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

venom Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...

ous

snake Snakes are elongated limbless reptiles of the suborder Serpentes (). Cladistically squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales much like other members of the group. Many species of snakes have s ...

in the family

Colubridae Colubridae (, commonly known as colubrids , from , 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. C ...

. The species is native to

Sub-Saharan Africa Sub-Saharan Africa is the area and regions of the continent of Africa that lie south of the Sahara. These include Central Africa, East Africa, Southern Africa, and West Africa. Geopolitically, in addition to the list of sovereign states and ...

Etymology

Its common name means "tree snake" in

Dutch Dutch or Nederlands commonly refers to: * Something of, from, or related to the Netherlands ** Dutch people as an ethnic group () ** Dutch nationality law, history and regulations of Dutch citizenship () ** Dutch language () * In specific terms, i ...

and

Afrikaans Afrikaans is a West Germanic languages, West Germanic language spoken in South Africa, Namibia and to a lesser extent Botswana, Zambia, Zimbabwe and also Argentina where there is a group in Sarmiento, Chubut, Sarmiento that speaks the Pat ...

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

, the name is pronounced .

Taxonomy

The boomslang is a

colubrid Colubridae (, commonly known as colubrids , from , 'snake') is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. Colu ...

snake within the

subfamily In biological classification, a subfamily (Latin: ', plural ') is an auxiliary (intermediate) taxonomic rank, next below family but more inclusive than genus. Standard nomenclature rules end botanical subfamily names with "-oideae", and zo ...

Colubrinae The Colubrinae are a subfamily of snakes within the family Colubridae. It includes numerous genus, genera, and although Taxonomy (biology), taxonomic sources often disagree on the exact number, the Reptile Database lists 717 species in 92 genera ...

. It belongs to the

genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...

Dispholidus ''Dispholidus'' is a genus of snakes belonging to the family Colubridae.D. pembae'' and '' D. punctatus''. The boomslang is thought to be closely related to members of the

genera Genus (; : genera ) is a taxonomic rank above species and below family as used in the biological classification of living and fossil organisms as well as viruses. In binomial nomenclature, the genus name forms the first part of the binomial s ...

'' Thelotornis'', ''

Thrasops ''Thrasops'' is a genus of snakes in the family Colubridae. The genus is endemic to Africa.. Species *'' Thrasops flavigularis'' – yellow-throated bold-eyed tree snake *'' Thrasops jacksonii'' – black tree snake, Jackson’s black tree sna ...

'', ''

Rhamnophis ''Rhamnophis'' is a genus of arboreal venomous snakes, commonly known as dagger-tooth tree snakes or large-eyed tree snakes, in the Family (biology), family Colubridae. The genus is Endemism, endemic to equatorial sub-Saharan Africa. There are ...

'', and ''

Xyelodontophis ''Xyelodontophis'' is a genus of snake in the family Colubridae that contains the sole species ''Xyelodontophis uluguruensis''. It is commonly known as the dagger-tooth vine snake. It is found in Tanzania Tanzania, officially the United Re ...

'', 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 use of the term in English is in the discipline of anthropology. The definition is contested, in part due to conflict ...

Dispholidini. Close relationships can be shown in the

cladogram A cladogram (from Greek language, Greek ''clados'' "branch" and ''gramma'' "character") is a diagram used in cladistics to show relations among organisms. A cladogram is not, however, an Phylogenetic tree, evolutionary tree because it does not s ...

below:

Subspecies

Two

subspecies In Taxonomy (biology), biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics (Morphology (biology), morpholog ...

are recognised, including the

nominotypical subspecies In biological classification, subspecies (: subspecies) is a rank below species, used for populations that live in different areas and vary in size, shape, or other physical characteristics ( morphology), but that can successfully interbreed. ...

