|A black mamba in a defensive posture|
The black mamba (Dendroaspis polylepis), also called the common black mamba or black-mouthed mamba, is a highly venomous snake of the genus Dendroaspis (Mambas), and is endemic to sub-Saharan Africa. It was first described in 1864 by Albert Günther, a German-born British zoologist, ichthyologist, and herpetologist. It is the longest species of venomous snake in Africa and the second longest venomous snake in the world, averaging around 2.2 to 2.7 m (7.2 to 8.9 ft) in length, and sometimes growing close to lengths of 4 m (13 ft). The longest recorded black mamba was 4.3 m (14 ft).
Black mambas are one of the most feared snake species in the world, and certainly the most feared in Africa. One snake expert called this species "death incarnate". Its combination of speed, unpredictable aggression, and potent venom make it an extremely dangerous species. It is the fastest snake in the world, capable of moving at 4.32 to 5.4 metres per second (11–19 km/h, 10–12 mph) for short distances. The black mamba has a reputation for being very aggressive, but like most snakes, it usually attempts to flee from humans unless threatened.
It has one of the most highly potent and rapid-acting venom of any snake, and in cases of severe envenomation, it is capable of killing an adult human in as little as 20 minutes. Two such cases have been documented in the medical literature. In one such case, an adult male was bitten on his right arm, just above the wrist by a black mamba which was estimated to be approximately 2.5 m (8.2 ft) in length. The victim began to show signs of prominent neurotoxicity within minutes. At ten minutes post-envenomation, respiratory paralysis set in and 20 minutes post-envenomation the victim showed no signs of life and was deceased. Other cases of rapid death, within 30-60 minutes are relatively common among this species. However, depending on the nature of the bite, death time can be anywhere from 20 minutes to 6-8 hours. Black mamba venom can kill a mouse after 4.5 minutes, the shortest time among all known venomous snakes. The second shortest time to kill a mouse on record was between 7-8 minutes via a coastal taipan envenomation. Without rapid and vigorous antivenom therapy, a bite from a black mamba is almost always rapidly fatal. Many experts regard this as the world's most dangerous snake.
- 1 Etymology
- 2 History
- 3 Biology
- 4 Distribution and habitat
- 5 Behaviour and ecology
- 6 Venom, envenomation and antivenom
- 7 Relationship with humans
- 8 References
- 9 Further reading
- 10 External links
Dendroaspis polylepis has been the name of the black mamba's binomial name since 1864. The generic name, Dendroaspis, is derived from Ancient Greek words – Dendro, which means "tree", and aspis (ασπίς) or "asp", which' is understood to mean "shield", but it also designate "cobra" or simply "snake". In old text, aspis or asp was used to refer to Naja haje (in reference with the hood, like a shield). Thus, "Dendroaspis" literally means tree snake, which refers to the arboreal nature of most of the species within the genus. Schlegel used the name Dendroaspis, significant tree cobra. The specific name polylepis, is also derived from the Greek words - poly or polus, simply means "many" or "more" and lepis, also Greek in origin, means "scales", therefore "polylepis" literally means "many-scales". This refers to the black mambas size and the many scales it has. The name "black mamba" is given to the snake not because of its body colour but because of the ink-black colouration of the inside of its mouth, which it displays when threatened.
Evolution and taxonomy
The black mamba is classified under the genus Dendroaspis of the family Elapidae. The genus was described by the German ornithologist and herpetologist Hermann Schlegel in 1848. Initially, they were grouped within the Naja genus, but later removed due to the fact that they don't belong to the "cobra group". Parsimony analysis of phylogenetic relationships among elapines was found to be divided into two clades: coral snakes vs cobras, Bungarus, Elapsoidea, and Dendroaspis. The term cobra has traditionally been applied to the genera Aspidelaps, Boulengerina, Hemachatus, Naja, Ophiophagus, Paranaja, Pseudohaje, and Walterinnesia, a mostly African group generally characterized by the ability to flatten the neck into a hood when threatened. The African mambas (Dendroaspis) also have the ability to spread a hood when threatened, albeit more weakly than many members of the aforementioned group. Studies found significant bootstrap support for a core cobra group consisting of Naja, Boulengerina, Paranaja, Aspidelaps, Hemachatus, and Walterinnesia. Oddly, the Asian king cobra (Ophiophagus hannah), was not part of this clade, clustering instead with a group including Dendroaspis and Bungarus on the most-parsimonious tree or with Elapsoidea on the maximum-likelihood tree. This result calls into question the monophyly of cobras and underscores the uncertainty of the homology of the hood spreading behavior in cobras and mambas. The relationships of Dendroaspis, Ophiophagus, and Bungarus differed between the parsimony and likelihood analyses, suggesting that more work is necessary to resolve the relationships of these problematic taxa.
The black mamba is one of four species in the African snake genus Dendroaspis that are known as mambas. The species was first described in 1864 by Albert Günther, a German-born British zoologist, ichthyologist, and herpetologist. Soon after, a subspecies was identified, Dendroaspis polylepis antinorii (Peters, 1873), but this is no longer accepted as distinct. According to Broadley and Howell (1991), D. polylepis antinorii is synonymous with D. polylepis. In 1896, zoologist George Albert Boulenger combined the species (Dendroaspis polylepis) as a whole with the eastern green mamba, (Dendroaspis angusticeps), and they were considered a single species from 1896, until 1946, when Dr. Vivian FitzSimons split them into separate species.
Identification and physical appearance
The adult black mamba's back skin colour is olive, brownish, gray, or sometimes khaki. A young snake is lighter, but not light enough to be confused with the different species of green mamba. Its underbody is cream-coloured, sometimes blended with green or yellow. Dark spots or blotches may speckle the back half of the body, and some individuals have alternating dark and light scales near the posterior, giving the impression of lateral bars. The inside of the mouth is dark blue to inky black. Its body is long and slender and it's head, which readily stands out from the body, is said to be shaped like a coffin.. It is a proteroglyphous snake, meaning it has immovable, fixed fangs at the front of the maxilla. The eyes are dark brown to black, with a silvery-white to yellow edge on the pupils. As they age, their colouration tends to get darker.
