Bitis

Bitis
Scientific classification
Kingdom: Animalia Phylum: Chordata Subphylum: Vertebrata Class: Reptilia Order: Squamata Suborder: Serpentes Family: Viperidae Subfamily: Viperinae Genus: Bitis Gray, 1842
Synonyms
Cobra - Laurenti, 1768 Echidna - Merrem, 1820 Clotho - Gray, 1842 Bitis - Gray, 1842 Echidne - Duméril & Bibron, 1844 Hallowellius - Reus, 1939 Macrocerastes - Reus, 1939

Common names: puff adders, African adders, African vipers.  
 
Bitis is a genus of venomous vipers found in Africa and the southern Arabian Peninsula. It includes the largest and the smallest vipers in the world. Members are known for their characteristic threat displays that involves inflating and deflating their bodies while hissing and puffing loudly. The type species for this genus is B. arietans, which is also the most widely distributed viper is Africa. Currently, 14 species are recognized.

Description

Size variation within this genus is extreme, ranging from the very small B. schneideri, which grows to a maximum of 28 cm and is perhaps the world's smallest viperid, to the very large B. gabonica, which can attain a length of over 2 m and is the heaviest viper in the world.

All have a wide, triangular head with a rounded snout, distinct from the neck, and covered in small, keeled, inbricate scales. The canthus is also distinct. A number of species have enlarged rostral or supraocular scales that look like horns. The eyes are relatively small. They have large nostrils that are directed outwards and/or upwards. 0-6 rows of small scales separate the rostral and nasal scales. All species have a well-developed supranasal sac. The front of the maxillary bones are very short, supporting only one pair of recurved fangs.

These snakes are moderately to extremely stout. The body is covered with keeled scales that are imbricate with apical pits. At midbody, the dorsal scales number 21-46. Laterally, the dorsal scales may be slightly oblique. The ventral scales, which number 112-153, are large, rounded and sometimes have slight lateral keels. The tail is short. Anal scale single. The paired subcaudal scales number 16-37 and are sometimes keeled laterally.

Geographic range

Found in Africa and the southern Arabian Peninsula.

Behavior

Bitis species are known for their behavior of inflating and deflating their bodies in loud hissing or puffing threat displays. They are terrestrial ambush predators and appear sluggish, but can strike with amazing speed.

Reproduction

All members are viviparous and some give birth to large numbers of offspring.

Venom

All members of this genus are dangerous — some extremely so. At least six different polyvalent antivenoms are available. Five are produced by Aventis Pasteur (France), Pasteur Merieux (France) and SAIMR (South Africa). All of these specifically protect against B. arietans and four also cover B. gabonica. At least one protects specifically against bites from B. nasicornis: India Antiserum Africa Polyvalent. In the past, such antivenoms have been used to treat bites from other Bitis species, but with mixed results.