. * ''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 (including tail). Some exceed . The

eyes An eye is a sensory organ that allows an organism to perceive visual information. It detects light and converts it into electro-chemical impulses in neurons (neurones). It is part of an organism's visual system. In higher organisms, the ey ...

are exceptionally large, and the head has a characteristic egg-like shape. Colouration is highly variable. Males are light green with black or blue scale edges, but adult females may be brown demonstrating

sexual dimorphism Sexual dimorphism is the condition where sexes of the same species exhibit different Morphology (biology), morphological characteristics, including characteristics not directly involved in reproduction. The condition occurs in most dioecy, di ...

. Weight varies from , with an average weight of . In this species, the head is distinct from the neck and the

canthus rostralis In snakes and amphibians, the canthus, canthal ridge or ''canthus rostralis''Spawls S, Branch B. 1995. ''The Dangerous Snakes of Africa''. Ralph Curtis Books. Dubai: Oriental Press. 192 pp. . is the angle between the flat crown of the head and the ...

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, tear ...

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 In snakes, the dorsal scales are the longitudinal series of plates that encircle the body, but do not include the ventral scales. Campbell JA, Lamar WW (2004). ''The Venomous Reptiles of the Western Hemisphere''. Ithaca and London: Comstock Publis ...

, which are arranged in 19 or 21 rows, are very narrow, oblique, strongly keeled, with apical pits. The tail is long, and the

subcaudal scales In snakes, the subcaudal scales are the enlarged plates on the underside of the tail. Wright AH, Wright AA (1957). ''Handbook of Snakes of the United States and Canada''. Comstock Publishing Associates, a Division of Cornell University Press. (7t ...

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 only 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 foun ...

, from

The Gambia The Gambia, officially the Republic of The Gambia, is a country in West Africa. Geographically, The Gambia is the List of African countries by area, smallest country in continental Africa; it is surrounded by Senegal on all sides except for ...

Guinea Guinea, officially the Republic of Guinea, is a coastal country in West Africa. It borders the Atlantic Ocean to the west, Guinea-Bissau to the northwest, Senegal to the north, Mali to the northeast, Côte d'Ivoire to the southeast, and Sier ...

Senegal Senegal, officially the Republic of Senegal, is the westernmost country in West Africa, situated on the Atlantic Ocean coastline. It borders Mauritania to Mauritania–Senegal border, the north, Mali to Mali–Senegal border, the east, Guinea t ...

and most of

Western Africa West Africa, also known as Western Africa, is the westernmost region of Africa. The United Nations defines Western Africa as the 16 countries of Benin, Burkina Faso, Cape Verde, The Gambia, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Liberia, Ma ...

(including

Benin Benin, officially the Republic of Benin, is a country in West Africa. It was formerly known as Dahomey. It is bordered by Togo to the west, Nigeria to the east, Burkina Faso to the north-west, and Niger to the north-east. The majority of its po ...

Cameroon Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the R ...

Ghana Ghana, officially the Republic of Ghana, is a country in West Africa. It is situated along the Gulf of Guinea and the Atlantic Ocean to the south, and shares borders with Côte d’Ivoire to the west, Burkina Faso to the north, and Togo to t ...

Nigeria Nigeria, officially the Federal Republic of Nigeria, is a country in West Africa. It is situated between the Sahel to the north and the Gulf of Guinea in the Atlantic Ocean to the south. It covers an area of . With Demographics of Nigeria, ...

Togo Togo, officially the Togolese Republic, is a country in West Africa. It is bordered by Ghana to Ghana–Togo border, the west, Benin to Benin–Togo border, the east and Burkina Faso to Burkina Faso–Togo border, the north. It is one of the le ...

) through Central and

Eastern Africa East Africa, also known as Eastern Africa or the East of Africa, is a region at the eastern edge of the Africa, African continent, distinguished by its unique geographical, historical, and cultural landscape. Defined in varying scopes, the regi ...

(

Democratic Republic of the Congo The Democratic Republic of the Congo (DRC), also known as the DR Congo, Congo-Kinshasa, or simply the Congo (the last ambiguously also referring to the neighbouring Republic of the Congo), is a country in Central Africa. By land area, it is t ...

, western

Ethiopia Ethiopia, officially the Federal Democratic Republic of Ethiopia, is a landlocked country located in the Horn of Africa region of East Africa. It shares borders with Eritrea to the north, Djibouti to the northeast, Somalia to the east, Ken ...

