King Cobra

King Cobra
This article is about the snake. For other uses, see King Cobra (disambiguation).

Unikonta

King Cobra
Conservation status
Scientific classification e
Kingdom: Animalia
Phylum: Chordata
Class: Reptilia
Order: Squamata
Suborder: Serpentes
Family: Elapidae
Genus: Ophiophagus
Species: O. hannah
Binomial name
Ophiophagus hannah
Cantor, 1836
  Distribution of the king cobra
Synonyms

Genus-level:

The king cobra (Ophiophagus hannah) is the world's longest venomous snake, with a length up to 5.6 m (18.5 ft).[1] This species, which preys chiefly on other snakes, is found predominantly in forests from India through Southeast Asia to the Philippines and Indonesia. Despite the word "cobra" in its name, this snake is not a member of Naja ("true cobras") but belongs to its own genus.

Contents

Profile

The king cobra is a large and powerful snake, averaging 3 to 4 meters (9.8 to 13 ft) in length and typically weighing about 6 kilograms (13 lb). The longest known specimen was kept captive at the London Zoo, and grew to around 18.5 to 18.8 feet (5.6 to 5.7 m) before being euthanized upon the outbreak of World War II. The heaviest wild specimen was caught at Royal Island Club in Singapore in 1951 which weighed 12 kilograms (26 lb) and measured 4.8 meters (16 ft), though an even heavier captive specimen was kept at New York Zoological Park and was measured as 12.7 kilograms (28 lb) at 4.4 meters (14 ft) long in 1972, recently found a 12ft king Cobra in Tripura(India).[2] The length and mass of the snakes highly depend on their localities and some other factors. Despite their large size, typical king cobras are fast and agile.[3]

Characteristics

King cobra skull, lateral view, showing fangs

The skin of this snake is either olive-green, tan, or black, and it has faint, pale yellow cross bands down the length of the body. The belly is cream or pale yellow, and the scales are smooth. Juveniles are shiny black with narrow yellow bands (can be mistaken for a banded krait, but readily identified with its expanded hood). The head of a mature snake can be quite massive and bulky in appearance, though like all snakes, they can expand their jaws to swallow large prey items. It has proteroglyph dentition, meaning it has two short, fixed fangs in the front of the mouth which channel venom into the prey like hypodermic needles. The male is larger and thicker than the female. The average lifespan of a wild king cobra is about 20 years.[4]

Identification

The king cobra is the sole member of genus Ophiophagus, while most other cobras are members of the genus Naja. They can be distinguished from other cobras by size and hood marks. King cobras are generally larger than other cobras, and the stripe on the neck is like the symbol "^" instead of a double or single eye(s) shape that may be seen in most of the other Asian cobras. A foolproof method of identification is if on the head, clearly visible, is the presence of a pair of large scales known as occipitals, at the back of the top of the head. These are behind the usual "nine-plate" arrangement typical of colubrids and elapids, and are unique to the king cobra.

Scalation

Dorsal scales: midbody 15 rows; Ventral scales: Males 235-250, females 239-265; Tail: Subcaudal scales single or paired in each row, 83-96 in males and 77-98 in females.[3]

Habitat

The king cobra is distributed across South Asia, Southeast Asia, and the southern areas of East Asia (southern China) where it is not common. It lives in dense highland forests,[1][5] preferring areas dotted with lakes and streams. King cobra populations have dropped in some areas of its range because of the destruction of forests. It is listed as an Appendix II Animal within CITES.[6]

Scalation of the King Cobra

Behaviour

King cobras, like other snakes, receive chemical information ("smell") via their forked tongues, which pick up scent particles and transfer them to a special sensory receptor (Jacobson's organ) located in the roof of its mouth.[1] When the scent of a meal is detected, the snake flicks its tongue to gauge the prey's location (the twin forks of the tongue acting in stereo); it also uses its keen eyesight (king cobras are able to detect moving prey almost 100 m [300 feet] away), intelligence[7] and sensitivity to earth-borne vibration to track its prey.

