Cobra (snake) - biology. I INTRODUCTION Cobra (snake), name for a group of venomous snakes known for their hooded threat display and dangerous bites. Cobras are found in Africa and Asia, and they have held a special place in human culture from ancient Egypt to modern India. About 30 species of snakes are commonly called cobras, including the king cobra (the world's largest poisonous snake) and varieties that can "spit" venom. The name cobra comes from a Portuguese word for "snake" (short for cobra de capello "snake with a hood"). Cobras belong to the same snake family (Elapidae) as coral snakes and mambas. Not all types of snakes popularly called cobras may be directly related to the same ancestors. Rearing up to display a flattened neck that forms a hood and spraying venom are abilities that apparently evolved more than once in different members of the elapid family of snakes. II HABITAT AND RANGE The different species of cobra live in habitats ranging from tropical rain forests and swamps to savannas and deserts. Because many cobra species prey on small rodents, the snakes may hunt or live in areas around human settlements or in fields where crops grow--both places where rodents thrive. Cobras are found in most parts of Africa except for the Sahara Desert. Their range extends through the Middle East, Central Asia, South Asia and into Southeast Asia as far as Indonesia and the Philippines, and into southern China. III PHYSICAL DESCRIPTION AND BEHAVIOR The famous hood of a cobra is created by elongated ribs that extend the loose skin of the neck behind the snake's head. Cobras raise up the front part of their bodies and flatten their necks to display the hood when they feel threatened or disturbed, often hissing loudly to add a further warning. The neck ribs can be folded back when the snake moves along the ground. Like most snakes, cobras use their forked tongues to detect smells or taste objects. The flicking tongue picks up molecules in the air or along the ground. The tongue then passes over a special organ inside the mouth called Jacobson's organ. Although cobras are not sensitive to air-borne sounds, they can detect sounds through the ground. Bones in their jaws carry vibrations to the ear. Most species have relatively poor eyesight and hunt at dusk or at night. An exception is the king cobra, which is active in the daytime and can see objects over 100 m (330 ft) away. Male cobras are typically larger than females. All cobras lay eggs except for ringhals, which give birth to live young. The females of some species guard their eggs but only female king cobras build nests. IV TYPES OF COBRAS Species of cobra differ from each other in size, habits, and range. The term "true cobra" is used for species that belong to the genus Naja, notable for proportionately larger hoods with an eye-pattern on the back. Species range from 1 and 1.5 m (40 and 60 in) to 3 m (10 ft) long. True cobras are found in much of Africa, Asia, and parts of the Middle East. Water cobras are found in Central Africa and grow to 1.8 to 2 m (6 to 7 ft) in length. Burrowing cobras, also called many-banded snakes, live in parts of the Congo region and in Cameroon, and grow to 60 cm (2 ft). Tree cobras are found in tropical forests in central and west Africa and average 2 to 2.7 m (7 to 9 ft) in length. The king cobra, also known as the hamadryad, is the longest of all poisonous snakes, averaging 3.6 m (12 ft) but sometimes reaching 5.4 m (18 ft) in length. It is found in southern regions of Asia, including India, China, Vietnam, Malaysia, Indonesia, and the Philippines. Desert black cobras live in deserts in the Middle East, and can reach 1.3 m (4 ft) in length. Shieldnose cobras, also called African coral snakes, are 60 to 76 cm (2 to 2.5 ft) long, and occur in dry, sandy areas in southern Africa. Ringhals (also spelled rinkhals) are found in southern Africa and average about 1 m (40 in) in length, sometimes reaching 1.5 m (5 ft). V COBRA BITES AND VENOM Like other members of the elapid family, cobras have fixed fangs in the front of the mouth. The fangs are hollow with an open groove at the bottom. Broken or lost fangs will regrow. The venom-injecting fangs are relatively small compared to the fangs of pit vipers such as rattlesnakes and do not fold back. The lower jaw has special grooves for the tips of the fangs. The opening in the hollow fang tip points forward in cobras that "spit" venom. Cobra venom contains a complex mix of toxins in the form of proteins and polypeptides. The main components are neurotoxins that affect the nervous system of other animals, stopping the heartbeat and breathing. The compounds can also block communication between nerves and muscles. Some toxins mainly affect the heart, causing irregular heartbeats and drops in blood pressure. Other toxins may cause tissue damage and pain. Tens of thousands of people in Africa and in Asia are estimated to die from the bites of different cobra species every year. Farmers and plantation workers in rural parts of Asia are the most common victims. A venomous life-threatening bite may not produce symptoms immediately and observation of a bite victim is recommended