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Black mamba

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For other uses, see Black mamba (disambiguation).

Black mamba
Scientific classification
Kingdom:
Animalia
Phylum:
Chordata
Class:
Reptilia
Order:
Squamata
Suborder:
Serpentes
Family:
Elapidae
Genus:
Dendroaspis
Species:
D. polylepis
Binomial name
Dendroaspis polylepis

The Black mamba (Dendroaspis polylepis) is the longest venomous snake in Africa, averaging around 2.5 meters (8.2 ft), and sometimes growing up to 4.3 meters (14 ft). Apart from being considered as one of the world's deadliest snakes,[2] the Black mamba is also one of the most feared snakes in Africa due to its potent venom, large size, and the ferocity of its attacks.[3] Its name is derived from the black coloration inside the mouth; the actual color of the skin varies, from dull yellowish-green to a gun-metal gray. It is one of the fastest snakes in the world, capable of moving at 4.5 to 5.4 meters per second (16–20 km/h, 10–12 mph).[1]

Taxonomy

In the past, the Eastern green mamba, Dendroaspis angusticeps, and the Black mamba, Dendroaspis polylepis were recognized as one species, until 1946 when Fitzsimon split them into separate species. [4]

Etymology

The snake's scientific name is Dendroaspis polylepis: Dendroaspis meaning "tree asp" and Polylepis meaning "many scaled." The name "Black mamba" is given to the snake not because of its body color but because of its ink-black mouth.[1] It displays this physical attribute when threatened.[1]

Description

Despite its name, the Black mamba does not have a black appearance. The Black mamba's back skin color is actually olive, brownish, gray, or sometime khaki in color. [5] The belly is either a pale gray or pale green color. [6] The Black mamba is a large, streamlined snake with a coffin-shaped head and smooth scales.[6] The adult Black mamba's length is on average 2.5 meters (8.2 ft).[1] However, the Black mamba has been known to reach lengths of 4.3 to 4.5 meters (14 to 15 ft) [7] They weigh on average about 1.6 kilograms (3.5 lb).[1] The Black mamba is the second longest venomous snake in the world, which is only exceeded in length by the King Cobra. Also, it has the most forward pointing fangs of any serpent, which is indicative of the family Elapidae.[7] These fangs are replaced whenever needed.[7] The snakes also has an average life span of 11 years in the wild.[1]

Distribution

The Black mamba lives in Africa, occupying the following range: Northeast Zaire, South-western Sudan to Ethiopia, Eritrea, Somalia, Kenya, Eastern Uganda, Tanzania, southwards to Mozambique, Malawi, Zambia, Zimbabwe and Botswana to Natal in South Africa, and Namibia; then northeasterly through Angola to South-eastern Zaire.[8] Also, the Black mamba is not commonly found above altitudes of 1000 meters (3280.8 feet) ; although, the distribution of Black mamba reaches 1800 meters (5905.5 feet) in Kenya and 1650 meters (5413.3 feet) in Zambia.[8] The Black mamba has also been recorded in West Africa in a region of Dakar, Senegal, in 1954.[8] However, this observation, and a subsequent observation that identified a second specimen in the region in 1956, has not been noted and thus the snake's distribution here is inconclusive.[8] The Black mamba’s distribution is filled with gaps in the Central African Republic, Chad, Nigeria, and Mali. These gaps could lead physicians to misidentify the Black mamba and administer an ineffective anti-venom.[8]

Habitat

The Black mamba has adapted to a variety of climates ranging from savannas, woodlands, rocky slopes, dense forests, and even humid swamps of Africa.[7] The grassland and savanna woodland / shrubs that extend through central and western Africa are the Black mamba’s typical habitat.[8] The Black mamba prefers more arid environments such as light woodland, rocky outcrops, and semi-arid dry bush country.[8]

Environmental Encroachment

The Sugarcane fields that are dominating the habitat of the Black mamba

The Black mamba's environment is rapidly diminishing. In Swaziland alone, 75% of the population is employed by subsistence farming.[9] Because of agricultural encroachment on the Black mamba's habitat, the snake is commonly found in sugarcane fields. The Black mamba will climb to the top of the sugarcane to bask in the sun, and possibly, wait for prey. The majority of human attacks occur in the sugarcane fields, as thousands of workers must plow the fields by hand. This encroachment on its territory contributes to potentially dangerous human contact with these venomous snakes.[1] Nearly 20,000 people die of snakes bites each year, and the residents of Swaziland and Southern Africa have suffered for generations.[10]