The species is the second-longest venomous snake in the world, exceeded in length only by the king cobra. Not all scientific sources agree on the range of lengths for this species, but adult specimens are 2.2 to 2.7 m (7.2 to 8.9 ft) in length on average, with a range of 2.0 to 3.8 m (6.6 to 12 ft). Some sources report maximum lengths of 4.3 to 4.5 m (14 to 15 ft). In the 1950s, a black mamba measuring 4.3 m (14 ft), known as "the King of the Mambas" in African Wildlife, was shot in Natal, South Africa. There is no real sexual dimorphism, and both male and female snakes of this species have a similar appearance and tend to be similar in size. Information regarding the lifespan of snakes in the wild is sparse; the longest recorded lifespan of a captive black mamba is 14 years, but actual maximum lifespans could be much greater.
|Dorsal at midbody||Ventral||Subcaudal||Anal plate||Upper labials||Upper labials to eye||Preoculars||Postoculars||Lower labials||Temporal|
|23-25 (rarely 21)||248–281||109–132 (paired)||Divided||7-10||4th (or 3rd to 4th)||3-4 (2-5)||3 (can be 4)||11-13 (10-14)||2+3 (variable)|
Black mambas breed only once a year. The breeding season begins in the spring, which occurs around the month of September in the African regions where these snakes occur, as much of sub-Saharan Africa is in the Southern Hemisphere. In this period, the males fight over females. Agonistic behaviour for black mambas involves wrestling matches in which opponents attempt to pin each other's head repeatedly to the ground. Fights normally last a few minutes, but can extend to over an hour. The purpose of fighting is to secure mating rights to receptive females nearby during the breeding season. Beyond mating, males and females do not interact. Males locate a suitable female by following a scent trail. Upon finding his mate, he will thoroughly inspect her by flicking his forked tongue across her entire body. Males are equipped with two hemipenes. After a successful and prolonged copulation, the eggs develop in the female's body for about 60 days. During this period, the female seeks a suitable place to lay the eggs. Females prefer using abandoned termite mounds as nests. Mature females lay between 15 and 25 eggs, which they hide very well and guard very aggressively. The eggs incubate for about 60 days before hatching. The hatchlings are about 50 centimetres (20 in) in length and are totally independent after leaving the eggs, hunting and fending for themselves from birth. Young hatchlings are as venomous as the adults, but do not deliver as much venom per bite as an adult snake would. Unlike adults who carry about 8-16 ml of venom in their glands, young hatchlings carry only 1–2 ml of venom in their venom glands, which is sufficient quantity for a lethal effect on a human.
No specific information was available for this species regarding the hatchlings development, but some general assumptions can be made. Black mambas are oviparous. Young incubate inside the eggs for 2 to 3 months after being deposited. They break through the shell with an "egg-tooth". Upon hatching, young are fully functional and can fend for themselves. They have fully developed venom glands (that carry 1-2 ml of venom, which is sufficient to kill an adult human), and are dangerous just minutes after birth. The yolk of the egg is absorbed into the body and can nourish the young for quite some time.
Distribution and habitat
Although it is a large diurnal snake, the distribution of the black mamba is the subject of much confusion in research literature, indicating the poor status of African herpetological zoogeography. However, the distribution of the black mamba in eastern Africa and southern Africa is well documented. Pitman (1974) gives the following range for the species' total distribution in Africa: northeastern Democratic Republic of the Congo, southwestern Sudan, South Sudan to Ethiopia, Eritrea, Somalia, southern Kenya, eastern Uganda, Tanzania, southwards to Mozambique, Swaziland, Malawi, Zambia, Zimbabwe and Botswana to KwaZulu-Natal in South Africa, and into Namibia; then northeasterly through Angola to the southeastern part of the Democratic Republic of Congo. According to WHO, the species is also found in Rwanda. The black mamba is not commonly found above altitudes of 1,000 metres (3,300 ft), although the distribution of black mamba does reach 1,800 metres (5,900 ft) in Kenya and 1,650 metres (5,410 ft) in Zambia. The black mamba was recorded in 1954 in West Africa in the Dakar region of Senegal. However, this observation, and a subsequent observation that identified a second specimen in the region in 1956, have not been confirmed and thus the species' distribution in West Africa is inconclusive. The black mamba's western distribution contains gaps within the Central African Republic, Chad, Nigeria and Mali. These gaps may lead physicians to misidentify the black mamba and administer an ineffective antivenom. West of Ethiopia, it has a curious distribution, with few records. There is a single record from the Central African Republic, two from Burkina Faso, and as mentioned two unconfirmed sightings from Senegal, one from the Gambia, and a possible sighting in Cameroon. These sightings may indicate improper documentation, remaining populations from what was once a larger range, or new populations, indicating a growing range.
The black mamba has adapted to a variety of climates, ranging from savanna, woodlands, farmlands, rocky slopes, dense forests and humid swamps. The grassland and savanna woodland/shrubs that extend all the way from southern and eastern Africa to central and western Africa are the black mamba's typical habitat. The snake prefers more arid environments, such as semiarid, dry bush country, light woodland, and rocky outcrops. This species likes areas with numerous hills, as well as riverine forests. Black mambas often make use of abandoned termite mounds and hollow trees for shelter, which it goes back to everynight. The abandoned termite mounds are especially used when the snake is looking for somewhere to cool off, as the mounds are sort of a "natural air-conditioning" system. The structure of these mounds is very complex and elaborate. They have a network of holes, ducts, and chimneys that allow air to circulate freely, drawing heat away from the nest during the day – though without taking too much valuable moisture – while preventing the nest cooling too much at night. As a species which maintains a permanent home range throughout its entire life, the black mamba will always return to its lair at night within this home range if left undisturbed.
