The boomslang (, , or ; ''Dispholidus typus'') is a large, highly venomous

snake Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more ...

in the family Colubridae.

Taxonomy and etymology

Its common name means "tree snake" in

Afrikaans Afrikaans (, ) is a West Germanic language that evolved in the Dutch Cape Colony from the Dutch vernacular of Holland proper (i.e., the Hollandic dialect) used by Dutch, French, and German settlers and their enslaved people. Afrikaans gr ...

and Dutch – ''boom'' meaning "tree", and ''slang'' meaning "snake". In

, the name is pronounced . The boomslang is thought to be closely related to members of the genera '' Thelotornis'', ''

Thrasops ''Thrasops'' is a genus of snakes in the family Colubridae. The genus is endemic to Africa.. Species *'' Thrasops flavigularis'' *'' Thrasops jacksonii'' *'' Thrasops occidentalis'' *'' Thrasops schmidti'' Etymologies The generic name, ...

'', '' Rhamnophis'', and '' Xyelodontophis'', with which it forms the taxonomic

tribe The term tribe is used in many different contexts to refer to a category of human social group. The predominant worldwide usage of the term in English is in the discipline of anthropology. This definition is contested, in part due to confl ...

Dispholidini.

Subspecies

Two subspecies are recognized, including the nominotypical subspecies. * ''D. t. kivuensis'' * ''D. t. typus'' The trinomial authority in parentheses for ''D. t. typus'' indicates that the subspecies was originally described in a genus other than ''Dispholidus''.

Description

The average adult boomslang is in total length. Some exceed . The eyes are exceptionally large, and the head has a characteristic egg-like shape. Coloration is highly variable. Males are light green with black or blue scale edges, but adult females may be brown. This is known as sexual dimorphism. Weight varies from , with an average weight of . In this species, the head is distinct from the neck and the canthus rostralis is distinct. The pupil of the very large eye is round. The boomslang has excellent eyesight and often moves its head from side to side to get a better view of objects directly in front. The maxillary

teeth A tooth ( : teeth) is a hard, calcified structure found in the jaws (or mouths) of many vertebrates and used to break down food. Some animals, particularly carnivores and omnivores, also use teeth to help with capturing or wounding prey, ...

are small anteriorly, seven or eight in number, followed by three very large, grooved fangs situated below each eye. The mandibular teeth are subequal. The body is slightly compressed. The dorsal

scales Scale or scales may refer to: Mathematics * Scale (descriptive set theory), an object defined on a set of points * Scale (ratio), the ratio of a linear dimension of a model to the corresponding dimension of the original * Scale factor, a number w ...

are very narrow, oblique, strongly keeled, with apical pits, arranged in 19 or 21 rows. The tail is long, and the subcaudal scales are paired. Ventral scales are 164–201; the anal plate is divided; and the subcaudals are 91–131.

Geographic range

The boomslang is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...

sub-Saharan Africa Sub-Saharan Africa is, geographically, the area and regions of the continent of Africa that lies south of the Sahara. These include West Africa, East Africa, Central Africa, and Southern Africa. Geopolitically, in addition to the List of sov ...

. It is found in

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring coun ...

, Eswatini,

Mozambique Mozambique (), officially the Republic of Mozambique ( pt, Moçambique or , ; ny, Mozambiki; sw, Msumbiji; ts, Muzambhiki), is a country located in southeastern Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi ...

Botswana Botswana (, ), officially the Republic of Botswana ( tn, Lefatshe la Botswana, label= Setswana, ), is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory being the Kal ...

Namibia Namibia (, ), officially the Republic of Namibia, is a country in Southern Africa. Its western border is the Atlantic Ocean. It shares land borders with Zambia and Angola to the north, Botswana to the east and South Africa to the south and ea ...

and north through sub-Sahara Africa.

Habitat

The boomslang is an excellent climber and is highly arboreal, living mainly in forested areas. D. typus lives in karoo shrubs, savannahs, lowland forests, and in grasslands. Boomslangs are not restricted to trees and can often be found on the ground to hunt, feed, or take shelter. They will occasionally hide underground when the weather is harsh.

Reproduction

The boomslang is oviparous, and an adult female can produce up to 30 eggs, which are deposited in a hollow tree trunk or rotting log. The eggs have a relatively long (3 months on average) incubation period. Male hatchlings are grey with blue speckles, and female hatchlings are pale brown. They attain their adult coloration after several years. Hatchlings are about in length and pose no threat to humans, but are dangerously venomous by the time they reach a length around and a girth as thick as an adult's smallest finger.

