Deadly Black mamba

black mamba

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). Its name is derived from the black colouration inside the mouth rather than the actual colour of the skin which varies from dull yellowish-green to a gun-metal grey. It is the fastest snake in the world, capable of moving at 4.32 to 5.4 metres per second (16–20 km/h, 10–12 mph).

Description
The black mamba's back skin colour is olive, brownish, gray, or sometimes khaki.[5] The adult snake's length is on average 2.5 meters (8.2 ft),[1] but some specimens have reached lengths of 4.3 to 4.5 meters (14 to 15 ft).[5] Black mambas weigh about 1.6 kilograms (3.5 lb).[1] on average. The species is the second longest venomous snake in the world, exceeded in length only by the king cobra.[5] The snake has an average life span of 11 years in the wild.[1]

Habitat
The black mamba has adapted to a variety of climates ranging from savanna, woodlands, rocky slopes, dense forests and even humid swamps.[6] The grassland and savanna woodland/shrubs that extend through central, eastern and southern Africa are the black mamba's typical habitat.[6] The black mamba prefers more arid environments such as light woodland, rocky outcrops, and semi-arid dry bush country.

Behaviour

The black mamba uses its speed to escape threats, not to hunt prey.[1] It is known to be capable of reaching speeds of around 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 can travel 11 to 19 kilometers per hour (6.8 to 12 mph), but in short bursts it can reach a speed of 16 to 20 kilometers per hour (9.9 to 12 mph),or even 23 kilometers per hour (14 mph) [8] making it the fastest land snake.[9] It is shy and secretive; it always seeks to escape when a confrontation occurs.[1] If a black mamba is cornered it mimics a cobra by spreading a neck-flap, exposing its black mouth, and hissing.[1] If this endeavor to scare away the attacker fails, the black mamba may strike repeatedly.[1] The black mamba is a diurnal snake. Although its scientific name seems to be indicative of tree climbing, the black mamba is rarely an arboreal snake.[9] These snakes retreat when threatened by predators.

Venom

The venom of the black mamba consists mainly of potent neurotoxins[10]. With a LD50 of 0.25 mg/kg—0.32 mg/kg, the black mamba's venom is virulently toxic.[11] Some of the components of the venom have a much more toxic LD50 value than the venom as a whole, for example α-dendrotoxin (or "Toxin 1") and γ-dendrotoxin (or "Toxin 7") had subcutaneous LD50 values of 0.09 µg and 0.12 µg per gram of white mice, respectively.[12] Although only 10 to 15 mg[13] is deadly to a human adult, its bite delivers about 100–120 mg of venom on average[13], but they can deliver up to 400 mg of venom in a single bite[13]. It is reported that before the antivenom was widely available, the mortality rate from a bite was 100%.[14][15][16][17][1][18] Black mamba bites can potentially kill a human within 20 minutes or less[19][20][13][12] depending on the nature of the bite and the area bitten, but death usually occurs after 30–60 minutes on average, sometimes even taking up to three hours. British wildlife enthusiast Nathan Layton was bitten near Hoedspruit by a juvenile black mamba and died less than 30 minutes after being bitten.[21] The fatality duration and rate depend on various factors, such as 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. Presently, there is a polyvalent antivenom produced by SAIMR (South African Institute for Medical Research) to treat all black mamba bites from different localities.[18]

If bitten, common symptoms for which to watch are rapid onset of dizziness, coughing or difficulty breathing, and erratic heartbeat.[18] In extreme cases, when the victim has received a large amount of venom, death can result within minutes[1] from respiratory or cardiac arrest.[18] This is especially true if the victim is bitten in the face or chest area, as a black mamba can rear up around one-third of its body from the ground which puts it at about four feet high. When warding off a threat, the black mamba delivers multiple strikes, injecting large amounts of virulently toxic venom with each strike, often landing bites on the body or head, unlike other snakes. Also, the black mamba's venom has been known to cause paralysis.[18] Death is due to suffocation resulting from paralysis of the respiratory muscles.[18]

Many herpetologists, including South African-born herpetologist Austin Stevens, regard the black mamba as one of, if not the most dangerous and feared snakes in the world due to various factors including the toxicity and high yield of its venom, its high level of aggression, its speed, agility, size, and other factors.[22][12] Nevertheless, attacks on humans by black mambas are rare, as the snakes usually avoid confrontation with humans and their occurrence in highly-populated areas is not very common compared with some other species. 
 Toxin

Mamba venom is made up mostly of dendrotoxins (dendrotoxin-k - "Toxin K"[23], dendrotoxin-1 - "Toxin 1"[24], dendrotoxin-3 - "Toxin 3"[25], dendrotoxin-7 - "Toxin 7"[25]), and calciseptine[26]. The dendrotoxins disrupt the exogenous process of muscle contraction by means of the sodium potassium pump. Toxin K is a selective blocker of voltage-gated potassium channels[27], Toxin 1 inhibits the K+ channels at the pre and post-synaptic level in the intestinal smooth muscle. It also inhibits Ca2+-sensitive K+ channels from rat skeletal muscle‚ incorporated into planar bilayers (Kd = 90 nM in 50 mM KCl)[28], Toxin 3 inhibits M4 receptors, while Toxin 7 inhibits M1 receptors.[25] The calciseptine is a 60 amino acid peptide which acts as a smooth muscle relaxant and an inhibitor of cardiac contractions. It blocks K+ induced contraction in aortic smooth muscle and it blocks spontaneous contraction of uterine muscle and portal vein.[29][13] The venom is highly specific and virulently toxic. In an experiment, the death time of a mouse after subcutaneous injection of some toxins studied is around 7 minutes. However, a black mamba venom can kill a mouse after 4.5 minutes.[12]

 Hunting and prey

As stated, the black mamba is diurnal. It is an ambush predator that waits for prey to get close.[8] If the prey attempts to escape, the black mamba will follow up its initial bite with a series of strikes.[8] When hunting, the black mamba has been known to raise a large portion of its body off the ground.[8] The black mamba will release larger prey after biting it, but smaller prey, such as birds or rats, are held onto until the prey's muscles stop moving.[8] They have been known to prey on bushbabies, bats, and small chickens.

black mamba attacking