This species is classified as Least Concern (LC) on the IUCN Red List of Threatened Species (v3.1, 2011). The conservation status of this species was last assessed in June 2009 and published in 2010, and it was classed as such due to its very large distribution. Besides its very large geographical distribution, the species has no specific threats that have been reported, and this species is not undergoing significant population declines. This species is regarded as common in sub-Saharan Africa, it has been found as far north as Senegal and as far south as northeast South Africa. Trape (2005) reports this species as far west as Senegal and Guinea. The black mamba is reported to be widespread in locations with suitable habitats. In areas with few records this can be attributed to undercollecting rather than low abundance. It is unlikely that any major threat is impacting this species across its full range. Black mambas prefer to stay away from humans. Human population expansion into its habitat could therefore constitute a potential threat to this species. However, the extent of its range throughout much of Africa means that this should not be considered a serious threat. There are no known species-specific conservation measures in place for this species, however, in places its distribution coincides with protected areas. No conservation measures are required for this species.
Behaviour and ecology
Though they prefer traveling on the ground, and they are considered to be a terrestrial species of snake, they can also be arboreal. They are capable of climbing trees with great agility, quickness and ease. Black mambas maintain a home range, but are not considered highly territorial, preferring to flee from danger when threatened. Unless disturbed, black mambas will remain in the same home range for years or even their entire lifespan. They will also find a permanent home or lair usually in an abandoned termite mound, an aardvark burrow, a hollow tree or log, a rock crevice or sometimes even the roof of a home. They prefer to avoid confrontation and will often attempt to retreat to their lair, attacking anything that gets in their way. This usually results when an threat or predator blocks the snake's direct path to its lair or refuge. A cornered black mamba will quickly become defensive, and display highly aggressive behaviour, often with deadly intent. They will raise their head far off the ground (up to a metre above ground), open its mouth agape to display the inner black mouth lining, expand a narrow hood, flick their tongue, hiss loudly, and make mock charges forward towards the threat. They will maintain this defensive posture, staying very alert, keeping a close eye on the threat and making mock charges. Any sudden movements by the threat will cause the mamba to make a full on attack. If the attempt to scare away the threat fails, it will strike repeatedly. If the threat slowly moves away from the mamba, the snake will usually retreat. Strikes will be numerous and extremely rapid, and are often fatal to humans. There is a case in literature in which a man was bitten twice in rapid succession on a motorcycle as he accidentally went over a black mamba. Those two rapid bites proved to be fatal to the man. A diurnal species, the black mamba is usually active from a few hours after sunrise until about an hour before dusk. Being reliant on external heat sources to maintain its body temperature, black mambas spend a lot of their time basking in the sun and unless disturbed, will return to a permanent basking spot, usually a short tree branch, a log, or even a large rock. After basking in the sun for a few hours, they will go on the move begin to actively seek prey, swiftly moving through their home range with their heads held up above ground. The black mamba can travel 11 to 19 km/h (6.8 to 12 mph), making it the fastest land snake in the world. Although it can reach a maximum of approximately 19 km/h (12 mph), it can only maintain such speeds for short distances, anywhere from 50 to up to 80 metres before it begins to tire and a considerable drop in speed is seen. Besides the relatively high speed with which it moves, the black mamba can strike accurately in any direction, even while moving fast. In striking, it throws its head upward from the ground for about two-fifths the lengths of its body.
Unless completely cornered by a threat with no way to escape, the black mamba will generally make a quick escape when confronted and not stand its ground. However, many scientists have taken notice of attacks from this species that that come with no prior warning signals and no apparent provocation. It is one of the few venomous snake species of the world, or perhaps the only venomous snake species, that will attack without prior warning signals or provocation. This behaviour, though not typical, has been noted in both captive and wild black mambas. As a result, many snake experts have cited the black mamba as the world's dealiest and most aggressive snake, noting this tendency to attack without any provocation. It can show an incredible amount of tenacity, fearlessness, and aggression when cornered, during breeding season, or when defending its lair. According to Swaziland-born snake handler and snake expert Thea Litschka-Koen:
Black mambas will kill a dog or several dogs if threatened and it happens quite often. We also find dead cows and horses! We were called by the frantic family late one evening. When we arrived minutes later, two small dogs had already died and two more were showing severe symptoms of envenomation. Within 15 minutes we had found and bagged the snake. By this time the other two dogs were also dead. The snake must have been moving through the garden when it was attacked by the dogs. It would have struck out defensively, biting all the dogs that came within reach. The snake was bitten in several places on its body as well and died about a week later.
