King Cobra

The king cobra lives in South and Southeast Asia. In India it is found in the Western Ghats, the eastern and northeastern hills, the foothills of the Himalaya and the Andaman Islands, and it also lives in the Terai of Nepal, southern Bhutan and Bangladesh, in the Sundarbans and the Chittagong hills. From there its range covers Myanmar, Thailand, Laos, Cambodia and Vietnam, southern China and Hainan, the Malay Peninsula, Borneo, Sumatra, Java, Bali and Sulawesi, and the Philippines. It prefers dense forest near streams and rivers, from lowland rainforest and bamboo thickets to mangroves, but it also lives in plantations, rice paddies and the edges of villages, often because rat snakes, its favorite prey, abound there. It has been recorded above 2,000 meters. The village of Agumbe, in the Western Ghats of Karnataka, is known as the capital of the king cobra, and its research station has radio tracked these snakes for years.

The king cobra is the longest venomous snake in the world. Most adults measure three to four meters and weigh six to nine kilograms, and unusually for snakes, males are larger than females. The longest one on record was caught near Port Dickson, in Malaysia, in 1937 and grew to 5.71 meters at the London Zoo, and the heaviest wild one, caught in Singapore in 1951, weighed about 12 kilograms. Its body is slender and smooth, and its head has large scales on top, with a pair of big scales on the back of the head that other cobras lack. Its hood is longer and narrower than that of the Indian cobra. Color changes a lot from region to region: in the north and in India adults are olive or dark brown with pale crossbands, while in the Malay Peninsula and Borneo they are often plain brown or olive with little pattern. Young king cobras are black with bright yellow or white bands, which fade with age.

For almost two centuries the king cobra was considered a single species, but in 2024 a team led by the Indian biologist Gowri Shankar published a study, based on genetics and on scale counts and band patterns, showing that there are four. The northern king cobra (Ophiophagus hannah) keeps the old name and lives from northern and eastern India, the Andamans and Nepal through Myanmar, Indochina and Thailand to southern China. The Sunda king cobra (Ophiophagus bungarus) lives in the Malay Peninsula, Borneo, Sumatra, Java and the southern and central Philippines. The Western Ghats king cobra (Ophiophagus kaalinga) lives only in the mountains of southwestern India, and the Luzon king cobra (Ophiophagus salvatana) only on Luzon, in the Philippines. The split matters for conservation, because each species has a much smaller range than the old single king cobra, and for medicine, since venom can vary between them. The IUCN still treats the king cobra as one species.

The king cobra feeds almost entirely on other snakes, and its scientific name, Ophiophagus, means snake eater. Its favorite prey are rat snakes, which are common around fields and villages, but it also eats kraits, keelbacks, pythons, pit vipers, cobras and even other king cobras, which makes it one of the few cannibals among snakes. When snakes are scarce it occasionally takes monitor lizards. It is an active hunter that searches for prey by flicking its tongue to pick up scent trails, often during the day, and it can follow a snake into burrows and up into trees. It bites, holds on and injects venom that paralyzes the prey within minutes, and then swallows it whole, head first, even when the prey is almost as long as itself. After a big meal a king cobra can go weeks or even months without eating, which helps females survive the long period when they guard their nest.

The king cobra is not the most venomous snake in the world drop by drop: the inland taipan, several sea snakes and many cobras and kraits have more toxic venom. What makes it dangerous is the quantity. A large king cobra can inject several milliliters of venom in a single bite, enough to kill a person within hours, and the often repeated claim that one bite can kill an elephant comes from that huge dose. The venom acts mainly on the nervous system, causing paralysis that ends in respiratory failure. Even so, few people die from king cobra bites: the snake is relatively rare, shy and usually warns before biting, and most of the snakebite deaths in Asia are caused by other species, such as Russell's viper, the Indian cobra, kraits and saw scaled vipers. Treatment needs a specific antivenom, produced in Thailand and other countries, because the common polyvalent antivenom used in India does not cover the king cobra.

The king cobra is mostly active by day and solitary outside the breeding season. It is an active hunter that roams large home ranges, several square kilometers in radio tracked snakes, rather than waiting in ambush. When cornered or provoked, it performs one of the most dramatic threat displays among reptiles: it raises the front third of its body off the ground, high enough to look an adult in the eye, spreads its narrow hood, keeps its eyes fixed on the threat and produces a deep growl rather than the usual hiss, a sound made by special pouches in its windpipe. It can even move forward while standing raised. Despite its size and reputation, the king cobra prefers to retreat when it has the option, and most bites happen when someone tries to catch or kill it. In the breeding season males fight ritual battles, wrestling with their bodies raised to push each other down, without biting.

The king cobra is the only snake known to build a nest. Before laying, the female gathers dead leaves and plant debris with her body, coiling around them to pile them into a mound, often at the base of a tree or bamboo clump. She lays about 20 to 40 eggs inside, and the decomposing leaves keep them warm and humid. Then she rests on top of the nest or close to it and defends it fiercely for most of the two to three months of incubation, which is when females are most likely to be aggressive toward people who come too close. The female usually leaves the nest shortly before the eggs hatch. The young are born fully venomous, measure about 40 to 55 centimeters and are black with bright bands. They are independent from the start and must avoid many predators, including birds of prey, mongooses and other snakes.

The king cobra is listed as Vulnerable on the IUCN Red List since 2010, after assessments showed declines across much of its range, and it is included in Appendix II of CITES, which regulates its international trade. The main threats are the loss of forest to logging, plantations such as oil palm and rubber, and farming; hunting for its skin, meat and use in traditional medicine, especially in China, Vietnam and Laos; and capture for the live animal trade. Many king cobras are also killed by people who find them near their homes. The species is legally protected in India and many other countries, though enforcement varies. Rescue and relocation programs, like those of Agumbe in India and of snake rescuers in Thailand, help reduce conflict. The 2024 split into four species makes conservation even more urgent, because the Luzon and Western Ghats king cobras each live in a single, small region.