Western green mamba

The western green mamba was first described by the American herpetologist and physician Edward Hallowell in 1844 as Leptophis viridis, from a specimen collected in Liberia.[5] The specific name viridis is the Latin adjective "green".[6] In 1852, Hallowell described Dinophis hammondii from two specimens of western green mambas collected in Liberia, naming it for his friend Ogden Hammond of South Carolina.[7] These were later deemed by Belgian-British zoologist George Albert Boulenger to be the same species.[3]

The genus was misspelt as Dendraspis by Dumeril in 1856, and generally uncorrected by subsequent authors. In 1936, Dutch herpetologist Leo Brongersma pointed the correct spelling was Dendroaspis.[8] Analysis of the components of the venom of all mambas places the western green mamba as sister species to Jameson's mamba.[9] In addition to being called the western green mamba, this species is also commonly known as the West African green mamba,[10] and formerly Hallowell's green mamba.[11]

Analysis of the components of the venom of all mambas places the western green mamba sister to Jameson's mamba (Dendroapsis j. jamesoni and j. kaimosae), as shown in the cladogram below.[12]

The western green mamba has a long and slender body with a long tapering tail. The average length of an adult is between 1.4 metres (4.6 ft) and 2.1 metres (7 ft), with large approaching 2.4 metres (8 ft) long.[13] The long thin head has a distinct canthus above the medium-sized eyes, which have round pupils and yellowish brown irises.[14] When threatened or otherwise aroused, the western green mamba is capable of flattening its neck area into a slight hood.[15] The snake is bright green fading to yellow or orange towards the tail. Its scales have prominent black margins, giving the species a networked pattern.[16]

The western green mamba can be mistaken for similar species such as green bushsnakes of the genus Philothamnus or the boomslang (Dispholidus typus).[17]

The western green mamba is native to West Africa from Gambia and southern Senegal to Benin, including the intervening countries (from west to east) Guinea-Bissau, Guinea, Sierra Leone, Liberia, Cote d'Ivoire (Ivory Coast), Ghana, and Togo.[1] It is common in Togo, found as far north as the Alédjo Wildlife Reserve, though may theoretically be found in Sarakawa and Djamdé forests in the Kara Region.[20] Records from Nigeria are dubious,[1] and reports from the Central African Republic are more likely to be misidentification of Jameson's mamba.[21]

Western green mambas live mainly in the coastal tropical rainforest, thicket, and woodland regions of western Africa.[13] The majority of records of the western green mamba are from within the continuous forest, but the Gambia and Guinea-Bissau records are from isolated forests. The species persists in areas where the tree cover has been removed, providing that sufficient hedges and thicket remain. Found in some suitably vegetated suburbs and towns and parklands therein.[13] It is largely confined to areas where rainfall exceeds 1,500 millimetres (60 in).[22] In Togo, however, its range extends into the drier open forests of the north, the Guinean savannas of the west, and the littoral zone.[20]

Mostly diurnal, the western green mamba spends most of its time in the forest canopy, at times at considerable height, though on occasion commonly go to the ground. When it wants to sleep it seeks out tree branches that offer dense cover. It generally retreats if encountered.[24] The oldest recorded western green mamba was a captive specimen that lived 18.7 years.[25]

The species lays a clutch of 6 to 14 eggs.[24]

The western green mamba is classified as a snake of medical importance in western SubSaharan Africa by the World Health Organization,[lower-alpha 2][26] although bites from this species are rare as it is rarely encountered.[13] When bitten, symptoms rapidly begin to manifest, usually within the first 15 minutes or less. The extraordinary speed with which the venom spreads through tissue and produces rapid manifestations of life-threatening symptoms is unique to mambas. Common symptoms of a bite from a western green mamba include local pain and swelling, although uncommon, local necrosis can be moderate, ataxia, headache, drowsiness, difficulty breathing, vertigo, hypotension (low blood pressure), diarrhea, dizziness, and paralysis. Left untreated, new and more severe symptoms rapidly progress. All symptoms worsen and the victim eventually dies due to suffocation resulting from paralysis of the respiratory muscles. Bites with envenomation can be rapidly fatal, which can be possible in 30 minutes.[14][27]

Similar to the venom of most other mambas, the western green mamba's contains predominantly three-finger toxin agents. The exception is the black mamba, whose venom lacks the potent alpha-neurotoxin as well. It is thought this may reflect the species' preferred prey—small mammals for the mainly land-dwelling black mamba, versus birds for the other predominantly arboreal mambas. Unlike that of many snake species, the venom of mambas has little phospholipase A2. Overall, the venom of the western green mamba is more potent than that of the eastern green mamba, similar or slightly less potent than that of Jameson's mamba, and much less potent than that of the black mamba.[9]

The venom consists mainly of both pre-synaptic and post-synaptic neurotoxins, cardiotoxins,[27] and fasciculins. The toxicity of the venom can vary tremendously depending on various factors including diet, geographical location, age-dependent change, and other factors. The SC and IV LD₅₀ for this species is 0.79 mg/kg and 0.71 mg/kg, respectively (Christensen and Anderson (1967)).[14] One study determined the LD₅₀ of the venom administered to mice via the intraperitoneal (IP) route was 0.33 mg/kg.[28] In another test using mice that were administered the western green mamba's venom via the intraperitoneal (IP) route the LD₅₀ was 0.045 mg/kg.[29] Another experimental IV LD₅₀ toxicity of 0.5 mg/kg has been reported, with an average wet venom yield of 100 mg.[13] Like other mamba species, western green mamba venom is among the most rapid-acting venom of snakes.[30]

Media related to Dendroaspis viridis at Wikimedia Commons

• Bushdrums.com - Green Mamba Video filmed in Gabon