— Thea Litschka-Koen
In a different case in which a black mamba was attacked by seven dogs, the snake managed to swiftly envenomate and dispatch all seven dogs without incurring any injuries aside from a few minor and superficial bite wounds on its tail. All seven dogs rapidly succumbed to the mamba's venom, two of the dogs were dead within the first 10-15 minutes, while the others all died, one at a time, in less than an hour. In 2006 the first case of an elephant dying of a snakebite was reported in the October 2006 issue of the journal Applied Animal Behaviour Science. To date, this is the only scientifically documented case of an elephant being killed via snakebite. No other scientifically proven or documented case of an elephant being killed via snakebite exists. On 10 October 2003, sometime between 1:00 pm and 3:00 pm local time, a full grown female African elephant named Eleanor that weighed around 7,500 lb (3,400 kg) at Saraburu National Park in Kenya was bitten by a black mamba. The effects of the venom were rapid, a short time later Eleanor began to slow down, showed an unsteady gait and began to fall behind the rest of the herd, which was highly unusual behaviour for a matriarch, who is always ahead of the herd and leading the way. Not long after, Eleanor fell to the ground and was helped up by another elephant until she fell again and never got up. The bite was fatal to the matriarch, who suffered for a lengthy period of time (just under 24 hours) from the effects of the venom before finally dying. The dramatic images show one elephant, Grace, who was a matriarch of a different herd, struggling to help the 40-year-old matriarch Eleanor, who lay on the ground, languishing in agony and struggling to breath as a result of the black mamba bite. The footage, shot by scientists at Samburu National Reserve in Kenya, show Grace calling out in distress and making desperate attempts to get the dying elephant back onto her feet. Sadly, her efforts were unsuccessful. The next day, 11 October 2003 at around 11:00 am local time, Eleanor's lifeless body was visited by other elephants, who rocked back and forth in mourning or stood silently, paying their last respects. In all five distinct herds or families of elephants visited to dead body of Eleanor to pay respect. This female elephant, Eleanor, was a herd matriarch and it had been being observed by a research team of scientists led by Dr. Iain Douglas Hamiltom from Oxford University's Department of Zoology, and the founder of the Save The Elephants charity and the University of California for many years. Although the first scientifically documented case of an adult elephant dying of a snakebite was remarkable, the team of scientists and the public focused their attention on the behaviours and emotions that were displayed by elephants of different families towards the dying matriarch.
Communication and perception
Black mambas show little deviation from the common methods of communication and perception found in snakes. They primarily rely on their eyesight, their tongue, and ability to sense vibration to gather information from their environment. Their eyes are large and they have excellent eyesight which is used to detect motion, to view surroundings, and to help them carefully navigate and move about in their environment. Detection of quick or sudden movements will cause them to strike immediately. The vomeronasal organ (Jacobson's organ), a chemosensory organ located on the roof of their mouth, is involved in the black mambas social chemical communication and in hunting prey. They collect environment stimuli, such as molecules from the air and nearby objects by extending their forked tongue from their mouth. These chemical elements are then deposited in the vomeronasal organ when the tongue is retracted. They lack external auditory structures and cannot hear airborne sounds, but the part of their body in direct contact with the ground is very sensitive to vibrations; thus they are able to sense other animals approaching by detecting faint vibrations in the air and on the ground. Like many snakes, when threatened, they will become defensive and aggressive, displaying a set of warning signals of a possibility of attack.
Hunting and prey
Black mambas are opportunistic predators. They generally seem to prefer larger sized prey, but will take small prey items as well. Although they mainly feed on warm-blooded mammals and birds, they have also been said to take other snakes. Juvenile black mambas will readily take skinks and lizards. A 2 m (6.6 ft) black mamba has even been observed feeding on flying termite alates. When hunting, the black mamba is often seen travelling with its head raised well above ground level, quickly moving forward in search of prey. Once prey is detected, the black mamba freezes before hurling itself forward and issuing several quick bites, swiftly killing its prey. If the prey attempts to escape, the black mamba will follow up its initial bite with a series of strikes. It will release larger prey after biting it, but smaller prey, such as birds or rats, are held until the prey's muscles stop moving.
Black mambas feed on a variety of prey, especially mammals, including Rock hyraxes (dassies), rats, mice, young Cane rats, Common mole rats, squirrels, bats, bushbabies and elephant shrews. They have also been known to prey on birds and small chickens, as well as other snakes, such as the puff adder and Cape cobra. A large specimen has even been recorded eating a young blue duiker (Philantomba monticola). Although rare, predation on primates by larger sized snakes does occur. In one incident, a black mamba predated on a Sykes monkey (Cercopithecus albogularis albogularis). After ingestion, powerful acids digest the prey, sometimes within 8 to 10 hours.
There are no specific predators of the black mamba, but snakes in general tend to have many. Large adult black mambas have no specific predators other than humans. Humans do not usually consume black mambas; they often kill them out of fear. Other predators will often target eggs or very young mambas, and known predators are large reptiles such as crocodiles or monitors, mongooses, foxes or jackals, and birds of prey. Mamba eggs are also susceptible to being eaten by many types of scavengers. Juvenile mambas are also subject to predation from Cape file snakes.
Venom, envenomation and antivenom
Like many snakes, the venom toxicity (LD50) of individual specimens can show considerable variation which can be due to geographical region, seasonal variation, diet, habitat, and age-dependent change. The venom of the black mamba is a protein of low molecular weight and displays very high activity in terms of hyaluronidases, which is also essential in facilitating propagation of venom components throughout tissue (spreading the venom through the body), as a result the venom is able to spread extraordinarily rapidly within the bitten tissue. It is considered to be the most rapid-acting snake venom. In a study, a mouse injected with an overodse of black mamba toxins subcutaneously, died in 4.5 minutes. Such short death times have never been seen with any other snake venom toxins. The shortest death time for any other snake was in the range of 7–8 minutes, in a mouse which was subcutaneously injected with coastal taipan venom. The venom of this species is one of the most potent snake venoms in the world, and consists mainly of highly potent pre-synaptic and post-synaptic neurotoxins; it also contains cardiotoxins, fasciculins, and calciseptine. Median lethal dose (LD50) values for this species' venom varies tremendously from one toxinological study to the next. Ernst and Zug et al. 1996 listed a value of 0.02 mg/kg for intravenous injection and 0.05 mg/kg for subcutaneous injection. One study showed the intraperitoneal injection LD50 in mice was very toxic: 0.01 mg/kg. In the study, seizure threshold was significantly lowered and the mice went through convulsions. Significant changes in motor activity were observed and there were changes in structure or function of salivary glands. The Australian Venom and Toxin database listed a value of 0.32 mg/kg SC, while Spawls & Branch and Minton & Minton both listed the SC LD50 at 0.28 mg/kg and Brown lists a murine value of 0.12 mg/kg SC. Brown also conducted venom toxicity studies on monkeys, who were given subcutaneous injections of venom. The results indicated that black mamba venom was the most toxic to monkeys (LD50 0.11 mg/kg, ranking first among all snake venoms that were tested. It was more toxic than the Inland taipan (0.47 mg/kg), Eastern brown snake (0.49 mg/kg), and Coastal taipan (0.24 mg/kg). In the same study on monkeys (Macaque monkeys), the Coastal taipan (0.24 mg/kg) and Many-banded krait (0.28 mg/kg) were also elevated above both the Inland taipan and Eastern brown snake in the toxicity of their venoms, ranking second and third behind the black mamba, respectively.