Another theory, not yet proven beyond doubt, is that the king cobra has a very sharp memory. According to a myth, the picture of the killer of a king cobra stays in the eyes of the snake, which is later picked up by the partner and is used to hunt down the killer for revenge. To prove this theory, a king cobra was captured and left free in an enclosure which had small openings. Numerous people stood in front of the openings but the snake rose to its full height and locked eyes only with the captor. Due to this myth, whenever a cobra is killed, specially in India, the head is either crushed or burned in order to damage the eyes completely.[8] Following envenomation, the king cobra will begin to swallow its struggling prey while its toxins begin the digestion of its victim. King cobras, like all snakes, have flexible jaws. The jaw bones are connected by pliable ligaments, enabling the lower jaw bones to move independently, enabling the King cobra to swallow its prey whole. The expansion of the jaw enables the snake to swallow prey much larger than its head.[1]

King cobras are able to hunt at all times of day, although it is rarely seen at night, leading most herpetologists to classify it as a diurnal species.[1][9]

Defense

When confronted this species will quickly attempt to escape and avoid any sort of confrontation.[10] However, if cornered, the king cobra can be very aggressive if provoked.[4][11] When threatened, it rears up the anterior portion of its body when extending the neck, showing the fangs and hissing loudly.[4][12] It can be easily irritated by closely approaching objects or sudden movements. When raising its body, the king cobra can still move forward to strike and the attack range can be as far as 2 meters where people can easily misjudge the safe zone.[4] The king cobra may deliver multiple bites in a single attack but adults are known to bite and hold on.[13] In spite of being a highly dangerous snake, it prefers to escape first unless there is no way to go.[11] Since this species is secretive and tends to inhabit less-populated forested regions and dense jungle,[4] it is rarely encountered.

If a king cobra encounters a natural predator, such as the mongoose, which has resistance to the neurotoxins,[14] the snake generally tries to flee. If unable to do so, it forms the distinctive cobra hood and emits a hiss, sometimes with feigned closed-mouth strikes. These efforts usually prove to be very effective, especially since it is more dangerous than other mongoose prey, as well as being much too large for the small mammal to kill with ease.

Diet

The king cobra's genus name, Ophiophagus, means "snake-eater", and its diet consists primarily of other snakes, including ratsnakes, small pythons and even other venomous snakes (smaller members of its own species, true cobras (of the genus Naja), and even the much more venomous members of the krait family.[9][15] When food is scarce, they may also feed on other small vertebrates, such as lizards, birds, and rodents. In some cases, the cobra may "constrict" its prey, such as birds and larger rodents, using its muscular body, though this is uncommon.[1][15] After a large meal, the snake may live for many months without another one because of its slow metabolic rate.[1] The king cobra's most common meal is the ratsnake; pursuit of this species often brings king cobras close to human settlements.

Venom

The venom of the king cobra consists primarily of neurotoxins, but it also contains cardiotoxic and some other compounds.[9] Toxic constituents are mainly proteins and polypeptides.[16]

During a bite, venom is forced through the snake's 1.25 to 1.5 centimeters (0.49 to 0.59 in) fangs into the wound, and the toxins begin to attack the victim's central nervous system. Symptoms may include severe pain, blurred vision, vertigo, drowsiness, and paralysis. Envenomation progresses to cardiovascular collapse, and the victim falls into a coma. Death soon follows due to respiratory failure. Moreover, king cobra envenomation is clinically known to cause renal failure.[17]

A 1990 book makes a passing statement of a LD50 of 0.34 mg/kg for this species[18], however this value is inconsistent with most toxicological studies.[19][20][21] For example, a recent study lists the LD50 of the king cobra venom as 1.6 mg/kg – 1.8 mg/kg[21], making it's venom one of the least potent among the elapids. This value is further backed up by another toxicological study which lists the LD50 of the king cobra at 1.7 mg/kg.[20] A similar mean LD50 value of 1.93 mg/kg was obtained from the venom of five wild caught king cobras in Southeast Asia (Meier et al 1995).[22]

This species is capable of delivering a large quantity of venom, injecting a dose anywhere from 200-500 milligrams on average[12][18][23] and can up to 7ml.[4] Though the venom is weak compared to most other elapids based upon the LD50 in mice,[17] it can still deliver a bite which can potentially kill a human due to the massive amount of venom it delivers in a single bite. Mortality can vary sharply with amount of venom involved, most bites involve nonfatal amounts.[24] According to a research report from the University of Adelaide Department of Toxinology, an untreated bite has a mortality rate of 50-60%[25] Depending on many factors, death can occur as early as 30 minutes after being bitten by this species but this is exceptionally rare as most untreated bite victims in Asia live through bites.[17][24]

