Boa

Boa, common name for non-poisonous snakes of the same family as the pythons. Like all members of this family, boas are constrictors—that is, they kill their prey by squeezing it to death and then swallowing it whole. They can stretch their jaws wide apart to swallow animals larger than their heads; but, while a large boa might easily kill an average-size person, it would have difficulty swallowing the body, and is generally not considered a threat to humans. Depending on the size of its prey, a boa may take days or even weeks to digest its food. Many of the exceptionally large snakes of the world are of this family, but not all boas are large. Some are no more than 50 cm (20 in) long when fully grown. Boas vary greatly in colour and pattern.

There are about 8 genera and 39 species of boas, characterized by well-developed hip bones and by vestigial hind legs, which can be seen externally as a pair of movable spurs. Boas and pythons differ in several ways, primarily in the skeleton. Boas give birth to live young, whereas pythons lay eggs; pythons are confined mostly to Eurasia, whereas boas are found worldwide.

Probably the best-known boa is the boa constrictor, found in the jungles of Central and South America. Boa constrictors are usually yellowish or greyish, with a pattern of dark brown dorsal “saddles”; the tail is often reddish-orange. Most adults do not exceed 2 to 3 m (6.5 to 10 ft) in length, but unusually large individuals may reach 4m (13 ft). Stories of larger boas may have caused boa constrictors to be confused with anacondas (water boas) or with the pythons of Asia.

Tree boas, such as the brightly coloured emerald tree boa, live in trees and have strong, prehensile tails. With their triangular heads, elliptical eye pupils, and long, curved front teeth, they resemble the venomous vipers.

Some smaller boas, such as the rubber boa, range throughout much of the north-western United States. Found as far north as British Columbia, Washington, and Montana, the rubber boa, whose shiny brown skin actually resembles rubber, is a burrowing animal. Because of its blunt head and tail, it is sometimes called a two-headed snake.

Scientific classification: Boas belong to the family Boidae. The boa constrictor is classified as Boa constrictor, the emerald tree boa as Corallus canina, and the rubber boa as Charina bottae.