It is estimated that only 10 to 15 milligrams (0.15 to 0.23 gr) will kill a human adult, and its bites delivers about 120 milligrams (1.9 gr) of venom on average, although a large specimen can often deliver 200 to 300 milligrams (3.1 to 4.6 gr) in a single bite they may even deliver up to 400 milligrams (6.2 gr) of venom in a single bite. The black mamba's venom glands contain approximately 8–16 ml of liquid venom. In the freshly hatched young, the amount is 1–2 ml of venom, which is sufficient quantity for a lethal effect on a human. Black mamba bites are most commonly inflicted on the calf and up to about 10 centimetres (3.9 in) above the knee. Its bite is often called "the kiss of death" because before antivenom was widely available, the mortality rate from a bite was 100% due to the highly toxic nature of the venom and the rapidity in which a bite is fatal. The fatality duration and rate depends on various factors, such as the health, size, age, and psychological state of the victim, the penetration of one or both fangs from the snake, the amount of venom injected, the pharmacokinetics of the venom, the location of the bite, and its proximity to major blood vessels. The health of the snake and the interval since it last used its venom mechanism is important, as well. Severe black mamba envenomation can kill a person in 20 minutes, but sometimes it takes up to 6-8 hours, depending upon many factors.
If bitten, prominent neurotoxicity invariably ensues. Their venom contains neurotoxically acting nicotinic acetylcholine receptor antagonists analogical to the postsynaptic neurotoxins of other elapids classified as α, β, γ and δ neurotoxins. Mambas also carry powerful, rapid-acting and efficient pre-synaptic neurotoxins called dendrotoxins (DTX) - peptides causing inhibition by blocking voltage channeled by potassium for the re-polarization of neurons, thus causing extension of the process. This way, the substances support muscular paralysis, either at a central level or by exhausting neuromuscular junctions by super-threshold stimulation. The effect of DTX is very probably manifest on the vegetative nerves as well. The DTX I subtype of the black mamba is the most rapid-acting and efficient venoms of all known snake venom toxins. A number of peptides isolated from mamba's venom potentiate neurotransmission in the central nervous system as well as in peripheral nerves. They are limited only to the mamba's venom outfit. The peptides, acting as muscarinic acetylcholine receptor ligands, may probably cause activation in the central nervous system. Fasciculins are peptide acetylcholinesterase inhibitors increasing the intrasynaptic amount of acetylcholine, which results in fasciculation of muscles. Dendroaspin natriuretic peptide (DNP) is a polypeptide analogous to the human atrial natriuretic peptide; it is responsible for causing diuresis through natriuresis and dilating the vessel bloodstream, which results in, among other things, acceleration of venom distribution in the body of the victim. Mamba venom has powerful cardiotoxic components as well. The venom displays relatively high activity in terms of hyaluronidases, which is also essential in facilitating propagation of venom components throughout tissue.
Black mamba bites in general often result in severe, life threatening envenoming that rapidly progresses to signs of prominent neurotoxicity, particularly causing respiratory paralysis in extraordinarily rapid time (10-20 minutes) if the nature of the bite is very severe. Very urgent assessment and management is required. All cases must be admitted, as envenoming can be delayed, though this is extremely rare among cases of envenomation by this species, and can recur over several days, despite treatment, so early discharge is inappropriate. Patients should have an insertion of an IV line and be given an initial IV fluid load. Supportive respiratory therapy, including intubation and mechanical ventilation is required and is mandatory in cases of black mamba envenomation. Local symptoms of envenoming by this species is often minimal, but can be moderate to severe in very rare cases. Bleeding might occur from the bite wound. Minor redness and minor localized edema might appear around the bitten site. Pain is minimal and may last up to a week. Local tissue damage (necrosis, blistering) appears to be relatively infrequent and of minor severity in most cases of black mamba envenomation. Major swelling of the bitten limb can occur, but is uncommon. It is unclear if this can result in hypovolaemic shock secondary to fluid shifts. Bleeding might occur from the bite wound. There are no reports of compartment syndrome occurring. Systemic symptomology, even life threatening symptoms, can manifest very early on - within 10 minutes, or less. Common symptoms are rapid onset of tingling sensations, muscle twitching, dizziness, excessive sweating, headache, drowsiness, coughing or difficulty breathing, severe abdominal pain, erratic heartbeat, collapse, and convulsions. Other common symptoms which come on rapidly include neuromuscular symptoms, shock, loss of consciousness, hypotension, pallor, ataxia, urinary and fecal incontinence, excessive salivation (oral secretions may become profuse and thick), limb paralysis, nausea and vomiting, ptosis, and fever. Nephrotoxicity or renal failure has been reported in some black mamba bites in humans and in animal models. Oliguria or anuria with possible changes in urinary composition will herald the development of renal shutdown. Cardiotoxicity is common in black mamba bites in humans. Changes in cardiovascular status result primarily from the effects of circulatory collapse and shock, as well as vagal blockade resulting in tachydysrhythmias. Pulse and pressure may initially be within normal limits, but may change with rapid onset cardiovascular collapse. Myocardial infarctions (heart attacks) have also been reported in black mamba envenomation. The most important treatments are support of failing respiratory function and IV antivenom therapy using the SAIMR Polyvalent Antivenom. The initial dose will depend on severity of envenoming, but bites from this species generally require an initial dose of 10 vials. Further doses are often required. The criteria for further dosing are not well established, but if there is inadequate response by 1 hour after the initial dose, giving a repeat dose of 5-10 vials is usually required. It may take up to 30+ vials of antivenom to fully neutralize the venom. Medical staff should always have adrenaline and resuscitation equipment ready in case of adverse reactions. It is unclear if acetylcholinesterase inhibitor will be effective in a black mamba bite, with one report of useful response in a Western green mamba (Dendroaspis viridis) bite, but since a prime venom component is an effective anticholinesterase (fasciculins), the value of this therapy is most uncertain theoretically. Death is often due to suffocation resulting from paralysis of the respiratory muscles, but it may also result from a heart attack.
