Eastern green mamba
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 Eastern green mamba
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| Dendroaspis angusticeps (A. Smith, 1849)[[1][2] | ||||||||||||||||||||
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The Eastern green mamba (Dendroaspis angusticeps), also known as the East African green mamba or simply just the green mamba is a species of highly venomous snake native to Africa and belonging to the Elapidae family. It is an active, arboreal snake feeding almost exclusively on birds and small mammals. It is a shy species that's rarely ever seen. It occurs on the coastal regions of east Africa from Kenya to South Africa. Like other mamba species, it is highly venomous and a single bite can easily kill more than one grown adult human.
Etymology
The eastern green mamba was described by Scottish zoologist Andrew Smith in 1849.[3] The genus name is derived from the Ancient Greek word - Dendroaspis meaning "tree asp" (dendro is "tree", while aspis is "asp" which is understood to mean a "venomous snake") and angusticeps is derived from Latin and angustus means "narrow", while -ceps means "head", calling attention to the long narrow head of this species.[4]
Description
This is a fairly large, with a slightly compressed, and very slender bodied snake with a medium to moderately long tapering tail. The eastern green mamba averages around 1.8 m (5.91 ft) in length, but may grow to lengths of 2.5 m (8.2 ft). The head is narrow and elongate, with a distinct canthus and slightly distinct from the neck. The neck may be flattened when snake is aroused, but there is no real hood. The eyes are medium in size with round pupils. Dorsal scales are oblique, smooth and narrow.[5] Adults are bright emerald green above, sometimes with a few scattered yellow scales. Below, pale green or yellowish green. Sometimes they may have a dull appearance before sloughing. Juveniles are often blue-green until they reach a length of 75 cm (29.53 in), at which stage they rapidly assume the colours of the adults. The mouth lining is bluish white, and occasionally dark.[6]
Scalation
Dorsal scales in 19 rows at midbody (sometimes 17 or 21), with 201-232 ventral scales, and 99-126 paired subcaudals. The anal shield is divided. There are 7-9 upper labials, the 4th entering the eye, and 9-11 lower labials, as well as 3 preoculars and 3-5 postoculars. Temporals are variable, usually 2+3.[6]
Distribution and habitat
Geographical distribution
This species is indigenous to the east coast of southern Africa and occurs throughout much of eastern Africa. It is found near the coast stretching from western South Africa through to Mozambique, Tanzania, Swaziland, and as far as south-east Kenya, going inland as far as southern Malawi and eastern Zimbabwe.[5][7]
Habitat
Eastern green mamba's are an arboreal species and thus are almost always found in trees. Very rarely are they found on the ground unless driven by prey or for their need to bask under the sun. They are not usually found in open terrain. Thickly forested and bush-covered areas such as evergreen lowland forests, mainly make for this species' habitat. They can also be found in regions like coastal scrub, woodland, and moist savanna where they favour bamboo and mango plantations. The species can even be found in dense montane forest up to about 1700 m (5577.43 ft) above sea level. They're often found in thickets and farm trees (citrus, cashew nut, coconut and mango) which offer plenty of shade. In coastal east Africa it is known to enter houses and often shelters in thatched roof dwellings.[5] In South Africa this snake is usually found in dense coastal vegetation. They may even be found in tropical or sub-tropical regions within their range.[6]
Behaviour and ecology
Behaviour and habits
An arboreal species that seldom ventures to the ground, except to bask or maybe for prey. It is active during the daylight hours, which makes it diurnal, and moves very gracefully and effortlessly , quickly disappearing into its leafy background. Although an active snake, it is not often seen. It is also shy, but lacks the aggression and nervousness of the black mamba and rarely gapes when threatened. It will, however, strike if provoked. Bites are uncommon, but deadly when they do occur. The eastern green mamba sleeps in trees, usually exposed in a coiled-up posture. Holes in trees are seldom used to sleep in. Like many other species, this snake basks in the morning.[6] Branch (1988) described the eastern green mamba as an active, arboreal snake feeding exclusively on birds and small mammals. Eastern green mambas are considered to by shy and elusive snakes which are rarely seen. The scarcity of observations is usually attributed to this species' cryptic colouration and arboreal lifestyle. However, low activity levels is associated with a sedentary foraging pattern might be an alternative explanation for its inconspicuousness. A 27 day observation of two adult eastern green mambas from the coastal forest of Gede/Jimba, Kenya conducted by Michael Angilletta showed that the eastern green mamba is not a typical active foraging elapid, but rather it is a "sit-and-wait" or ambush type predator (like most Viperidae). The study suggests that the eastern green mamba displays a sit and wait strategy of foraging. This evidence does not preclude active foraging by this species, as eastern green mambas have been observed systematically hunting sleeping bats. Though very quick and agile, they are characterized by very little movement, except when moving from one hunting site to another.[8]
Diet
They've been known to raid the nests of young birds.[9] This species also preys on eggs,[10] rodents, and adult birds.[11] It is possible that non-foraging movements may result in chance encounters with stationary prey, such as nest eggs, young birds, and sleeping bats, but it is likely that active foraging is necessary to feed on these prey regularly. Sit-and-wait tactics may be successful with highly mobile prey, such as rodents and adult birds.