for 24 hours. Antivenins (also called antivenoms) exist against the venom of most cobra species. These drugs are produced by "milking" captive or captured snakes for venom then injecting the venom into animals such as horses. The proteins the animals produce against the venom are collected, purified, and injected into human snakebite victims. With adequate medical treatment, a significant number of people recover from cobra bites without antivenin, however. Spraying (or "spitting") venom is a defense found in a number of species of true cobras and in ringhals. Experiments show that the snakes deliberately aim for the eyes in humans and animals. Being struck by sprayed venom is not life-threatening. However, if the venom enters the eyes, it causes instant pain and can damage the mucus membranes and cornea, sometimes resulting in blindness. VI HUNTING AND DIET Most cobras prey on small rodents or other small mammals. They also eat birds, snakes, lizards, frogs, toads, insects, and even eggs. Water cobras catch fish and king cobras specialize in eating other snakes. Similar to other venomous snakes, cobras use venom to subdue their prey before swallowing it whole, generally head first. The venom may contain substances that also break down the prey for digestion. Despite their potent venom and dramatic threat displays, cobras are hunted and eaten by a number of animals, including birds of prey such as secretary birds and eagles, and monitor lizards. The Indian mongoose is famous for killing cobras. Contrary to popular belief, the mongoose is not immune to cobra venom. Instead, the nimble mammal dodges the cobra's strikes until the snake is exhausted. The mongoose kills the cobra by biting and crushing its head. It often eats the snake venom glands and all--swallowed cobra venom is not poisonous. VII COBRAS AND HUMANS A Religion Humans in Africa and Asia have lived alongside cobras for thousands of years. In ancient Egypt, the goddess Wadjet took the form of a cobra and was associated with truth and justice. She was worshiped in Lower Egypt, the region of the northern Nile delta. The cobra also appeared as the uraeus, the rearing cobra symbol of royal power used in the Egyptian pharaoh's crown. The uraeus offered protection for the royal family and for deceased pharaohs during their passage through the underworld. Cobras have played a major role in Indian religion since ancient times. Cobras or nagas were already worshiped as nature deities before the arrival of the IndoEuropean-speaking Aryans around 1500 BC. Hinduism incorporated the local worship of cobras and the cobra deity nag-deva is still widely revered with shrines and roadside temples throughout India. The Hindu festival of Nagapanchami (also spelled Naag Panchami) is held in July or August to honor snakes, most often cobras. According to Buddhist legends, the eyespots on the true cobra's hood are finger marks left from a blessing given by the Buddha. The cobra had protected the Buddha with its hood during a storm or, in another version, had provided shade for the Buddha as he slept. B Asian Traditions Cobras are commonly used in snake charming, an ancient custom still practiced in parts of Asia. The snake charmer appears to make an upright cobra sway to music played on a type of flute. Although snakes can pick up sounds through the ground, the "charmed" cobras are really following the movements of the charmer's hands and flute. In China, cobras have long been used in traditional medicine. They are also eaten in soups and special dishes reputed to have health benefits in cold weather. Wealth from China's booming economy has greatly increased the demand for cobra products and cobra meat. Vietnam has been China's main source for cobras as part of an illegal trade in wildlife. Cobras are often kept on snake farms in Asia to milk them for their venom, which is then used to create serum against snake bites. Snake farms are also popular tourist attractions. In Western countries cobras can be found at many zoos. C Conservation No cobra species are currently considered threatened with extinction. However the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES) lists 11 species of true cobras (genus Naja) and the king cobra as animals on Appendix II, which indicates species that require an export permit for trade. It is likely that some types of cobras thrive because human agriculture increases rodent populations. Loss of forest habitat, however, affects king cobras in some parts of Asia. In most regions of Asia trade in cobra products (hides and traditional medicine) and cobra meat could affect local populations of other types of cobras. Scientific classification: Cobras belong to the family Elapidae. True cobras are in the genus Naja. Water cobras are classified in the genus Boulengerina and burrowing cobras in the genus Paranaja. The king cobra is classified as Ophiophagus hannah. Ringhals are classified as Hemachatus haemachatus. The black desert cobra genus is Walterinnesia. Shieldnose cobras are in the genus Aspidelaps, and tree cobras in the genus Pseudohaje. Microsoft ® Encarta ® 2009. © 1993-2008 Microsoft Corporation. All rights reserved.
