Jameson's mamba (Dendroaspis jamesoni) is a species of highly venomous snake in the family Elapidae. The species is native to equatorial Africa. A member of the mamba genus, Dendroaspis, it is slender with dull green upper parts and cream underparts and generally ranges from 1.5 to 2.2 m (4.9 to 7.2 ft) in total length. Described by Scottish naturalist Thomas Traill in 1843, it has two recognised subspecies. The nominate subspecies is found in central and western sub-Saharan Africa, and the eastern black-tailed subspecies is found eastern sub-Saharan Africa, mainly western Kenya. Predominantly arboreal, Jameson's mamba preys mainly on birds and mammals. Its venom consists of both neurotoxins and cardiotoxins. Symptoms of envenomation in humans include pain and swelling at the bite site, followed by swelling, chills, sweating, abdominal pain and vomiting, with subsequent slurred speech, difficulty breathing and paralysis. Fatalities have been recorded within three to four hours of being bitten. The venom of the eastern subspecies is around twice as potent as that of the nominate subspecies.
Taxonomy and etymology Jameson's mamba was first described as Elaps jamesoni in 1843 by Thomas Traill, a Scottish doctor, zoologist and scholar of medical jurisprudence. The specific epithet is in honour of Robert Jameson, Traill's contemporary and the Regius Professor of Natural History at the University of Edinburgh where Traill studied. In 1848, German naturalist Hermann Schlegel created the genus Dendroaspis, designating Jameson's mamba as the type species. The generic name is derived from the Ancient Greek words δένδρον (dendron, 'tree') and ἀσπίς (aspis 'asp'). The genus was misspelt as Dendraspis by French zoologist Auguste Duméril in 1856, and went generally uncorrected by subsequent authors. In 1936, Dutch herpetologist Leo Brongersma corrected the spelling to the original. In 1936, British biologist Arthur Loveridge described a new subspecies D. jamesoni kaimosae, from a specimen collected from the Kaimosi Forest in western Kenya, observing that it had fewer subcaudal scales and a black (rather than green) tail. Analysis of the components of the venom of all mambas places Jameson's mamba as sister species to the western green mamba (Dendroaspis viridis), as shown in the cladogram below.
Description Jameson's mamba is a long and slender snake with smooth scales and a tail which typically accounts for 20 to 25% of its total length. The total length (including tail) of an adult snake is approximately 1.5–2.2 m (4 ft 11 in – 7 ft 3 in). It may grow as large as 2.64 m (8 ft 8 in). The general consensus is that the sexes are of similar sizes, although fieldwork in southeastern Nigeria found that males were significantly larger than females. Adults tend to be dull green across the back, blending to pale green towards the underbelly with scales generally edged with black. The neck, throat and underparts are typically cream or yellowish in colour. Jameson's mamba has a narrow and elongated head containing small eyes and round pupils. Like the western green mamba, the neck may be flattened. The subspecies D. jamesoni kaimosae, which is found in the eastern part of the species' range, features a black tail, while central and western examples typically have a pale green or yellow tail. The thin fangs are attached to the upper jaw and have a furrow running down their anterior surface.
Scalation
The number and pattern of scales on a snake's body play a key role in the identification and differentiation at the species level. Jameson's mamba has between 15 and 17 rows of dorsal scales at midbody, 210 to 236 (Subsp.) jamesoni) or 202 to 227 ventral scales (Subsp. kaimosae), 94 to 122 (Subsp. jamesoni) or 94 to 113 (Subsp. kaimosae) divided subcaudal scales, and a divided anal scale. Its mouth is lined with 7 to 9 (usually 8) supralabial scales above and 8 to 10 (usually 9) sublabial scales below, the fourth ones located over and under the eye. Its eyes have three preocular, three postocular and one subocular scale.
Distribution and habitat
Jameson's mamba occurs mostly in Central Africa and West Africa, and in some parts of East Africa. In Central Africa it can be found from Angola northwards to the Democratic Republic of the Congo, Republic of the Congo, Central African Republic, and as far north as the Imatong Mountains of South Sudan. In West Africa it ranges from Ghana eastwards to Togo, Nigeria, Cameroon, Equatorial Guinea and Gabon. In East Africa it can be found in Uganda, Kenya, Rwanda, Burundi and Tanzania. The subspecies D. jamesoni kaimosae is endemic to East Africa and chiefly found in western Kenya, where its type locality is located, as well as in Uganda, Rwanda, and the adjacent Democratic Republic of the Congo. It is a relatively common and widespread snake, particularly across its western range. Fieldwork in Nigeria indicated the species is sedentary. Found in primary and secondary rainforests, woodland, forest-savanna and deforested areas at elevations of up to 2,200 metres (7,200 ft) high, Jameson's mamba is an adaptable species; it persists in areas where there has been extensive deforestation and human development. It is often found around buildings, town parks, farmlands and plantations. Jameson's mamba is a highly arboreal snake, more so than its close relatives the eastern green mamba and western green mamba, and significantly more so than the black mamba.
Behaviour and ecology Jameson's mamba is a highly agile snake. Like other mambas it is capable of flattening its neck in mimicry of a cobra when it feels threatened, and its body shape and length give an ability to strike at significant range. Generally not aggressive, it will typically attempt to escape if confronted.
Breeding In Nigeria males fight each other for access to females (and then breed) over the dry season of December, January and February; mating was recorded in September in the Kakamega Forest in Kenya. Jameson's mamba is oviparous; the female lays a clutch of 5–16 eggs; in Nigeria laying was recorded from April to June, and most likely soon after November in Uganda. Egg clutches have been recovered from abandoned termite colonies.
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