Behavior

The Black mamba uses its incredible speed to escape threats, not to hunt prey.[1] The Black mamba is capable of reaching speeds up to 20 kilometers per hour (12 mph), traveling with up to a third of its body raised off the ground.[1] Over long distances the Black mamba travels 11 to 19 kilometers per hour (6.8 to 11.8 mph), but in short bursts the Black mamba reaches the speed of 23 kilometers per hour (14 mph). [11] Therefore, the Black mamba is the fastest land snake.[12] The Black mamba is shy and secretive; it will always seeks to escape when confronted.[1] When the snakes are cornered, they mimic a cobra by spreading a neck-flap, exposing their black mouths, and hissing.[1] If this attempt to scare away the attacker fails, the Black mamba will strike repeatedly injecting gratuitous amounts of venom.[1] The Black mamba spends long periods of time in its layer or den.[7] The Black mamba is normally docile, gentle, and poses no harm unless it feels threatened, senses something has entered its territory, or notices sudden movements around itself.[7] The Black mamba is a diurnal snake.[12]Though the Black mamba's scientific name seems to be indicative of tree climbing, the Black mamba is rarely an arboreal snake. [12]

Hunting and Prey

The Black mamba commonly feeds on species of birds and rats; it even preys on hyraxes.[7] Black mambas have also been known to prey on bushbabies, bats, and chickens. [4] At birth, the Black mamba begins to immediately prey on organisms as large as a rat.[7] Though it is not commonly observed, the Black mamba may consume termites , as the mounds are commonly used by the Black mamba.[7] Once the Black mamba has found a prey, it strikes the prey repeatedly. Nonetheless, it lets the prey go until the neurotoxins take effect. Birds are an exception: the Black mamba does not release its hold on birds because they will fly away.[7]

Reproduction

Breeding occurs in either spring or early summer.[7] A female can lay anywhere from 10 to 25 eggs, which are usually laid in decaying vegetation because it provides insulation for the eggs.[7] The gestation period is between 80 to 90 days.[6] At birth, a young Black mamba is around 1 to 2 feet (0.30 to 0.61 m) long.[13] Immediately, the offspring become independent.[7] In about a year, the offspring will grow to reach a length of 2 meters (6 ft 7 in).[6]

Venom

The venom of the Black mamba consists mainly of neurotoxins with a LD50 of 0.25 mg/kg.[14] Its bite delivers about 100–120 mg of venom on average; however, it can deliver up to 400 mg. 10 to 15 mg is deadly to a human.[7] The mortality rate is nearly 100%, unless the snakebite victim is promptly treated with antivenom.[1] Black mamba bites can potentially kill a human within 20 minutes, but death usually occurs after 30–60 minutes, sometimes taking up to three hours (depending on the health, size, age, psychological state of the human, the penetration of one or both fangs from the snake, amount of venom injected, location of the bite, and proximity to major blood vessels.[1] The health of the snake and the interval since it last used its venom mechanism is also important). Nowadays, there is a polyvalent antivenom produced by SAMIR (South African Institute of Medical Research) to treat all Black mamba bites from different localities.[15]

Because of its highly potent venom, its temperament, and its speed, the Black mamba is widely regarded as one of the most dangerous snakes in Africa. However, humans bitten by a Black mamba are rare, as the snake would rather avoid confrontation with humans.[1]

If bitten, common symptoms to watch for are rapid onset of dizziness, coughing or difficulty breathing, and erratic heartbeat.[15] In extreme cases, when the victim has received a large amount of venom, death can result within an hour from respiratory or cardiac arrest.[15] Also, the Black mamba's venom has been known to cause paralysis.[15] Death is due to suffocation resulting from paralysis of the respiratory muscles.[15]

The Black mamba’s venom is dendrotoxin. The toxin disrupts the exogenous process of muscle contraction of the sodium potassium pump. First, the toxin causes the release of neurotransmitters at peripheral synapses. Then, the dendrotoxin causes repetitive depolarization in both motor and sensory neurons. This rapid activation of each neuron leads to epileptic activity. Finally, the dendrotoxin blocks potassium channels, stopping the movement of calcium. Therefore calcium levels are unregulated leading to muscular paralysis and eventually death.[7] An example of the potency of the venom is seen through the records of mice. Normally, the death time of a mouse after subcutaneous injection of many toxins is around 7 minutes. However, the Black mamba venom killed the mouse in 4.5 minutes.[3]