Reproduction
The eastern green mamba is solitary, except during mating. Males find females by following a scent trail. Male eastern green mambas will compete with other males with a ritual dance or wrestling contest on the ground, in which one male tries to force the other down. These combats may last for several hours. Combat does not include biting. Courtship and mating take place in the trees, after which the female lays between 6-17 eggs (average of 10-15 eggs are usually laid).[12] The eggs are usually laid in a hollow tree among decaying vegetation. After a little over three months, the young mambas hatch and are between 35 and 45 cm (13 to 18 inches) in length and are venomous from birth. This species can live up to 15–25 years, and 14 years if kept in captivity.[13]
Venom
The eastern green mamba is a very venomous snake. The venom consists mainly of neurotoxins, cardiotoxins, calcicludine, and fasciculins. The average venom yield per bite is 80 mg according to Engelmann and Obst (1981)[14], while Minton (1974) gives it a range of 60–95 mg (dry weight).[5] The subcutaneous LD50 is around 2.3 mg/kg[15] according to Brown, 1973 and 3.0 mg/kg according to Dr. Bryan Grieg Fry of the University of Queensland.[16] Like all other mamba species, the toxicity of individual specimens within the same species and subspecies can vary greatly based on several factors including geographical region. Local swelling is variable and sometimes absent after mamba bites. However, patients bitten by the eastern green mamba develop swelling of the entire bitten limb and also show mild haemostatic disturbances (Warrell DA; MacKay et al. 1966). The rare cases of local tissue damage usually resulted from bites on the fingers or the use of a tight tourniquet.[17] This species has caused fatalities among bitten humans. The mortality rate of untreated bites is unknown but is thought to be very high.[5]
Cited references
- ↑ Dendroaspis angusticeps (TSN 700481) at Integrated Taxonomic Information System. Accessed 19 May 2012.
- ↑ Dendroaspis angusticeps (SMITH, 1849) at The Reptile Database. Accessed 19 May 2012.
- ↑ Smith, A. (1848). Illustrations of the zoology of South Africa. Reptilia. Smith, Elder, and Co., London
- ↑ Shea, Glenn. Scanlon, John. (2007). Revision of the Small Tropical Whipsnakes Previously Referred to Demansia olivacea (Gray, 1842) and Demansia torquata (Günther, 1862) (Squamata: Elapidae). Records of the Australian Museum. Vol. 59: 117–142. ISSN 0067-1975
- ↑ 5.0 5.1 5.2 5.3 5.4 Eastern green mamba: General Details at Clinical Toxinology. Accessed 19 May 2012.
- ↑ 6.0 6.1 6.2 6.3 Marais, Johan. (2004). A Complete Guide to Snakes of Southern Africa. Cape Town: Random House Struik Publishers. 98-99 pp. ISBN 978-1-8-6872-932-6.
- ↑ Spawls, Stephen. Branch, Bill. 1995. The Dangerous Snakes of Africa: Natural History, Species Directory, Venoms and Snakebite. Oriental Press, Ralph Curtis Books. 49-51 pp. ISBN 0-88359-029-8.
- ↑ Angilletta, Michael. (1994). Sedentary behaviour of Green mambas (Dendroaspis angusticeps). Herpetological Natural History. (2) 2. 105-111 pp.
- ↑ Phelps, Tony. (1989). Poisonous Snakes. London: Blandford Press. 272 pp. ISBN 0713721146
- ↑ FitzSimons, VFM. (1962). Snakes of Southern Africa. Purnell & Sons, South Africa. 423 pp. ASIN B0006CG1MS
- ↑ Ionides, CJP. (1953). Notes on Mamba (genus Dendroaspis) in the Southern Province of Tanganyika territory. African Wildlife. 7: 303-313.
- ↑ O'Shea, Mark. 2005. Venomous Snakes of the World. United Kingdom: New Holland Publishers. 79 pp. ISBN 0-691-12436-1.
- ↑ Eastern green mamba at WhoZoo. Accessed 19 May 2012.
- ↑ Engelmann, Wolf-Eberhard (1981). Snakes: Biology, Behavior, and Relationship to Man. Leipzig; English version NY, USA: Leipzig Publishing; English version published by Exeter Books (1982), 51. ISBN 0-89673-110-3.
- ↑ Brown JH (1973) Toxicology and Pharmacology of Venoms from Poisonous Snakes. Springfield, Illinois: Charles C. Thomas. 184 pp. LCCCN 73-229. ISBN 0-398-02808-7
- ↑ Fry, Bryan Grieg. LD50 Menu. Australian Venom Research Unit. University of Queensland. Retrieved on 19 May 2012.
- ↑ WHO - Guidelines for the Prevention and Clinical Management of Snakebite in Africa. WHO Regional Office for Africa. World Health Organization. Retrieved on 19 May 2012.