Friday, July 3, 2009

Black Mamba


The Black Mamba (Dendroaspis polylepis), is an elapid snake and is one of Africa's most dangerous and feared snake. It has a wide range of known locations throughout Africa. The black mamba is native to Somalia, Egypt, Ethiopia, Kenya, Tanzania, Botswana, Uganda, Zambia, Zimbabwe, Angola, Namibia, Malawi, Mozambique, South Africa, Swaziland, and the Congo. They inhabit a wide variety of areas that include open savannahs, open woodlands, and rocky outcrops. It is also known for being very aggressive when disturbed or confronted and will not hesitate to strike with deadly precision.

The black mamba is the largest venomous snake in Africa and the second longest venomous snake in the world, after the King Cobra. [1]. Adult black mambas have an average length of 2.5 meters (8.2 ft) and a maximum length of 4.5 meters (~14 ft).[2][3] Like all other reptiles, the black mamba relies on external heat to regulate the temperature of its body.

The Black Mamba is also the fastest land snake in the world, able to reach speeds in excess of 12 miles per hour (20 km/h).[4] However it uses this speed to escape danger, rather than catch prey.

The name "black mamba" is somewhat confusing because that is not the snake's actual color. Its body is not black at all; the name is given to it because of its inky black mouth. Normally, mambas have a dark olive, olive green, grey brown, or metal color. Some of them have a light band around their body. As mambas get older, their skin begins to darken.

Habitat and distribution

The black mamba's habitat consists of savannahs, bushland[6], and outcrops; they have also been known to shelter themselves in termite mounds, hollow trees, and burrows. Many times they have been found in homes.[7] The animal ranges from Somalia to the Democratic Republic of the Congo, including Ethiopia, Kenya, Tanzania, Botswana, Uganda, Zambia, Zimbabwe, Angola, Malawi, Namibia, Mozambique and South Africa.[7] They are considered common in all of these countries.


Behaviour

Warm-blooded prey, such as rodents, ground squirrels, and other small mammals, are the mamba's main source of food. When hunting small animals, the black mamba delivers one or two deadly bites and backs off, waiting for the neurotoxin in its venom to paralyze the prey.[5] When killing a bird, however, the black mamba will cling to its prey, preventing its departure. Black mambas have also been said to have eaten other reptiles and snakes but there is little documentation to support it.[2] After ingestion, powerful acids digest the prey, sometimes within 8 to 10 hours.[8] When warding off a bigger threat or feeling very threatened, the black mamba usually delivers multiple strikes, injecting its potent neuro- and cardiotoxin with each strike, often attacking the body or head, unlike most other snakes. It can strike up to 12 times in a row. A single bite from a black mamba can inject enough venom to kill up to 10–25 grown men, easily killing one unless the appropriate antivenom is administered in time. When cornered, it will readily attack. When in the striking position, the mamba flattens its neck, hisses very loudly and displays its inky black mouth and fangs. It can rear up around one-third of its body from the ground, which allows it to reach heights of approximately four feet.

If left undisturbed, black mambas tend to live for long periods of time in their lairs, which are often vacated insect mounds or hollow trees. Although they are not arboreal, they can sometimes be found in trees. They also often have permanent basking spots they return to daily. Typically, when a black mamba senses danger, it will quickly slither away to the nearest hiding spot.

Black mambas show little difference from the common methods of communication and perception found in all other snakes. They use their eyesight to detect motion, and sudden movements will cause them to strike. The tongue of the mamba is extended from the mouth to collect and analyze air particles which are then deposited in the vomeronasal organ on the roof of the mouth. This organ acts as a chemosensor. These snakes have no external ears, but are quite skilled at detecting vibrations from the ground. Just like other snakes, they will display aggression with a set of signals, warning the possibility of attack if threatened.

Breeding

Breeding usually takes place in late spring or early summer. After mating the male will return to its own home. The female will then lay between 10 and 25 eggs. The offspring are independent as soon as they are born.



Breeding takes place when the two mambas twist their bodies together and can last for days. Females wait approximately 55 days before laying eggs. Female offspring are not bigger than male offspring.



Venom

Black mamba venom contains powerful, fast-acting neurotoxins and cardiotoxins, including calciseptine. Its bite delivers about 100–120 mg of venom on average; however it can deliver up to 400 mg. If the venom reaches a vein, 0.25 mg/kg is sufficient to kill a human in 50% of cases. The initial symptom of the bite is local pain in the bite area, although not as severe as snakes with hemotoxins. The victim then experiences a tingling sensation in the mouth and extremities, ptosis, diplopia (double vision), dysphagia, tunnel vision, ophthalmoparesis, severe confusion, dysarthria, fever, diaphoresis (excessive perspiration), excessive salivation (including foaming of the mouth and nose), and pronounced ataxia (lack of muscle control). If the victim does not receive medical attention, symptoms rapidly progress to severe abdominal pain, nausea and vomiting, lymphadenopathy, dyspnea (shortness of breath), epistaxis, pallor, shock, nephrotoxicity, cardiotoxicity, and paralysis. Eventually, the victim experiences convulsions, respiratory arrest, coma, and then death. Without antivenom, the mortality rate is nearly 100%, the highest among venomous snakes. Depending on the nature of the bite, death can result at any time between 15 minutes and 3 hours. Factors associated with the nature of the bite include penetration of one or both fangs, amount of venom injected, location of the bite, and proximity to major blood vessels. The health of the snake and the interval since it last used its venom mechanism may also be factors. The health, size, age, and psychological state of the individual bitten is also a determining factor.

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