Kenya Kenya, officially the Republic of Kenya, is a country located in East Africa. With an estimated population of more than 52.4 million as of mid-2024, Kenya is the 27th-most-populous country in the world and the 7th most populous in Africa. ...

South Sudan South Sudan (), officially the Republic of South Sudan, is a landlocked country in East Africa. It is bordered on the north by Sudan; on the east by Ethiopia; on the south by the Democratic Republic of the Congo, Uganda and Kenya; and on the ...

Tanzania Tanzania, officially the United Republic of Tanzania, is a country in East Africa within the African Great Lakes region. It is bordered by Uganda to the northwest; Kenya to the northeast; the Indian Ocean to the east; Mozambique and Malawi to t ...

Uganda Uganda, officially the Republic of Uganda, is a landlocked country in East Africa. It is bordered to the east by Kenya, to the north by South Sudan, to the west by the Democratic Republic of the Congo, to the south-west by Rwanda, and to the ...

). It is found across much of

Southern Africa Southern Africa is the southernmost region of Africa. No definition is agreed upon, but some groupings include the United Nations geoscheme for Africa, United Nations geoscheme, the intergovernmental Southern African Development Community, and ...

, in a wide array of habitats, with some of the species' densest populations being in

Angola Angola, officially the Republic of Angola, is a country on the west-Central Africa, central coast of Southern Africa. It is the second-largest Portuguese-speaking world, Portuguese-speaking (Lusophone) country in both total area and List of c ...

Botswana Botswana, officially the Republic of Botswana, is a landlocked country in Southern Africa. Botswana is topographically flat, with approximately 70 percent of its territory part of the Kalahari Desert. It is bordered by South Africa to the sou ...

Eswatini Eswatini, formally the Kingdom of Eswatini, also known by its former official names Swaziland and the Kingdom of Swaziland, is a landlocked country in Southern Africa. It is bordered by South Africa on all sides except the northeast, where i ...

Malawi Malawi, officially the Republic of Malawi, is a landlocked country in Southeastern Africa. It is bordered by Zambia to the west, Tanzania to the north and northeast, and Mozambique to the east, south, and southwest. Malawi spans over and ...

Mozambique Mozambique, officially the Republic of Mozambique, is a country located in Southeast Africa bordered by the Indian Ocean to the east, Tanzania to the north, Malawi and Zambia to the northwest, Zimbabwe to the west, and Eswatini and South Afr ...

Namibia Namibia, officially the Republic of Namibia, is a country on the west coast of Southern Africa. Its borders include the Atlantic Ocean to the west, Angola and Zambia to the north, Botswana to the east and South Africa to the south; in the no ...

South Africa South Africa, officially the Republic of South Africa (RSA), is the Southern Africa, southernmost country in Africa. Its Provinces of South Africa, nine provinces are bounded to the south by of coastline that stretches along the Atlantic O ...

Zambia Zambia, officially the Republic of Zambia, is a landlocked country at the crossroads of Central Africa, Central, Southern Africa, Southern and East Africa. It is typically referred to being in South-Central Africa or Southern Africa. It is bor ...

and

Zimbabwe file:Zimbabwe, relief map.jpg, upright=1.22, Zimbabwe, relief map Zimbabwe, officially the Republic of Zimbabwe, is a landlocked country in Southeast Africa, between the Zambezi and Limpopo Rivers, bordered by South Africa to the south, Bots ...

Habitat

The boomslang is an excellent climber and is highly arboreal, living mainly in forested areas. ''D. typus'' lives in

karoo The Karoo ( ; from the Afrikaans borrowing of the South Khoekhoe Khoemana (also known as !Orakobab or Korana) word is a semidesert natural region of South Africa. No exact definition of what constitutes the Karoo is available, so its extent is ...

shrubs,

savanna A savanna or savannah is a mixed woodland-grassland (i.e. grassy woodland) biome and ecosystem characterised by the trees being sufficiently widely spaced so that the canopy does not close. The open canopy allows sufficient light to reach th ...

hs, lowland forests, and in grasslands. The boomslang is not restricted to trees and can often be found on the ground hunting, feeding, or taking shelter. It will occasionally hide underground when the weather is harsh.

