King Cobra

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 is widespread throughout Southeast Asia and parts of India, and is found mostly in forested areas. The king cobra is fierce, agile, and can deliver a large quantity of highly potent venom in a single bite. It is one of the most dangerous and feared Asiatic snakes.^[2]

Contents 1 Profile 2 Characteristics 2.1 Identification 2.2 Scalation 3 Habitat 4 Behavior 4.1 Defense 5 Diet 6 Venom 7 Reproduction 8 Other culture 9 Related species 10 Gallery 11 References

Profile

The king cobra is a large and powerful snake, averaging 3.6–4 m (12–13 feet) in length and typically weighing about 6 kg (13.2 lb). A particularly large specimen was kept captive at the London Zoo, and grew to 5.7 m (18.8 ft) before being euthanized upon the outbreak of World War II.^[3] Despite their large size, king cobras are fast and agile.

Characteristics

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 king cobra is about 20 years.

Identification

The king cobra is the sole member of genus Ophiophagus, while most other cobras are members of the genus Naja. They can be identified from other cobras by size and hood marks. King cobras are 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 cobras. A fullproof method of identification if the head is 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.^[2]

Habitat

The king cobra is distributed across South and Southeast Asia, but is not common. It lives in dense highland forests,^[1][4], preferring areas dotted with lakes and streams. King cobra populations have dropped in some areas of its range because of the destruction of forests, but despite this, the snake is not listed by the IUCN as in danger of becoming extinct. It is, however, listed as an Appendix II Animal within CITES.^[5]

Behavior

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^[6] and sensitivity to earth-borne vibration to track its prey.^[7] Following envenomation, the king cobra will begin to swallow its struggling prey while its toxins begin the digestion of its victim.^[1] King cobras, like all snakes, have flexible jaws. The jaw bones are connected by pliable ligaments, enabling the lower jaw bones to move independently. ^[1] Like all snakes, the king cobra swallows 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][8]

Defense

The king cobra is a fierce and highly aggressive snake.^[9] When threatened, it raises up the anterior portion of its body, flattening the neck, showing the fangs and hissing loudly. It is easily irritated by closely approaching objects or sudden movements. The king cobra attacks quickly, and the strike distance is about 7 feet; people can easily misjudge the safe distance. The king cobra may deliver multiple bites in a single attack, or bite and hold on.^[10] Although it is undoubtedly a very dangerous snake, it prefers to escape unless it is cornered or provoked. ^[9]

If a king cobra encounters a natural predator, such as the mongoose, which has some resistance to the neurotoxins,^[11] 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.

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.^[12]

Diet

King cobra's genus name, Ophiophagus, literally means "snake-eater", and its diet consists primarily of other snakes, including rat snakes, sizeable pythons and even other venomous snakes (including kraits, cobras and smaller members of its own species).^[8][13] 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, like birds and larger rodents, using its muscular body, though this is uncommon.^[1][13] 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; this leads them near human settlements.

Venom

The venom of the King Cobra is primarily neurotoxic, but also contains cardiotoxic compounds.^[8] It is composed mostly of proteins and polypeptides. During a bite, venom is forced through the snake's half-inch (1.25 cm) fangs and into the wound, and quickly attacks the victim's central nervous system, and induces severe pain, blurred vision, vertigo, drowsiness, and paralysis.^[14] Envenomation progresses to cardiovascular collapse, and the victim falls into a coma. Death soon follows due to respiratory failure.

In the past, the LD50 of its venom was treated as 1.6 mg/kg-1.8 mg/kg (which is one of the least toxic elapids). However, a recent toxicology study shows that the LD50 of Chinese King Cobra venom is 0.34 mg/kg.^[15] This proves the King Cobra can actually be more venomous than most of the other species with its range, like the Chinese Cobra.^[16] The King Cobra is also capable of delivering larger quantities of venom than most other venomous snakes, injecting a 380-600 mg dose in a single bite. This quantity is enough to kill 20-40 grown men or even an adult elephant. One bite can cause the death of a healthy adult human within 15 minutes,^[15] but death usually occurs between 30-45 minutes.^[14][16][17] The mortality rate from a bite can be over 75%,^[8][18] or only 33%, depending upon treatment details. It is regarded as one of the deadliest snakes in the world.^[16][19]

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.^[20] Ohanin, a protein component of the venom, causes hypolocomotion and hyperalgesia in mammals.^[21] Other components have cardiotoxic,^[22] cytotoxic and neurotoxic effects.^[23]

Reproduction

The female king cobra is a very dedicated parent. Before she is ready to lay her eggs, she uses the coils of her long body to gather a big mound of leaf litter. She deposits 20–40 eggs into the mound, which acts as an incubator. The female stays with her eggs and guards the mound tenaciously, rearing up into a threat display if any large animal gets too close.^[24]

Inside the mound the female has built, the eggs are incubated at a steady 28 °C (82 °F). When the eggs start to hatch, instinct causes her to leave the nest and find prey to eat so she does not eat her young.^[25] The baby king cobras can have a length of 45 to 55 centimeters (18 to 22 in). They are highly aggressive and have already developed potent venom, which is as deadly as that of an adult.

Other culture

In Burma, king cobras are often used by female snake charmers.^[13] 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.^[13] The charmer kisses the snake on the top of its head at the end of the show.^[13]

Related species

The king cobra belongs to the family Elapidae. There are over 200 species of elapids found around the world, except Antarctica and Europe. All are venomous and have short, fixed fangs (proteroglyphs), but may differ widely in habits, behaviour and appearance. Some other well-known species of the Elapidae are the coral snake, the death adder and the black mamba.

Gallery

King cobra in St. Louis Zoo

King cobra found in forest

South Indian king cobra

Adult male king cobra

References