Boa

Boidae
Boa constrictor, Boa constrictor
Scientific classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Reptilia Order: Squamata Suborder: Serpentes Infraorder: Alethinophidia Family: Boidae Gray, 1825
Synonyms
Boidae - Gray, 1825

-Boa is the common name for any of the various non-venomous, live-bearing constricting snakes comprising the family Boidae, characterized by stout bodies, two functional lungs, vestiges of hind limbs, and, unlike the similar, but egg-laying, pythons (family Pythonidae), lacking the postfrontal bones and premaxillary teeth. Well-known boas include the anacondas and boa constrictors.

The term boa also is used more specifically for any of the members of the subfamily Boinae, the "true boas," and as the genus name, Boa, within the Boinae subfamily. The Boinae subfamily is one of two subfamilies within Boidae.

Found in both the Old World and New World, boas inhabit terrestrial, semi-aquatic, and arboreal habitats. They are integral to food chains in these areas, ambushing and constricting their diverse prey of birds, amphibians, fish, reptiles (lizards, caimans), and mammals (rodents, opposums, monkeys, capybaras, tapirs, and deer, etc.), and being preyed upon by jaguars, caimans, and small or younger boas by birds of prey.

Other snakes outside of the Boidae family also have the common name of boa. These include any member of the Bolyeriidae, Round Island boas, a small family of non-venomous snakes from Mauritius and nearby islands, known as "Round Island boas," and any member of the Tropidophiidae, a family of non-venomous snakes found in Central America, South America and the Caribbean and known as "dwarf boas."

Boidae

The Boidae are a family of non-venomous snakes found in the Americas, Africa, Europe, Asia and some Pacific Islands. Relatively primitive snakes, adult boas (or boids) are medium to large in size, with females usually larger than the males. Two subfamilies comprising eight genera and 43 species are currently recognized (ITIS 2004).

Boas are similar in appearance and closely related to pythons, the common name for a group of non-venomous constricting snakes comprising the family Pythonidae. Both boas and pythons are considered to be primitive snakes, and both are constrictors that suffocate their prey by wrapping around it. Both also have two lungs (most snakes have one lung) and have remnants of hind legs and pelvic bones (SDZ 2007). Both pythons and boids have elongated supratemporal bones. The quadrate bones are also elongated, but not as much, while both are capable of moving freely so that when they swing sideways to their maximum extent, the distance between the hinges of the lower jaw is greatly increased (Parker and Grandison 1977).

Both families, the pythons and boas, share a number of primitive characteristics. Nearly all have a relatively rigid lower jaw with a coronoid element, as well as a vestigial pelvic girdle with hind limbs that are partially visible as a pair of spurs, one on either side of the vent. In males, these anal spurs are larger and more conspicuous than in females. A long row of palatal teeth is present and most species have a functional left lung that can be up to 75% as large as the right lung (VMNH).

Pythons are distinguishable from boas in that pythons have teeth on the premaxilla, a small bone at the very front and center of the upper jaw, and boas lack the postfrontal bones of the pythons. Furthermore, while most boas produce live young, pythons produce eggs. When labial pits are present, these are located between the scales as opposed to on them. Also, their geographical distributions are almost entirely mutually exclusive. In the few areas that they do coexist, the tendency is for them to occupy different habitats (VMNH).

However, pythons and boas are similar enough that some authorities actually place pythons as a subfamily (Pythoninae) within the boa family. Some species of sand boas (Ericinae) are also called python.

Geographic range

Found in Northern, Central and South America, the Caribbean, southeastern Europe and Asia Minor, Northern, Central and East Africa, Madagascar and Reunion Island, the Arabian Peninsula, Central and southwestern Asia, India and Sri Lanka, the Moluccas and New Guinea through to Melanesia and Samoa.