Clinical cases and antivenom
- Dangerousness of bite: Severe Envenoming likely (>80%), high lethality potential.
- Rate of Envenoming: >95%.
- Untreated Lethality Rate: 100%.
Envenomation by this species invariably causes prominent neurotoxicity due to the fact that black mambas possess a highly potent and rapid acting venom and often strike repeatedly in a single lunge, biting the victim many times in extremely rapid succession. Such an attack is so fast, lasting less than one second and so it appears to be a single strike and single bite. With each bite the snake delivers anywhere from 100 to 400 milligrams (1.5 to 6.2 gr) of a rapid-acting and highly toxic venom. As a result, the doses of antivenom required for successful treatment are often massive (10–20+ vials) for bites from this species. It is not unusual to use 30+ vials in extremely severe cases. In addition to antivenom therapy, endotracheal intubation and mechanical ventilation are required for supportive therapy.
A polyvalent antivenom produced by the South African Institute for Medical Research (SAIMR) is used to treat all black mamba bites from different localities. Due to antivenom, a bite from a black mamba is no longer a certain death sentence. But in order for the antivenom therapy to be successful, vigorous treatment and large doses of antivenom must be administered very rapidly post-envenomation. In case studies of black mamba envenomation, respiratory paralysis has occurred in less than 15 minutes. Due to the nature of the lethality of the venom and the associated 100% fatality rate among black mamba bites stimulated the production of a specific mamba antivenom, and in 1967 Louw reported the first successful treatment of two black mamba bites with a specific antivenom prepared by the South African Institute of Medical Research (SAIMR). This was the first time that any victim of a black mamba bite was scientifically documented to survive envenomation. Although antivenom saves many lives, mortality due to black mamba envenomation is still at 14%, even with antivenom therapy. According to scientist and herpetologist, Dr. David A. Warrell, human victims of black mamba bites seldom reach the hospital alive.
In a case of 10 envenomations in South Africa all ten received medical treatment but only five lived. One developed respiratory paralysis in ten minutes, and all other patients were showing signs of neurotoxicity upon arrival at the hospital. Symptoms initially included mild swelling at bite site, confusion, excessive sweating, urinary incontinence, fecal incontinence, loss of coordination, ptosis, erratic heartbeat, drowsiness, and breathing difficulties. Out of the 10 patients, five were fatal despite prompt hospitalization and induction of medical treatment. One patient died in just under 30 minutes. The four other patients all died within 3–8 hours post-envenomation. The other five patients survived but all of them required massive amounts of antivenom and assisted mechanical ventilation for a prolonged period. Three of the patients were on mechanical ventilation for 10 days, while the other two required assisted mechanical ventilation for 16 days. Cases of this nature are not at all uncommon among cases of envenomation by the black mamba.
Another case, which was publicized, is that of 28-year old British student named Nathan Layton. Mr. Layton was bitten by a black mamba and died of a heart attack in less than an hour after being bitten in March of 2008. Mr. Layton and his girlfriend were attending the South African Wildlife College in Hoedspriut, South Africa, training to be safari guides. The black mamba had been found near a classroom at the Southern African Wildlife College in Hoedspruit and put in a plastic box by a staff member using a catcher stick. The snake escaped and Mr. Layton helped re-collect the snake, and along an instructor, transferred the mamba into a glass jar. Mr. Layton was bitten by the snake on his index finger during the transfer into the jar, but didn't immediately realize he'd been bitten. He thought the snake had only brushed his hand. While in class, 30 minutes post-envenomation, Mr. Layton complained of blurred vision. Not long after, Mr. Layton collapsed and died of a heart attack due to black mamba envenomation, some 50-60 minutes after being bitten. He was pronounced dead at scene.