Species

Species	Authority	Subsp.*	Common name	Geographic range
B. arietansT	(Merrem, 1820)	1	Puff adder	Most of sub-Saharan Africa south to the Cape of Good Hope, including southern Morocco, Mauritania, Senegal, Mali, southern Algeria, Guinea]], Sierra Leone, Ivory Coast, Ghana, Togo, Benin, Niger, Nigeria, Chad, Sudan, Cameroon, Central African Republic, northern, eastern and southern DR Congo, Uganda, Kenya, Somalia, Rwanda, Burundi, Tanzania, Angola, Zambia, Malawi, Mozambique, Zimbabwe, Botswana, Namibia, South Africa. Also occurs on the Arabian peninsula, where it is found in southwestern Saudi Arabia and Yemen.
B. atropos	(Linnaeus, 1758)	0	Berg adder	Isolated populations in the mountainous areas of southern Africa: the Inyanga Highlands and Chimanimani Mountains of eastern Zimbabwe and nearby Mozambique, in South Africa along the Drakensberg Escarpments in the provinces of Transvaal, western Natal, Lesotho and eastern Free State, and in the southern coastal mountains of western and eastern Cape Province.
B. caudalis	(Smith, 1849)	0	Horned adder	The arid region of south-west Africa: south-west Angola, Namibia, across the Kalahari Desert of southern Botswana, into northern Transvaal and southwestern Zimbabwe. In South Africa it is found from the northern Cape Province south to the Great Karoo.
B. cornuta	(Daudin, 1803)	1	Many-horned adder	The coastal region of south-west Namibia through west and south-west Cape Province in South Africa. There are also a few isolated populations in eastern Cape Province.
B. gabonica	(Duméril, Bibron & Duméril, 1854)	1	Gaboon viper	Guinea, Ghana, Togo, Nigeria, Cameroon, DR Congo, Central African Republic, southern Sudan, Uganda, Kenya, eastern Tanzania, Zambia, Malawi, eastern Zimbabwe, Mozambique, northeast KwaZulu-Natal Province in South Africa.
B. heraldica	(Bocage, 1889)	0	Angolan adder	The high plateau of central Angola.
B. inornata	(Smith, 1838)	0	Plain mountain adder	Isolated population on the Sneeuberg, eastern Cape Province, South Africa.
B. nasicornis	(Shaw, 1792)	0	Rhinoceros viper	From Guinea to Ghana in West Africa, and in Central Africa in the Central African Republic, southern Sudan, Cameroon, Gabon, Congo, DR Congo, Angola, Rwanda, Uganda and western Kenya.
B. parviocula	Böhme, 1977	0	Ethiopian mountain adder	Known from only three localities in the highlands to south-west Ethiopia, at altitudes of 2000-3000 m.
B. peringueyi	(Boulenger, 1888)	0	Peringuey's desert adder	The Namib Desert from southern Angola to Lüderitz, Namibia.
B. rubida	Branch, 1997	0	Red adder	Several isolated populations in the northern Cape Fold Mountains and inland escarpment in Western Cape Province, South Africa.
B. schneideri	(Boettger, 1886)	0	Namaqua dwarf adder	White coastal sand dunes from Namibia, near Lüderitz, south to Hondeklip Bay, Little Namaqualand, South Africa.
B. worthingtoni	Parker, 1932	0	Kenyan Horned Viper	Restricted to Kenya's high central Rift Valley at altitudes over 1500 m.
B. xeropaga	Haacke, 1975	0	Desert mountain adder	North-western Cape Province in South Africa and the arid mountains of the lower Orange River basin, north into southern Namibia and Great Namaqualand as far as Aus.

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

Taxonomy

Other species may be encountered in literature, such as:

• B. albanica - Hewitt, 1937
• B. armata - Smith, 1826

Lenk et al. (1999) used molecular data (immunological distances and mitochondrial DNA sequences) to estimate the phylogenetic relationships among species of Bitis. They identified four major monophyletic groups for which they created four subgenera:

• Bitis - B. arietans
• Calechidna - B. albanica, B. armata, B. atropos, B. caudalis, B. cornuta, B. heraldica, B. inorata, B. peringueyi, B. rubida, B. schneideri, B. xeropaga
• Macrocerastes - B. gabonica, B. nasicornis, B. parviocula
• Keniabitis - B. worthingtoni

For now, this division is of little consequence as far as the nomenclature is concerned. However, the definition of subgenera within a genus is often the sign of an impending split. Therefore, anyone interested in these snakes would do well to familiarize themselves with these new subgenera.

See also

• Viperinae.
• List of viperine species and subspecies.
• True vipers - Common names.
• True vipers - Synonymy.
• Snake (animal)bite.

Other references

• Branch WR. 1999. Dwarf adders of the Bitis cornuta-inornata complex (Serptentes: Viperidae) in Southern Africa. Kaupia (Darmstadt) (8): 39-63.
• Lenk, P., H.-W. Herrmann, U. Joger, & M. Wink (1999) Phylogeny and taxonomic subdivision of Bitis (Reptilia: Viperidae) based on molecular evidence. Kaupia, 8: 31-38.
• U.S. Navy. 1991. Poisonous Snakes of the World. New York: Dover Books. (Reprint of US Govt. Printing Office, Washington D.C.) 232 pp. ISBN 0-486-26629-X.

External links

• Southern adder (Bitis armata) at ARKive. Accessed 5 October 2006.