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Boidae

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The Boidae are a large family of nonvenomous snakes. People commonly refer to them as boas or boids. These snakes are famous for their impressive size and muscular strength. The green anaconda is a well-known member of this family. It is the heaviest snake in the world. It is also the second-longest snake known to science. Most adult boas are medium to large in size. In many species, the females grow larger than the males.

Boas use a method called constriction to hunt their prey. First, the snake must grasp an animal to restrain it. The snake then quickly wraps several coils around the victim. By maintaining steady pressure, the snake prevents the prey from inhaling. This leads to death by asphyxiation, which is suffocation. Some scientists have suggested that this pressure might cause cardiac arrest. This would happen by interfering with the prey's blood flow. However, this specific hypothesis has not been confirmed yet.

Rudimentary hindlegs spurs in Boa constrictor snake
Rudimentary hindlegs spurs in Boa constrictor snake

Even though they are powerful, boas do not crush their prey. The prey is not noticeably deformed before the snake swallows it. Large specimens often eat animals roughly the size of a domestic cat. The green anaconda is capable of eating even larger items, such as subadult tapirs. Once caught, the prey is swallowed whole. It can take several days or even weeks for the snake to fully digest a meal.

Rudimentary hindlegs spurs in Boa constrictor snake
Rudimentary hindlegs spurs in Boa constrictor snake

Physically, boas possess several unique anatomical features. They have elongated supratemporal bones in their heads. They also have elongated quadrate bones that move freely. This movement allows the hinges of the lower jaw to spread wide. This helps them swallow large prey. Most boas also have a long row of palatal teeth on the roof of their mouth. Many species have a functional left lung. This lung can be up to 75% the size of the right lung.

Rudimentary hindlegs spurs in Boa constrictor snake
Rudimentary hindlegs spurs in Boa constrictor snake

Boas also show signs of their evolutionary history through their bodies. Most species have a vestigial pelvic girdle. This is a leftover structure from ancestors that had legs. This results in a pair of small spurs near the vent. These spurs are rudimentary hind limbs. In males, these anal spurs are usually larger and more conspicuous than in females.

Rudimentary hindlegs spurs in Boa constrictor snake
Rudimentary hindlegs spurs in Boa constrictor snake

Taxonomy, the science of naming and classifying life, shows that boas are distinct from pythons. While they look similar, they have different reproductive methods. Pythons are oviparous, meaning they lay eggs. Most boas are ovoviviparous, which means they give birth to live young. Boas also lack postfrontal bones and premaxillary teeth. Their geographical distributions are also almost entirely mutually exclusive. If they do live in the same area, they usually occupy different habitats.

Boavus idelmani
Boavus idelmani

History explains how boas spread across the globe. South America was isolated for a long time. This allowed unique animals to develop there. About three million years ago, the Panamanian land bridge formed. This connected North and South America. During the Great American Interchange, boines migrated north. At the same time, other animals migrated south.

Boavus idelmani
Boavus idelmani

Today, scientists recognize six subfamilies within Boidae. These include Boinae, which are the true boas of the Americas. Other groups include the Calabariinae of Africa and the Erycinae of the Old World. There are also the Candoiinae, Sanziniinae, Ungaliophiinae, and others. Currently, there are between 54 and 67 recognized species. These species live in diverse places, from the Caribbean to Indonesia and Papua New Guinea.

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