king cobra (Ophiophagus hannah) is the world's longest venomous snake, with a length up to 5.6 m (18.5 ft). This species is widespread throughout Southeast Asia and parts of India, and is found mostly in forested areas. 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. 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 and sensitivity to earth-borne vibration to track its prey. Following envenomation, the king cobra will begin to swallow its struggling prey while its toxins begin the digestion of its victim.
When threatened, it raises up the anterior portion of its body, flattening the neck, showing the fangs and hissing loudly. (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.) It is easily irritated by closely approaching objects or sudden movements. The king cobra attacks quickly, and the strike distance is about 2 m (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. 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.
the king cobra's venom was treated as 1.6 mg/kg – 1.8 mg/kg (which was one of the least venomous elapids). However, in recent toxicology study the LD50 of Chinese king cobra venom was found to be 0.34 mg/kg . The value is lower than that of many Naja species found in the same habitats (such as the Chinese cobra), showing that the king cobra can actually be more venomous than many other cobras. The king cobra is also capable of delivering larger quantities of venom than most other snakes, injecting a 380-600 mg dose in a single bite on average. It was reported that a single bite from this species can kill an adult Asian elephant. king cobra is unique 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.
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.