Jump to content

Black-necked spitting cobra

This is a good article. Click here for more information.
From Wikipedia, the free encyclopedia

This is an old revision of this page, as edited by RedGKS (talk | contribs) at 16:50, 13 March 2012. The present address (URL) is a permanent link to this revision, which may differ significantly from the current revision.

Black-necked spitting cobra
Naja nigricollis
File:Naja nigricollis Sunset 09 Warren Klein.jpg
Naja nigricollis in a defensive posture
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Order:
Squamata
Family:
Elapidae
Genus:
Naja

Laurenti, 1768
Species:
N. nigricollis
Binomial name
Naja nigricollis
The approximate range of Naja nigricollis in Africa
Synonyms[2]
  • Naja nigricollis atriceps
    Laurent, 1955
  • Naja nigricollis occidentalis
    Laurent, 1973
  • Naja crawshayi
    Broadley & Cotterill, 2004

Naja nigricollis, commonly known as the black-necked spitting cobra, is a species of spitting cobra found mostly in sub-Saharan Africa. They are moderately sized snakes that can grow to a length of 1.2 to 2.2 m (3.9 to 7.2 ft) in length. Their coloration and markings can vary considerably. They prey primarily on small rodents. They possess medically significant venom, although the mortality rate for untreated bites on humans is relatively low (~ 5-10%). Like other spitting cobras, they can eject venom from their fangs when threatened. The venom irritates the skin and can cause permanent blindness if it enters the eyes.

Naja nigricollis belongs to the cobra genus Naja under the family Elapidae. It previously included two subspecies that have been moved to the species Naja nigricincta - the zebra spitting cobra (Naja nigricincta nigricincta) and the black spitting cobra (Naja nigricincta woodi).

Description

N. nigricollis is a moderately sized, venomous snake with a moderately distinct head; the shape of the head is due primarily to two large venom glands found on each side of the head. Its colour can vary depending on region of origin. Some specimens are black or pale grey with a yellow or reddish ventral side with a broad, black neck band, often with an orange or pinkish bar on the neck. Other specimens can be yellowish-brown or have a yellow copper colour and are missing the bandings around the neck and the reddish colour on the belly. Some other specimens are deep reddish-brown, and yet others can be an olive brown.[3] Some can even be striped black and white.[4] There are 21-23 dorsal scales at the mid-body, 182-196 ventral scales, and 54-66 subcaudal scales.[5] This species generally grows to a length of 1.2 metres (3.9 ft) to 2.2 metres (7.2 ft). These sizes are subject to trends based on geographic location and subspecies.

Distribution

The species is very common and is widespread throughout sub-Saharan Africa and is found in western, eastern, central, and southern Africa. It can be found all along eastern Africa south of the Sahara Desert in Kenya, Uganda, Tanzania, Rwanda, and southern Somalia. It is found in Nigeria, Liberia, Senegal, and Benin in western Africa. It is common in Zambia, Central African Republic, Angola, and Cameroon in central Africa. In southern Africa, it is found in South Africa, Swaziland, Botswana, Namibia, Mozambique, and other nations.[3]

Habitat, behavior, and ecology

N. nigricollis usually inhabits savanna and semidesert regions of Africa. However, they can be found at altitudes up to 1,800 metres (5,900 ft), as well as in tropical and subtropical regions of central Africa in moist savanna and cleared former forest regions, particularly near rivers and streams.[6] Adaptable snakes, Naja n. nigricollis occurs in southeastern Nigeria where their habitat has been transformed from rainforest to man-made farmlands, plantations, suburban areas, and a few fragmented forests. This species of cobra has found advantages in the drastic changes which have taken place in Nigeria's rainforests. A study by herpetologist Luca Luiselli, suggests this snake now forages in much drier microhabitats.[7]