There are two types of antivenom made specifically to treat king cobra envenomations. The Red Cross in Thailand manufactures one, and the Central Research Institute in India manufactures the other; however, both are made in small quantities and are not widely available.[26] Ohanin, a protein component of the venom, causes hypolocomotion and hyperalgesia in mammals.[27] Other components have cardiotoxic,[28] cytotoxic and neurotoxic effects.[29] In Thailand, a concoction of alcohol and the ground root of turmeric is ingested, which has been clinically shown to create a strong resilience against the venom of the king cobra, and other snakes with neurotoxic venom.[30]

The haditoxin in the king cobra venom was discovered by Singaporean scientists to be structurally unique and can have unique pharmacological properties.[31] Biochemical studies confirmed that it existed as a non-covalent dimer species in solution. Its structural similarity to short-chain α-neurotoxins and κ-neurotoxins notwithstanding, haditoxin exhibited unique blockade of α7-nAChRs (IC50 180 nM), which is recognized by neither short-chain α-neurotoxins nor κ-neurotoxins.[16]

Reproduction

The king cobra is unusual among snakes in that the female king cobra is a very dedicated parent. She makes a nest for her eggs, scraping up leaves and other debris into a mound in which to deposit them, and remains in the nest until the young hatch.

A female usually deposits 20 to 40 eggs into the mound, which acts as an incubator. She stays with the eggs and guards the mound tenaciously, rearing up into a threat display if any large animal gets too close,[32] for roughly 60 to 90 days.

Inside the mound the eggs are incubated at a steady 28 °C (82 °F). When the eggs start to hatch, instinct causes the female to leave the nest and find prey to eat so she does not eat her young.[33] The baby king cobras, with an average length of 45 to 55 centimeters (18 to 22 in), have venom which is as potent as that of the adults. They may be brightly marked but these colours often fade as they mature. They are alert and nervous, being highly aggressive if disturbed.[12]

Other information

Other culture

In Burma, king cobras are often used by female snake charmers.[15] The charmer is usually tattooed with three pictograms, using an ink mixed with snake venom; superstition holds that it protects the charmer from the snake.[15] The charmer kisses the snake on the top of its head at the end of the show.[15]

Hiss

Bioacoustic analysis of the "growl" of the king cobra has shown that it differs significantly from other snakes. Generally a typical snake hiss has a broad-frequency span [~3,000 to 13,000 Hz] with a dominant frequency near 7,500 Hz, whereas the "growl" of the king cobra consists of frequencies below 2,500 Hz, with a dominant frequency near 600 Hz.[34]

Related species

The king cobra belongs to the family Elapidae which includes other well known snakes, such as the various species of cobra (ie. Cape cobra, Indian cobra, etc), the coral snake, the death adder, kraits, mambas, and taipans.

Gallery

  • King cobra in St. Louis Zoo

  • A juvenile found in forest

  • Indian king cobra

  • A male king cobra extending its hood.

