Jameson's mamba

Jameson's mamba was first described in 1843 by Thomas Traill, a physician, doctor, zoologist and scholar of medical jurisprudence.[3] In 1936, in addition to the nominotypical subspecies D. jamesoni jamesoni, Arthur Loveridge described a new subspecies D. jamesoni kaimosae; the latter is commonly referred to as the eastern Jameson's mamba or the black-tailed Jameson's mamba.[1]

The origins of the specific name, jamesoni, are not fully understood, but it is possible that Traill named the species in honour of Robert Jameson (1774–1854), who was a contemporary of Traill's and was the Regius Professor of Natural History at Edinburgh University where Traill studied.[4] Also, Traill was a member of the Wernerian Natural History Society, which was founded by Jameson.[5] The subspecies D. jamesoni kaimosae takes its subspecific name from the type locality, the Kaimosi Forest in western Kenya.[2]

Analysis of the components of the venom of all mambas places Jameson's mamba as sister species to the western green mamba.[6]

Jameson's mamba is a large, slender elapid snake with smooth scales and a long tapering tail which typically accounts for 20 to 25% of its total length.[7] The average total length (including tail) of an adult snake is approximately 1.5 meters (4.9 ft) to 2.2 meters (7.2 ft). It may grow as large as 2.64 meters (8 ft 8 in).[7] Adults tend to be dull green across the back, blending to pale green towards the underbelly with scales generally edged with black.[8] The ventral side, neck and throat are typically cream or yellowish in colour.[7] Jameson's mamba has a narrow and elongated head containing a small eye and round pupil.[7] Like the western green mamba, the neck may be flattened. The subspecies D. jamesoni kaimosae, which is typically 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.[7] No significant sexual dimorphism has been observed between male and female snakes.[9]

Jameson's mamba occurs mostly in Central Africa and West Africa, and in some parts of East Africa.[2] In Central Africa it can be found from Angola northwards to the Democratic Republic of Congo, Republic of Congo, Central African Republic, and as far north as the Imatong Mountains of South Sudan.[7] In West Africa it ranges from Ghana eastwards to Togo, Nigeria, Cameroon, Equatorial Guinea and Gabon.[2] In East Africa it can be found in Uganda, Kenya, Rwanda, Burundi and Tanzania.[7] 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 adjacent Democratic Republic of Congo.[2] It is a relatively common and widespread snake, particularly across its western range.[9]

Found in primary and secondary rainforests, woodland, forest-savanna and deforested areas at elevations up to 2,200 metres (7,200 ft) high,[7] Jameson's mamba is an adaptable species, found in areas where there has been extensive deforestation and human development. It is often found around buildings, town parks, farmlands and plantations.[7] 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.[9]

Jameson's mamba is a highly agile and almost exclusively arboreal 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. It is not typically aggressive in nature and will almost always attempt to escape.[7][9]

Like other mambas, the venom of the Jameson's mamba is a highly neurotoxic venom. Its other components include cardiotoxins,[13] and fasciculins.[8] Its venom may also have hemotoxic and myotoxic components to it.[14] The average venom yield per bite for this species is 80 mg, but some specimens may yield as much as 120 mg in a single bite. The SC LD₅₀ for this species according to Brown (1973) is 1.0 mg/kg, while the IV LD₅₀ is 0.8 mg/kg.[15] Untreated envenomation may cause death within 30 to 120 minutes.[16] However, the average death time for untreated bite victims is usually two to three hours post-envenomation, but it may take up to four to six hours or longer.[11] The mortality rate of untreated bites is not exactly known, but it is said to be very high.[8]