaconda. Green anacondas can grow to lengths of over 22 feet. Green anacondas are also the heaviest known species of snake and may also be the heaviest squamate species as well.

Boas inhabit North America, South America, Africa, Madagascar, Europe and many Pacific Islands. Boas are often regarded solely as tropical rainforest species, but although many species are found in rainforests this is not true for all boas. Some species live in arid regions such as the deserts of Australia.

The vast majority of boas are terrestrial or arboreal but one species, the green anaconda is an aquatic snake. Green anacondas are native to the slow-moving streams, swamps, and marshes on the eastern slopes of the Andes Mountains. They also occur on the island of Trinidad in the Caribbean. Green anacondas feed on larger prey than most other boas. Their diet includes wild pigs, deer, birds, turtles, capybara, caimans, and even jaguars.

Boa Reproduction

Boas undergo sexual reproduction and with the exception of two species in the genus Xenophidion, all bear live young. Females that bear live young do so by retaining their eggs within their body give birth to multiple young at once.

Classification of Boas

The Taxonomic Classification of boas is as follows:

Animals > Chordates > Reptiles > Squamates > Snakes > Boas

Boas are divided into two subgroups which include the true boas (Boinae) and the tree boas (Corallus). True boas include the largest species of boas such as the common boa and the anaconda. Tree boas are tree-dwelling snakes with slender bodies and long prehensile tails. Their bodies are somewhat flat in shape, a structure that gives them support and enables them to stretch from one branch to another. Tree boas often rest coiled up in the branches of trees. When they hunt, tree boas hang their head down from the branches and coil their neck in an S-shape to give themselves a good angle from which to strike their prey below.

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Klappenbach, Laura. "All About Boas." ThoughtCo, Aug. 25, 2020, Klappenbach, Laura. (2020, August 25). All About Boas. Retrieved from Klappenbach, Laura. "All About Boas." ThoughtCo. (accessed March 20, 2023).