On 17 February 1986 a 14-month-old girl (weight 10.6 kilograms (23 lb)) playing indoors was bitten on the upper side of the left shin and left calf at 07h55 by a snake. The housemaid witnessed the incident and immediately sucked at the first bite, but did not notice the second bite. The snake, a 45 centimetres (18 in) black mamba (Dendroaspis polylepis) was killed, identified by a herpetologist, and brought to the clinic with the child. The child reached the clinic 15 minutes after being bitten. She was reported to have cried vigorously and vomited once on the way. On arrival at 08h00, examination found the child very pale with cold extremities and marked sweating. Her pulse rate was 96/min and she vomited for the second time shortly after arrival. There were no neurological signs. Examination of the bite sites showed a single fang mark with 1 cm of redness surrounding it on the shin; a similar bite was found on the calf but with no evidence of inflammation. The patient’s left leg was immobilised in a splint and a firm compression crepe bandage applied to the whole limb. An intravenous line was established through a scalp vein through which half-strength Darrow’s solution was given. The child’s condition deteriorated rapidly with clinical features of peripheral shutdown and severe shock. The breathing also became laboured with audible breath sounds and croupy cough. This deterioration warranted further intervention, so at 35 minutes post-envenomation, hydrocortisone 100 mg was given intravenously, followed immediately by SAIMR polyvalent antivenom 0.5 ml diluted 10-fold with 5% dextrose. There was no evidence of a hypersensitivity reaction. The child was kept on her left side and vomited twice more, her back remaining in a bent backward position for several seconds during the vomiting attacks. After an adittional 20 ml of intravenous antivenom, her condition improved, extremities became warmer, and the pulse rate dropped to 80/min. Breathing became easier. Further antivenom was given intravenously over 45 minutes. In all the patient received a total of 150 ml of dextrose saline and 70 ml of antivenom. At 1 hour 20 minutes after the bite her condition had improved dramatically, all vital signs being stable. She was then transported to Nelspruit Hospital. Her condition remained stable although she had two episodes of vomiting with blood-stained vomit. She arrived at Nelspruit Hospital at 11h45, 3 hours and 50 minutes after the bite. Her vital signs remained stable, the ECG was normal and she was allowed to eat and drink. Apart from bruising around the bite sites she remained alert and active, passed urine, was stable and had a quiet night’s sleep. She was discharged the following day, ampicillin and anti-tetanus toxoid having been given. On day 4 she developed gastro-enteritis, was re-admitted on day 8 for further observations and baseline investigations, and discharged fit 24 hours later. There have been no resulting conditions to date.
On 9 May 1986 a 34-year-old man was bitten three times on his right ring finger by a 2.25 metres (7 ft 5 in), positively identified, black mamba (D. polylepis). He reached the clinic 35 minutes after the bite. He complained of pain at the bite site, a sensation of a swollen tongue, fullness in the head, dizziness and a constricted feeling in the back of his throat. He was very restless, sweating profusely and vomited once. The blood pressure was 100/60 mm Hg, pulse rate 112/min and there was no evidence of paralysis. Three fang marks were found on the right ring finger with fairly marked local swelling. He was given a total of 70 ml of SAIMR polyvalent antivenom intravenously over 40 minutes, preceded by hydrocortisone 500 mg and promethazine 25 mg intravenously. The symptoms disappeared after 40 ml of antivenom, although the patient remained restless and hypotensive for 2 hours after the bite. The patient was admitted to the clinic and observed for the next 48 hours. All vital signs remained stable during this period. He developed swelling and itching of his right hand and forearm, however, which responded well to betamethasone and a topical antihistamine cream. The patient was given anti-tetanus toxoid 0.5 ml intramuscularly and put on ampicillin 250 mg 4 times a day for 5 days. He was discharged fit 3 days after the bite and there have been no resulting conditions.
The epidemiology of snakebite in 251 snake bitten and 3 eye envenomed patients admitted to Shongwe hospital is described for the period of 1978-1982. The mean incidence of snakebite for the period in review was 8.4/1,000 admissions and 34/100,000 population/yr, which is higher than that reported in other surveys. The Shongwe Hospital is situated in Kangwane in the Transvaal, roughly 40 kilometres (25 mi) from the southern border of the Kruger National Park and serves the Nkomasi area between the borders of Swaziland and Mozambique. The hospital and about 15 rural clinics serve a population of over 150,000, consisting mostly of rural black people, although urbanisation is in progress in certain areas. There are eight venomous species in Kangwane that can cause death - the black mamba (Dendroaspis polylepis), the snouted cobra (Naja annulifera), the forest cobra (Naja melanoleuca), and the rinkhals (Hemachatus hemachatus) which are species that produce neurotoxic venom. The other four species are the Mozambique spitting cobra (Naja mossambica) which has a mixture of neurtoxic and cytotoxic venom, the puff adder (Bitis arietans) which is a hemotoxic and cytotoxic species and two colubrids (rear-fanged) also occur in the region - the boomslang (Dispholidus typus) and Twig snake (Thelotornis capensis). The black mamba was responsible for 20 of the 251 bites (8%). There were 5 bites (2%) which occurred on the head or neck and another 5 bites which occurred on the torso, out of these 10 bites, 9 were attributed to the black mamba. Of the 251 patients envenomated, only 4 resulted in fatality - and 3 out of the 4 were due to black mamba bites. The only other fatality was attributed to a snouted cobra. Two of the mamba bitten victims died rapidly post-envenomation while still en route to the hospital, while the other one died in the hospital despite antivenom therapy, which was administered in insufficient quantities due to low supply.
A series from Triangle Hospital in Zimbabwe showed 7 cases of neurotoxic bites from elapid snakes; 1 case was positively confirmed as a black mamba bite and there was good presumptive evidence that the other bites were also due to the mamba. There are only two elapid species of snake that can cause death in the area - the black mamba (Dendroaspis polylepis) and the snouted cobra (Naja annulifera). The snouted cobra, which was apparently fairly common in former days, proved to be extremely uncommon during the author's seven years stay in the Lowveld. Black mambas are frequently encountered and are a very common species in the area. On this basis all seven reported cases are most likely to be due to the black mamba.
