The western green mamba (Dendroaspis viridis) is a long, thin, and highly venomous snake species of the mamba genus, Dendroaspis. This species was first described in 1844 by American herpetologist Edward Hallowell. The western green mamba is a fairly large and predominantly arboreal species, capable of navigating through trees swiftly and gracefully. It will also descend to ground level to pursue prey such as rodents and other small mammals.
The western green mamba is a shy and agile snake that lives mainly in the coastal tropical rainforest, thicket, and woodland regions of western Africa. Its venom is a highly potent mixture of rapid-acting presynaptic and postsynaptic neurotoxins (dendrotoxins), cardiotoxins and fasciculins. Some consider this species not to be a particularly aggressive snake, but others have suggested that they are extremely nervous and are prone to attack aggressively when cornered. Conflict with humans is low compared to some other species found in the region. Bites to people by this species are quite uncommon. Their mortality rate, however, is high; many of the recorded bites have been fatal. Rapid progression of severe, life-threatening symptoms are hallmarks of mamba bites. Bites with envenomation can be rapidly fatal.
Taxonomy
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. The specific name viridis is the Latin adjective "green". 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. These were later deemed by Belgian-British zoologist George Albert Boulenger to be the same species.
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. Analysis of the components of the venom of all mambas places the western green mamba as sister species to Jameson's mamba. In addition to being called the western green mamba, this species is also commonly known as the West African green mamba, and formerly Hallowell's green mamba.
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.
Description
The western green mamba has a long and slender body with a long tapering tail. The average length of an adult is between and , with large approaching long. The long thin head has a distinct canthus above the medium-sized eyes, which have round pupils and yellowish brown irises. When threatened or otherwise aroused, the western green mamba is capable of flattening its neck area into a slight hood. 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.
The western green mamba can be mistaken for similar species such as green bushsnakes of the genus Philothamnus or the boomslang (Dispholidus typus).
Scalation
The number and pattern of scales on a snake's body are a key element of identification to species level. The western green mamba has 13 rows of long and thin dorsal scales at midbody, fewer than any similar species. Each is double the length of the ventral scales. There are 211 to 225 ventral scales, 105 to 128 divided subcaudal scales, and a divided anal scale. Its mouth is lined with 7 to 9 supralabial scales above, the fourth and sometimes fifth one located under the eye, and 9–10 sublabial scales below.
Distribution and habitat
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. 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. Records from Nigeria are dubious, and reports from the Central African Republic are more likely to be misidentification of Jameson's mamba.