The range of Naja nigricollis is currently expanding from the southeastern regions of Nigeria to the more desert and arid conditions in the central part of the nation.[5] They also live in coastal scrubs and dry grasslands. Like other cobra species, they may find abandoned termite mounds or rodent holes to hide or cool off. However, tree trunks seem to be their favourite hiding places. They are excellent tree climbers, thus can be arboreal at times. Because they are so common across Africa, they are encountered in villages or small towns where they may come in direct contact with people.[5]

Unlike other snakes, Naja nigricollis can be either nocturnal or diurnal depending on the time of year, geographic location, and average daytime temperature. This adaptability allows the snake to better regulate its body temperature and to gain access to the most abundant food sources of a particular area. It feeds primarily on small rodents, such as small rats and mice, but will eat lizards, eggs and other snakes.[8]

Like other snakes, it may fall prey to different raptors, especially different species of snake eagles which migrate to Africa when it is winter in the Northern Hemisphere. The short-toed snake eagle (Circaetus gallicus) may be a particular threat, as it is almost strictly an ophiophagus raptor.[9] Other snakes also prey on this species.[10]

Like other spitting cobras, this species is known for its ability to project venom at a potential threat. The venom is an irritant to the skin and eyes. If it enters the eyes, symptoms include extreme burning pain, loss of coordination, partial loss of vision and permanent blindness. N. nigricollis is known for its tendency to liberally spit venom with only the slightest provocation. However, this aggressiveness is counterbalanced by it being less prone to bite than other related species.[6][8]

This species is sometimes found in captivity, and wild-caught individuals are generally nervous and prone to spitting. Captive-bred animals tend to be much more docile and calm when compared to their wild-caught counterparts.[3]

Reproduction

Like other cobra species, this snake is oviparous.[11] The mating season of this species can vary from the end of winter (September) to the beginning of summer (December). Usually, the mating season is the same whether in captivity or in the wild. Females will usually lay 10 to 15 eggs, but they can lay anywhere between eight and 22 eggs at a time.[10] The gestation period lasts about 90–100 days, but once the eggs are laid, they hatch in 60–70 days, and need to be in a temperature of 28-30°C (82.4-86°F). At birth, the young are about 20 to 25 centimeters (7.9 to 9.8 in) in length and are completely independent.

Venom

The venom of Naja nigricollis is somewhat unique among elapids in that it consists primarily of cytotoxins,[12] but with other components also. It retains the typical elapid neurotoxic properties while combining these with highly potent cytotoxins (necrotic agents)[13] and cardiotoxins.[14] Bite symptoms include severe external hemorrhaging and tissue necrosis around the bite area and difficulty breathing. Although mortality rate in untreated cases is low (~ 5-10%),[15] when death occurs it is usually due to asphyxiation by paralysis of the diaphragm. The LD50 of Naja nigricollis is 2 mg/kg SC and 1.15 mg/kg IV. The average venom yield per bite of this species is 200 to 350 mg ( dry weight ) according to Minton (1974).[6][16]

Taxonomy and etymology

Naja nigricollis is classified under the genus Naja of the family Elapidae. It was first described by Norwegian zoologist Johan Reinhardt in 1843. The generic name Naja is a Latinisation of the Sanskrit word nāgá (नाग) meaning "cobra". The specific epithet nigricollis is Latin for "black-necked": niger meaning "black" and collis meaning "neck".[17]

Naja nigricollis previously included two subspecies - Naja nigricollis nigricincta and Naja nigricollis woodi. But genetic studies in 2007 by Wolfgang Wüster et al. have concluded that these subspecies should be treated under a separate species, Naja nigricincta.[18][19]