It used to be said that boas are found in the New World and pythons in the Old World, but with boid species found on Madagascar, Fiji and the Solomon Islands, this is not quite true. Instead, it seems that they have survived in evolutionarily isolated areas. After all, South America had, until a few million years ago, a distinct fauna that included marsupial and mammals. With the land bridge to North America, boids have migrated north as placental mammals and colubrids have migrated south. The semi-aquatic anacondas are limited to the New World (South America).

Feeding and reproduction

Prey is killed by a process known as constriction; after an animal has been grasped to restrain it, a number of coils are hastily wrapped around it. Then, by applying and maintaining sufficient pressure to prevent it from inhaling, the prey eventually succumbs due to asphyxiation. It has recently been suggested that the pressures produced during constriction cause cardiac arrest by interfering with blood flow, but this hypothesis has not yet been confirmed.

Larger specimens usually eat animals about the size of a house cat, but larger food items are not unknown: the diet of the common anaconda, Eunectes murinus, is known to include subadult tapirs. Prey is swallowed whole, and may take anywhere from several days or even weeks to fully digest. Despite their intimidating size and muscular power, they are generally not dangerous to humans.

Contrary to popular belief, even the larger species do not crush their prey to death; in fact, prey is not even noticeably deformed before it is swallowed. The speed with which the coils are applied is impressive and the force they exert may be significant, but death is caused by suffocation, with the victim not being able to move its ribs in order to breathe while it is being constricted.

Most species are ovoviviparous, with females giving birth to live young. This is in contrast to the pythons, which all lay eggs (oviparous).

Subfamilies

Subfamily	Taxon author	Genera	Species	Common name	Geographic range
Boinae	Gray, 1825	5	28	True boas	Central and South America, Africa, Madagascar, Reunion Island, Mauritius, the Maluku Islands and New Guinea.
Erycinae	Bonaparte, 1831	3	15	Old World sand boas	South and southeastern Europe, Asia Minor, north, central, west and east Africa, Arabia, central and southwestern Asia, India, Sri Lanka. Also in southwestern Canada, the western United States and northwestern Mexico.

Type genus = Boa - Gray, 1825

Taxonomy

Pythons are sometimes classified as a subfamily of Boidae, the Pythoninae, but are in this case listed under their own family, the Pythonidae. In the same way, the Old World sand boas, the Erycinae, are also frequently listed under their own family, the Erycidae.

Boinae

Common names: boas.

The Boinae are a subfamily of non-venomous boas found in Central and South America, Africa and Southeast Asia. Five genera comprising 28 species are currently recognized.

Found in Central and South America, Africa, Madagascar, Reunion Island, Mauritius, the Maluku Islands and New Guinea.

Genera

Genus	Taxon author	Species	Subsp.*	Common name	Geographic range
BoaT	Linnaeus, 1758	4	9	Boas	Mexico, Central America, South America, Madagascar and on Reunion Island.
Candoia	Gray, 1842	4	2	Bevel-nosed boas	from Samoa and Tokelau west through Melanesia to New Guinea and the Maluku Islands.
Corallus	Daudin, 1803	7	2	Neotropical tree boas	Central America, South America and the West Indies. In Central America they occur in Honduras, eastern Guatemala through Nicaragua, Costa Rica and Panama. Its range in South America includes Pacific Colombia and Ecuador, as well as the Amazon Basin from Colombia, Ecuador, Peru and northern Bolivia through Brazil to Venezuela, Isla Margarita, Trinidad, Tobago, Guyana, Suriname and French Guiana. In the West Indies it is found on St. Vincent, the Grenadines (Bequia Island, Ile Quatre, Baliceaux, Mustique, Canouan, Maryeau, Union Island, Petit Martinique and Carriacou), Grenada and the Windward Islands (Lesser Antilles).
Epicrates	Wagler, 1830	10	21	Rainbow boas	Lower Central America through South America as far south as Argentina, as well as in the West Indies.
Eunectes	Wagler, 1830	3	1	Anacondas	Tropical South America from Colombia and Venezuela south to Argentina.

*) Not including the nominate subspecies.
^T) Type genus.

