Boidae

The Boidae, commonly known as boas or boids, are a family of nonvenomous snakes. They live in many parts of the world, including the Americas, Africa, Europe, Asia, and some Pacific islands.

Most boa snakes are medium to large in size. Usually, the females are bigger than the males. Scientists have identified six subfamilies and many different genera and species within this group.

Boas are interesting because they are strong and powerful. They do not use venom to catch their food. Instead, they wrap their bodies around their prey to hold it tightly.

The green anaconda from South America is one of the heaviest and second-longest snakes known.

Description

Boas are a type of snake, similar to pythons. They have long bones on the sides of their heads and flexible jaw joints that let them open their mouths wide. Boas and pythons share some traits, like a stiff lower jaw and small hind limb spurs that are more noticeable in males. Most boas have teeth on the roof of their mouths and a functional left lung.

Cloaca region of a Boa constrictor with spurs (rudimentary hindlegs)

Unlike pythons, boas do not have certain bones in their skulls and they give birth to live babies. When they have special sensing pits on their faces, these pits sit between their scales. Boas are found in many parts of the world, including the Americas, Africa, Europe, Asia, and some Pacific islands. They live in different areas than pythons, often preferring unique habitats.

Distribution and habitat

Most boas live in North, Central, and South America, and also in the Caribbean. A few live in southeastern Europe and Asia Minor, North, Central and East Africa, Madagascar, the Arabian Peninsula, Central and Southwestern Asia, India and Sri Lanka, Indonesian islands (Moluccas, West Papua, Talaud, Sulawesi) and Papua New Guinea through Melanesia and Samoa.

Feeding

Boas catch their food by wrapping around it. They squeeze the animal until it can’t breathe anymore, and then it stops moving.

Big boas can eat animals about the size of a house cat, or even bigger! They swallow their food whole, which can take many days or weeks to digest. Boas are not dangerous to people. They don’t hurt their food; the food just stops breathing while being held tightly.

Reproduction

Most boas are born live. The mother gives birth to live babies instead of laying eggs. This is different from pythons, which lay eggs to have their babies.

Subfamilies

Type genus = Boa – Gray, 1825

Subfamily	Taxon author	Genera	Species	Common name	Geographic range
Boinae	Gray, 1825	5	34	true boas	Central and South America and the West Indies
Calabariinae	Gray, 1858	1	1	Calabar python	tropical West and Central Africa
Candoiinae	Pyron, Burbink & Wiens, 2013	1	5	bevel-nosed boas or keel-scaled boas	from Sulawesi through the Maluku Islands, New Guinea and Melanesia to Samoa and Tokelau
Erycinae	Bonaparte, 1831	3	18	Old World sand boas	Southern and Southeastern Europe, Asia Minor, North, Central, West and East Africa, Arabia, Central and Southwest Asia, India, Sri Lanka, western Canada, the western United States, and northwestern Mexico
Sanziniinae	Romer, 1956	2	4	Madagascan boas or Malagasy boas	Madagascar
Ungaliophiinae	McDowell, 1987	2	3	neotropical dwarf boas	Central and South America from southern Mexico to Colombia

Taxonomy

Pythons used to be part of the boa family, but scientists found they are not closely related to boas, even though they look similar.

Most non-boa boids are now in their own families, like Calabariidae, Candoiidae, Charinidae, Erycidae, Sanziniidae, and Ungaliophiidae. Scientists have debated how to classify boid snakes for a long time. Deciding which group a boid snake belongs to is sometimes a choice.

The Ungaliophiinae subfamily used to have four groups of snakes. Two of these (Tropidophis and Trachyboa) are more closely related to the American pipe snake (Anilius scytale) and are now in the family Tropidophiidae. The other two groups (Ungaliophis and Exiliboa) are related to the Charina/Lichanura group in the boa family.