A 3-year old African child was bitten by a snake at dusk (6:30 pm) outside her house on the 20th of November in 1975. The mother heard a hissing sound and saw a snake several feet long and grey black in colour. The snake was presumed with good presumptive evidence that the child was bitten by a black mamba. The physicians at the hospital were almost certain that the envenomation was caused by a mamba. She put both her two children on her lap. Within a few seconds the youngest began sweating and became very weak - it was only then that she realised that the child had been bitten on the back. She put the child on her shoulders and ran to the road, and obtained a lift to the hospital. At 30 minutes post-envenomation the child arrived at the hospital, sweating profusely and unable to stand. By the 60 minute mark, the child was cold, still sweating profusely, semi-comatose, but responded inappropriately to the pain of injections. All limbs are flaccid, stertorous respiration and marked salivation that was pink in colour. The child was was given a total of 20 ml of SAIMR polyvalent antivenom, 10 ml intravenously and 10 ml intramuscularly. The child was also intravenously administered with hydrocortisone sodium succinate 100 mg. At the 120 minute mark post-envenomation, the child was still showing marked salivation and stertorous respiration. At the 130 minute mark, the child was extremely restless and all limbs were moving. An unknown dose of diazepam (Valium) was administered intravenously. At 140 minutes post-envenomation, the child goes into cardiac arrest. The child was already previously intubated, showed intermittent positive pressure respiration with oxygen. Medical staff began to perform cardiopulmonary resuscitation (CPR). At 145 minutes post-envenomation, the child is intravenously administered with sodium bicarbonate and an unknown dose of adrenaline. At 155 minutes post-envenomation, CPR was discontinued due to continued absence of a heart beat. The child died 2 hours and 20 minutes after being bitten, despite antivenom administration, intubation and other supportive therapy.
Mamba venom is made up mostly of dendrotoxins (dendrotoxin-k – "Toxin K", dendrotoxin-1 – "Toxin 1", dendrotoxin-3 – "Toxin 3", dendrotoxin-7 – "Toxin 7", among others), fasciculins, and calciseptine. Dendrotoxins exert unusual and devastating neurotoxic effects. Being a protein of low molecular weight, the venom and its constituents are able to spread extraordinarily rapidly within the bitten tissue, so black mamba venom is the most rapid-acting of all snake venoms. 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, and Toxin 1 inhibits the K+ channels at the pre and postsynaptic level in the intestinal smooth muscle. It inhibits Ca2+-sensitive K+ channels from rat skeletal muscle‚ incorporated into planar bilayers (Kd = 90 nM in 50 mM KCl), Toxin 3 inhibits M4 receptors, while Toxin 7 inhibits M1 receptors. 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 spontaneous contraction of uterine muscle and portal vein. The venom is highly specific and virulently toxic. However, black mamba venom can kill a mouse after 4.5 minutes, the shortest time among all known venomous snakes.
Black mamba venom also contains proteins, mambalgins, which in mice act as an analgesic as strong as morphine, but without most of the side-effects. Mambalgins cause much less tolerance than morphine and no respiratory distress. They act through a completely different route, acid-sensing ion channels. Laboratory tests suggest that the pain-killing effect on humans may be similar, but this had not been tested as of October 2012[update]. Researchers were puzzled about the advantage this substance could give the snakes.
Availability of treatment
Venomous snakebites are rampant in sub-Saharan Africa. Although black mambas cause only 0.5-1% of snakebites in South Africa, they produce the highest mortality rate and the species is responsible for many snake bite fatalities. Although antivenom is now widely available and bite victims can rapidly access adequate treatment in most of Africa's medium to large cities and nearby areas, some severely impoverished African nations do not always have antivenom in stock, as it is very expensive, even by Western standards. Most of those bitten by a venomous African snake species require 5 vials of antivenom as an initial dose. A single vial of antivenom can cost anywhere from USD $160–$200, and black mamba envenomation is the costliest to treat, as 10-12 vials of antivenom are often required as an initial starting dose and more than 20 vials are often required for effective treatment. As a result of the severe nature of black mamba bites and the cost of antivenom required to treat such a bite, deaths due to black mamba envenomation are very common in Swaziland and the rate of mortality is close to 100%. Other contributing factors besides the lack of antivenom are lack of mechanical ventilation equipment, proper envenomation symptom control, and drugs. Some victims will not access medical care, but rather go to a traditional healer or witch doctor. However, Swaziland does have "Antivenom Swazi", a charity whose mission is to raise enough funds to create a "bank" of antivenom for treating snakebites, but they are specifically focused on treating black mamba bite victims in Swaziland. Although bites attributed to this species are less likely compared to most African cobra species and to the puff adder, the mortality rate is significantly higher among those envenomed by black mambas. According black mamba expert and handler, Thea Litschka-Koen, black mambas only cause 10% of the total amount of bites in Swaziland, but cause more fatalities than the Mozambique spitting cobra, which causes 80% of all bites in the same country. In Zimbabwe, the black mamba and green mamba are responsible for 18% of all snake bites, but the number of deaths due to mamba envenomation is equal to the number of deaths among those bitten by cobras, who are responsible for double the amount of bites at 37%. In Tanzania, while the black mamba is second to the puff adder in causing human fatalities, the puff adder bites almost six times the number of people that the black mamba does. A survey of snakebites in South Africa from 1957 to 1963 recorded over 900 venomous snakebites, but only seven of these were confirmed black mamba bites. From the 900 bites, only 21 ended in fatalities, including all seven black mamba bites – a 100% mortality rate.
Relationship with humans
Although respected by the local populations in Africa, the black mamba still faces human persecution because of its fearsome reputation throughout its range. With the increasing amount of its territory being inhabited by humans, the black mamba often finds itself cornered with no escape. In this situation, it will stand its ground and display incredible aggressive behavior. A group of people is usually required to kill it, as it is very fast and agile, striking in all directions while a third of its body is 3–4 feet (0.91–1.2 m) above the ground. The deep fear of this snake stems not only from its reputation for aggression, speed, and venom toxicity, but from stories and legends that have been passed down from generation to generation throughout sub-Saharan Africa. One such myth sees the mamba bite its tail to make a loop, enabling it to roll down a hill. As it comes to the bottom, it straightens like an arrow and attacks at exceptional speed. Another false perception maintains that the black mamba has superior intelligence enabling it to plan an attack on humans, where it 'ambushes' a car by waiting in the road, then coils itself around the wheel to bite the driver when he reaches his destination. Popular accounts say that the snake can balance itself on the tip of its tail.
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