Taxonomy

Some sources also include the genera Acrantophis and Sanzinia, which are synonymized here with the genus Boa.

Boa (genus)

Common names: boas, boa constrictors.

Boa is a genus of non-venomous boas found in Mexico, Central and South America, Madagascar and on Reunion Island. Four species are currently recognized.

Description

The largest member of this group, B. c. constrictor, has been reported to grow to a maximum size of 18 feet (5.5 m) in length, although some believe that particular specimen was misidentified. It has an interesting color pattern of brown and black with a red tail. Feeding on birds and small mammals, it does well in captivity, tames easily and is a common sight in zoos and homes.

Geographic range

Found in Mexico, Central America, South America, Madagascar and on Reunion Island.

Species

Species	Taxon author	Subsp.*	Common name	Geographic range
B. constrictorT	Linnaeus, 1758	9	Boa constrictor	Northern Mexico through Central America (Belize, Guatemala, Honduras, El Salvador, Nicaragua, Costa Rica and Panama) to South America north of 35°S (Colombia, Ecuador, Peru, Venezuela, Guyana, Suriname, French Guiana, Brazil, Bolivia, Uruguay and Argentina. Also in the Lesser Antilles (Dominica and St. Lucia), on San Andrés, Providencia and many other islands along the coasts of Mexico and Central and South America.
B. dumerili	(Jan In Jan & Sordelli, 1860)	0	Duméril's boa	Madagascar and Reunion Island.
B. madagascariensis	(Duméril & Bibron, 1844)	0	Madagascar ground boa	Madagascar.
B. manditra	Kluge, 1991	0	Madagascar tree boa	Madagascar.

*) Not including the nominate subspecies.
^T) Type species.

Taxonomy

Although four are currently placed in this genus, B. constrictor is not considered to be closely related to the other three. Consequently, the latter are often moved to other genera, particularly Acrantophis and Sanzinia. Nevertheless, all are commonly known as "boa constrictors". To add further to the naming confusion, many species of snake in Boidae are known as "boas" and all are constrictors. Also, more than a few subspecies of B. constrictor are recognized, several of which have distinct common names.

See also

• List of boine species and subspecies
• Boinae by common name
• Boinae by taxonomic synonyms

References

ISBN links support NWE through referral fees

2004. http://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&search_value=174321 Boidae Gray, 1825 Taxonomic Serial No.: 174321

• San Diego Zoo (SDZ). 2007. Reptiles: Boa. San Diego Zoo's Animal Bytes. Retrieved August 22,2007.

Virtual Museum of Natural History (VMNH). n.d. .

Parker HW, Grandison AGC. 1977. Snakes — a natural history. Second Edition. British Museum (Natural History) and Cornell University Press. 108 pp. 16 plates. LCCCN 76-54625. ISBN 0-8014-1095-9 (cloth), ISBN 0-8014-9164-9 (paper).</ref>

McDiarmid RW, Campbell JA, Touré T. 1999. Snake Species of the World: A Taxonomic and Geographic Reference, vol. 1. Herpetologists' League. 511 pp. ISBN 1-893777-00-6 (series). ISBN 1-893777-01-4 (volume).

Further reading

• Kluge AG. 1991. Boine Snake Phylogeny and Research Cycles. Misc. Pub. Museum of Zoology, Univ. of Michigan No. 178. 58 pp. PDF at University of Michigan Library. Accessed 11 July 2008.
• Vences M, Glaw F, Kosuch J, Böhme W, Veith M. 2001. Phylogeny of South American and Malagasy Boine Snakes: Molecular Evidence for the Validity of Sanzinia and Acrantophis and Biogeographic Implications. Copeia No 4. p. 1151-1154. PDF at Miguel Vences. Accessed 29 August 2008.
• Vences M, Glaw F. 2003. Phylogeography, systematics and conservation status of boid snakes from Madagascar (Sanzinia and Acrantophis). Salamandra, Reinbach, 39(3/4): p. 181-206. PDF at Miguel Vences. Accessed 29 August 2008.

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