Predators

The Yellow mongoose is just one of the many animals that prey on Black mamba eggs

Mongooses are the main predators of the Black mamba. They usually prey on young snakes and eggs. Mongooses are notable due to their resistance to snake toxins. This resistance is caused by mutations in their Nicotinic acetylcholine receptor. These mutations prevent the neurotoxin present in snake venom from binding the to receptor. Therefore, it prevents the associated toxicity [16]. Because of the mongooses' resistance to snake venom, adult mambas have trouble fighting them off.[2] Although, mongooses seldom attack an adult as they are too large for the mammals to kill with ease. Cape file snakes are also predators of young Black mambas. [4] Predatory birds, such as the secretary bird or large species of eagles, prey on adult Black mambas.[7]

Gallery

  • Black mamba at Wilmington's Serpentarium.
    Black mamba at Wilmington's Serpentarium.
  • Close-up of a Black mamba's head
    Close-up of a Black mamba's head
  • Close-up of the snake climbing a branch, in London Zoo.
    Close-up of the snake climbing a branch, in London Zoo.
  • A Black mamba at the St Louis zoo.
    A Black mamba at the St Louis zoo.

References

  1. ^ a b c d e f g h i j k l m n o p "Black mamba". National Geographic Society. Retrieved 2010-03-12.
  2. ^ a b The new encyclopedia of Reptiles --"Africa's Serpent". Time Book Ltd. 2002.
  3. ^ a b Strydom, Daniel (1971-11-12). "Snake Venom Toxins" (PDF). The Journal of Biological Chemistry. Retrieved 2010-04-24.
  4. ^ a b c Haagner, G.V; Dr. Morgan (1993). "The maintenance and propagation of the Black mamba Dendroaspis polylepis at the Manyeleti Reptile Centre, Eastern Transvaal" (PDF). International Zoo Yearbook. Zoological Society of London. Retrieved 2010-05-19.{{cite web}}: CS1 maint: multiple names: authors list (link)
  5. ^ Mattison, Chris (1987-01-01). Snakes of the World. New York, New York: Facts on File, Inc. p. 164.
  6. ^ a b c d "Black Mamba". Kruger National Park. Retrieved 2010-05-18.
  7. ^ a b c d e f g h i j k l m n o p Shah, Atif. "Black Mamba" (PDF). Sambhota Tibetan Schools Society. Retrieved 2010-05-03.
  8. ^ a b c d e f g Håkansson, Thomas (1983-01-01). "On the Distribution of the Black mamba (Dendroaspis polylepis) in West Africa". Journal of Herpetology. Society for the Study of Amphibians and Reptiles. Retrieved 2010-05-16. {{cite web}}: Unknown parameter |coauthors= ignored (|author= suggested) (help)
  9. ^ "UNDP: Human development indices – Table 3: Human and income poverty (Population living below national poverty line (2000-2007))" (PDF). United Nations Development Programme. 28 November 2008. Retrieved 29 December 2009.
  10. ^ Litschka-Koen, Thea (2009-11-08). "Antivenom Swazi". Antivenom Swazi Foundation. Retrieved 2010-04-18.
  11. ^ Richardson, Adele. Mambas. Mankato, Minnesota: Capstone Press date = 2004. p. 13. Retrieved 2010-05-19. {{cite book}}: Missing pipe in: |publisher= (help); Text "web" ignored (help)
  12. ^ a b c Maina, J.N (1989-12). "The morphology of the lung of the black mamba Dendroaspis polylepis" (PDF). The Journal of Anatomy. Retrieved 2010-05-19. {{cite web}}: Check date values in: |date= (help)
  13. ^ Richardson, Adele. Mambas. Mankato, Minnesota: Capstone Press date = 2004. p. 5. Retrieved 2010-05-19. {{cite book}}: Missing pipe in: |publisher= (help); Text "web" ignored (help)
  14. ^ "LD50 Menu". Retrieved 2010-04-21.
  15. ^ a b c d e Davidson, Terence. "IMMEDIATE FIRST AID". Iniversity of California, San Diego. Retrieved 2010-05-12.
  16. ^ Asher, O (1998-06-04). "Functional characterization of mongoose nicotinic acetylcholine receptor alpha-subunit: resistance to alpha-bungarotoxin and high sensitivity to acetylcholine" (PDF). PubMed.gov. Retrieved 2010-05-19.

External links

Media related to Dendroaspis polylepis at Wikimedia Commons

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