See also

References

  1. ^ Reinhardt, J (1843). "Naja nigricollis". Beskrivelse ofnogle nye slangearter. p. 37.
  2. ^ "Naja nigricollis REINHARDT, 1843". Reptile Database. http://reptile-database.reptarium.cz. Retrieved 14 February 2012. {{cite web}}: External link in |publisher= (help)
  3. ^ a b c Mastenbroek, Richard. "Black-neck Spitting Cobra" (PDF). DEVENOMIZED. www.devenomized.com. Retrieved 20 December 2011.
  4. ^ "Kraits Cobras Sea Snakes and Relatives: Elapidae - Black-necked Spitting Cobra (naja Nigricollis): Species Accounts". Retrieved 21 December 2011.
  5. ^ a b c Abriol, Sabrina. "Spitting cobra (Naja nigricollis)" (PDF). Herpetology - Dr. Dever. University of San Francisco, California. Retrieved 21 December 2011.
  6. ^ a b c "Naja nigricollis - General Details, Taxonomy and Biology, Venom, Clinical Effects, Treatment, First Aid, Antivenoms". WCH Clinical Toxinology Resource. University of Adelaide. Retrieved 20 December 2011.
  7. ^ Luiselli, Luca (2001). "The ghost of a recent invasion in the reduced feeding rates of spitting cobras during the dry season in a rainforest region of tropical Africa". Acta Oecologica. 22 (5): 311–314. doi:10.1016/S1146-609X(01)01113-4.
  8. ^ a b Spawls, Stephen; Branch, Bill (1995). Dangerous Snakes of Africa. London, UK: Blandford Press. p. 91. ISBN 0713723947.
  9. ^ Bauchot, Roland (2006). Snakes: A Natural History. New York, USA: Sterling; illustrated edition edition. p. 176. ISBN 1402731817.
  10. ^ a b FitzSimons, Vivian FM (1970). A field guide to the snakes of Southern Africa. Canada: HarperCollins. ISBN 0002121468.
  11. ^ Engelmann, Wolf-Eberhard (1981). Snakes: Biology, Behavior, and Relationship to Man. Leipzig; English version NY, USA: Leipzig Publishing; English version published by Exeter Books (1982). p. 71. ISBN 0-89673-110-3.
  12. ^ Marais, Johan (2004). A Complete Guide to the Snakes of Southern Africa. Cape Town, South Africa: Struik Nature. ISBN 186872932X.
  13. ^ Chaim-Matyas, Adina (20). "Cytotoxic activity of various snake venoms on melanoma, B16F10 and chondrosarcoma". Life Sciences. 40 (16): 1601–1607. doi:10.1016/0024-3205(87)90126-3. PMID 3561167. {{cite journal}}: Check date values in: |date= and |year= / |date= mismatch (help); Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  14. ^ Fryklund, Linda (1975). "Complete covalent structure of a cardiotoxin from the venom of Naja nigricollis (African black-necked spitting cobra)". Biochemistry. 14 (13): 2865–2871. doi:10.1021/bi00684a012. PMID 1148181. Retrieved 22 December 2011. {{cite journal}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |month= ignored (help)
  15. ^ Warrell, David A. "Snake bite" (PDF). Seminar. Lancet 2010 (volume 375, issue 1). Retrieved 20 December 2011.
  16. ^ Thomas, Sean. "LD50 for various snakes". Australian Venom and Toxin database. www.seanthomas.com. Retrieved 20 December 2011.
  17. ^ Reinhardt, J (1847). "Herpetology". Reports on zoology for 1843, 1844. Ray Society. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help); Unknown parameter |editors= ignored (|editor= suggested) (help)
  18. ^ Wüster, W., S. Crookes, I. Ineich, Y. Mane, C.E. Pook, J.-F. Trape & D.G.Broadley (2007) "The phylogeny of cobras inferred from mitochondrial DNA sequences: evolution of venom spitting and the phylogeography of the African spitting cobras (Serpentes: Elapidae: Naja nigricollis complex)". Molecular Phylogenetics and Evolution, 45: 437-453.
  19. ^ Naja nigricincta at the Reptarium.cz Reptile Database. Accessed 29 December 2008.
Wikispecies has information related to Naja nigricollis.
Retrieved from "https://en.wikipedia.org/enwiki/w/index.php?title=Black-necked_spitting_cobra&oldid=481706000"