References

  1. ^ a b c d e f g Mehrtens, John (1987). Living Snakes of the World. New York: Sterling. ISBN 0806964618. 
  2. ^ Wood, The Guinness Book of Animal Facts and Feats. Sterling Pub Co Inc (1983), ISBN 978-0851122359
  3. ^ a b Venomous Land Snakes, Dr.Willott. Cosmos Books Ltd. ISBN 9882113265. 
  4. ^ a b c d e f "National geographic- KING COBRA". http://animals.nationalgeographic.com/animals/reptiles/king-cobra/. "They are fiercely aggressive when cornered (line 28-29);average life span in the wild: 20 years (fast facts)" 
  5. ^ Miller, Harry (September 1970). "The Cobra, India's 'Good Snake'". National Geographic 20: 393–409 
  6. ^ "CITES List of animal species used in traditional medicine". http://www.cites.org/eng/com/aC/17/E17i-05Rev.doc. Retrieved 2007-09-01. 
  7. ^ Philadelphia Zoo - King cobra
  8. ^ Taylor, David (1997). King Cobra.. National Geographic Magazine. Archived from the original on 2007-08-20. http://web.archive.org/web/20070820143553/http://www.nationalgeographic.com/kingcobra/index-n.html. Retrieved 2007-09-08 
  9. ^ a b c Capula, Massimo; Behler (1989). Simon & Schuster's Guide to Reptiles and Amphibians of the World. New York: Simon & Schuster. ISBN 0671690981. 
  10. ^ Reptile Knowledge (King cobra)
  11. ^ a b "Ophiophagus hannah". http://animaldiversity.ummz.umich.edu/site/accounts/information/Ophiophagus_hannah.html. 
  12. ^ a b c Mark O'Shea. Venomou snakes of the world. ISBN 9780691150239. "Average venom yield is 200-500 mg" 
  13. ^ "King Cobra". http://drdavidson.ucsd.edu/Portals/0/snake/Ophiopha.htm. 
  14. ^ Dr. Zoltan Takacs. "Why the cobra is resistant to its own venom". http://zoltantakacs.com/zt/sc/Naja.shtml. Retrieved 2007-09-05. 
  15. ^ a b c d e Coborn, John (October 1991). The Atlas of Snakes of the World. TFH Publications. pp. 30, 452. ISBN 978-0866227490. 
  16. ^ a b "Structural and Functional Characterization of a Novel Homodimeric Three-finger Neurotoxin from the Venom of Ophiophagus hannah (King Cobra)". http://www.jbc.org/content/285/11/8302.abstract. 
  17. ^ a b c Davidson, Terence. "IMMEDIATE FIRST AID". University of California, San Diego. http://drdavidson.ucsd.edu/Portals/0/snake/Ophiopha.htm. Retrieved 2011-09-24. 
  18. ^ a b Snake of medical importance. Singapore: Venom and toxins research group. ISBN 9971622173. http://i55.tinypic.com/21jvc7p.jpg. 
  19. ^ Handbook of clinical toxicology of animal venoms and poisons. 236. USA: CRC Press. 1995. pp. 768. ISBN 0849344891. 
  20. ^ a b LD50 for King Cobra
  21. ^ a b "LD50 Menu". http://www.kingsnake.com/toxinology/LD50/LD50men.html. Retrieved 2010-04-21. 
  22. ^ Handbook of clinical toxicology of animal venoms and poisons. 236. USA: CRC Press. 1995. pp. 768. ISBN 0849344891. 
  23. ^ "science-the king cobra". http://www.nytimes.com/2010/10/26/science/26creatures.html. 
  24. ^ a b Mortality Rate
  25. ^ "University of Adelaide Clinical Toxinology Resources". http://www.toxinology.com/fusebox.cfm?fuseaction=main.snakes.display&id=SN0048. 
  26. ^ "Munich AntiVenom Index:Ophiophagus hannah". Munich Poison Center. MAVIN (Munich AntiVenom Index). 01/02/2007. http://www.toxinfo.org/antivenoms/indication/OPHIOPHAGUS_HANNAH.html. Retrieved 2007-09-02. 
  27. ^ Pung, Y.F., Kumar, S.V., Rajagopalan, N., Fry, B.G., Kumar, P.P., Kini, R.M. 2006 Ohanin, a novel protein from king cobra venom: Its cDNA and genomic organization. Gene 371 (2):246–256
  28. ^ Rajagopalan, N., Pung, Y.F., Zhu, Y.Z., Wong, P.T.H., Kumar, P.P., Kini, R.M. 2007 β-Cardiotoxin: A new three-finger toxin from Ophiophagus hannah (King Cobra) venom with beta-blocker activity. FASEB Journal 21 (13):3685–3695
  29. ^ Chang, L.-S., Liou, J.-C., Lin, S.-R., Huang, H.-B. 2002Purification and characterization of a neurotoxin from the venom of Ophiophagus hannah (king cobra). Biochemical and Biophysical Research Communications 294 (3):574–578
  30. ^ Ernst, Carl H. & Evelyn M. (2011). Venomous Reptiles of the United States, Canada, and Northern Mexico: Heloderma, Micruroides, Micrurus, Pelamis, Agkistrodon, Sistrurus. JHU Press. pp. 44–45. ISBN 9780801898754. http://books.google.com/books?id=o8DTAQffi4UC&pg=PA44. 
  31. ^ "King Cobra venom may lead to a new drug". http://www.upi.com/Science_News/2010/03/10/King-Cobra-venom-may-lead-to-a-new-drug/UPI-22601268231503/. 
  32. ^ Extraordinary Animals: An Encyclopedia of Curious and Unusual Animals. Westport, Conn.Greenwood Press. ISBN 9780313339226.
  33. ^ National Geographic Program 17 May 2009
  34. ^ Young, Bruce A. (1991). "Morphological basis of "growling" in the king cobra, Ophiophagus Hannah". Journal of Experimental Zoology 260 (3): 275–287. doi:10.1002/jez.1402600302. PMID 1744612. 


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