- Common names: boas, boids.
The Boidae are a family of nonvenomous snakes found in America, Africa, Europe, Asia and some Pacific Islands. Relatively primitive snakes, adults are medium to large in size, with females usually larger than the males. Two subfamilies, comprising eight genera and 43 species, are currently recognized.
Like the pythons, boas 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.
Both families 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.
Boids are, however, distinguished from the pythons in that none have postfrontal bones or premaxillary teeth, and that they give birth to live young. 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.
It used to be said that boas are found in the New World and pythons in the Old World, but with boid species present in Madagascar, Fiji and the Solomon Islands, this is not quite accurate; instead, it seems they have survived in evolutionarily isolated areas. South America was isolated until a few million years ago, with a fauna that included marsupials and other distinctive mammals. With the formation of the Panamanian land bridge to North America about three million years ago, boids have migrated north as colubrids (and various Nearctic mammals) have migrated south, as part of the Great American Interchange.
They are 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.
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. Recently, the pressures produced during constriction have been suggested as the cause of 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 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 to breathe while it is being constricted.
|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.|
Pythons were 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. Additionally, morphological studies place the subfamily Ungaliophiinae in Tropidophiidae, whereas all molecular analyses place them as sister group of Charina-Lichanura clade, within Boidae.
- List of boine species and subspecies
- List of erycine species and subspecies
- Boidae by common name
- Boidae by taxonomic synonyms
- List of snakes, overview of all snake families and genera.
|Wikimedia Commons has media related to: Boidae|
- 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).
- "Boidae". Integrated Taxonomic Information System. Retrieved 14 July 2008.
- 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).
- Boidae at VMNH. Accessed 15 July 2008.
- Mehrtens JM (1987). Living Snakes of the World in Color. New York: Sterling Publishers. ISBN 0-8069-6460-X. [page needed]
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