Behavior and diet

''D. typus'' is diurnal and almost exclusively arboreal. It is reclusive, and moves from branch to branch when pursued by anything too large to eat. Its diet includes chameleons and other arboreal lizards,

frog A frog is any member of a diverse and largely Carnivore, carnivorous group of short-bodied, tailless amphibians composing the order (biology), order Anura (ανοὐρά, literally ''without tail'' in Ancient Greek). The oldest fossil "proto-f ...

s, and occasionally small

mammal Mammals () are a group of vertebrate animals constituting the class Mammalia (), characterized by the presence of mammary glands which in females produce milk for feeding (nursing) their young, a neocortex (a region of the brain), fur ...

bird Birds are a group of warm-blooded vertebrates constituting the class Aves (), characterised by feathers, toothless beaked jaws, the laying of hard-shelled eggs, a high metabolic rate, a four-chambered heart, and a strong yet lightweig ...

s, and eggs from nesting birds, all of which it swallows whole. Boomslangs will also feed on other snakes, including cannibalizing members of their own species. During cool weather, boomslangs

brumate Dormancy is a period in an organism's life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolic activity and therefore helps an organism to conserve energy. Dormancy tends to be clos ...

for short periods, often curling up inside the enclosed nest of a

weaverbird Ploceidae is a family of small passerine birds, many of which are called weavers, weaverbirds, weaver finches and bishops. These names come from the nests of intricately woven vegetation created by birds in this family. In most recent classifi ...

Venom

Many venomous members of the family Colubridae are harmless to humans because of small venom glands and inefficient fangs. However, the boomslang is a notable exception in that it has a highly potent venom, which it delivers through large fangs located in the back of the jaw. The boomslang is able to open its jaws up to 170° when biting. The venom of the boomslang is primarily a hemotoxin; it works by a process in which so many small clots form in the blood that the victim loses the ability to clot further and the victim may die as a result of internal and external bleeding. The venom has been observed to cause hemorrhaging into tissues such as muscle and the brain while at the same time clogging capillaries with tiny blood clots. Other signs and symptoms include headache,

nausea Nausea is a diffuse sensation of unease and discomfort, sometimes perceived as an urge to vomit. While not painful, it can be a debilitating symptom if prolonged and has been described as placing discomfort on the chest, abdomen, or back of th ...

, sleepiness, and mental disorders. Because boomslang venom is slow-acting, symptoms may not become apparent until many hours after the bite. Although the absence of symptoms provides sufficient time for procuring antivenom, it can also provide victims with false reassurance, leading to their underestimating the seriousness of the bite. Snakes of any species may sometimes fail to inject venom when they bite (a so-called "dry bite"), so after a few hours without any noticeable effects, victims of boomslang bites may wrongly believe that their injury is not serious or life-threatening. The pathophysiological mechanisms of the venom are different with every snake, resulting in different clinical manifestations with every patient. An adult boomslang has 1.6 to 8 mg of venom. Its median lethal dose (LD₅₀) in mice is 0.1 mg/kg (intravenously). 0.071 mg/kg (IV) has also been reported. 12.5 mg/kg ( subcutaneously) and 1.3-1.8 mg/kg ( intraperitoneal). Based on the very low venom quantities produced by ''D. typus'', and the very serious effects found in a good part of the reported cases, the lethal dosage for a man would be only 2 to 3 mg. In 1957, herpetologist Karl Schmidt died after being bitten by a juvenile boomslang, which he had doubted could produce a fatal dose. He made notes on the symptoms he experienced almost to the end. D. S. Chapman reported eight serious envenomations by boomslangs between 1919 and 1962, two of which were lethal. Boomslang monovalent antivenom was developed during the 1940s. The South African Vaccine Producers manufactures a monovalent antivenom for use in boomslang envenomations. Treatment of bites may also require complete

blood transfusion Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...

s, especially after 24 to 48 hours without antivenom. The boomslang is a timid snake, and bites generally occur only when people attempt to handle, catch, or kill the animal. When confronted and cornered, it inflates its neck and assumes an "S"-shaped striking pose.

Gallery

File:MaleBoomslang.jpg, A male boomslang File:Boomslang_-_Western_Cape.jpg, Boomslang in Western Cape, South Africa

References

External links

Boomslang (''Dispholidus typus'')

Boomslang vs.Chameleon NatGeo

Boomslang predation on Sabota Lark nest (with video)
{{Taxonbar, from=Q893048 Afrikaans words and phrases Dispholidus Reptiles described in 1828 Snakes of Africa Venomous snakes