Reproduction

The boomslang is

oviparous Oviparous animals are animals that reproduce by depositing fertilized zygotes outside the body (i.e., by laying or spawning) in metabolically independent incubation organs known as eggs, which nurture the embryo into moving offsprings kno ...

, 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 Incubation period (also known as the latent period or latency period) is the time elapsed between exposure to a pathogenic organism, a chemical, or ionizing radiation, radiation, and when symptoms and signs are first apparent. In a typical infect ...

. Male

hatchling In oviparous biology, a hatchling is a newly hatched fish, amphibian, reptile, or bird. A group of mammals called monotremes lay eggs, and their young are hatchlings as well. Fish Fish hatchlings generally do not receive parental care, similar t ...

s are grey with blue speckles, and female hatchlings are pale brown. They attain their adult colouration 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.

Behaviour and diet

''D. typus'' is diurnal and almost exclusively

arboreal Arboreal locomotion is the locomotion of animals in trees. In habitats in which trees are present, animals have evolved to move in them. Some animals may scale trees only occasionally (scansorial), but others are exclusively arboreal. The hab ...

. It is reclusive, and moves from branch to branch when pursued by anything too large to eat. Its

diet Diet may refer to: Food * Diet (nutrition), the sum of the food consumed by an organism or group * Dieting, the deliberate selection of food to control body weight or nutrient intake ** Diet food, foods that aid in creating a diet for weight loss ...

includes

chameleon Chameleons or chamaeleons (Family (biology), family Chamaeleonidae) are a distinctive and highly specialized clade of Old World lizards with 200 species described as of June 2015. The members of this Family (biology), family are best known for ...

s and other arboreal

lizard Lizard is the common name used for all Squamata, squamate reptiles other than snakes (and to a lesser extent amphisbaenians), encompassing over 7,000 species, ranging across all continents except Antarctica, as well as most Island#Oceanic isla ...

frog A frog is any member of a diverse and largely semiaquatic group of short-bodied, tailless amphibian vertebrates composing the order (biology), order Anura (coming from the Ancient Greek , literally 'without tail'). Frog species with rough ski ...

s, and occasionally small

mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...

bird Birds are a group of warm-blooded vertebrates constituting the class (biology), class Aves (), characterised by feathers, toothless beaked jaws, the Oviparity, laying of Eggshell, hard-shelled eggs, a high Metabolism, metabolic rate, a fou ...

s, and

eggs An egg is an organic vessel in which an embryo begins to develop. Egg, EGG or eggs may also refer to: Biology * Egg cell, the female reproductive cell (gamete) in oogamous organisms Food * Eggs as food Places * Egg, Austria * Egg, Switzerland ...

from nesting birds and reptiles, all of which it swallows whole. The boomslang will also feed on other snakes, including

cannibalising Cannibalism is the act of consuming another individual of the same species as food. Cannibalism is a common ecological interaction in the animal kingdom and has been recorded in more than 1,500 species. Human cannibalism is also well documente ...

members of its own species. During cool weather, the boomslang brumates for short periods, often curling up inside the enclosed

nest A nest is a structure built for certain animals to hold Egg (biology), eggs or young. Although nests are most closely associated with birds, members of all classes of vertebrates and some invertebrates construct nests. They may be composed of ...

of a weaverbird.

Venom

The Colubridae are collectively known as "rear-fanged" (or opisthoglyphous) snakes, as their venom-injecting teeth are situated farther back in the mouth than

elapids Elapidae (, commonly known as elapids , from , variant of "sea-fish") is a family of snakes characterized by their permanently erect fangs at the front of the mouth. Most elapids are venomous, with the exception of the genus '' Emydocephalus' ...

vipers Vipers are snakes in the family Viperidae, found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, New Zealand, Ireland, and various other isolated islands. They are venomous and have long (relative to non-viper ...

, and thus require the snake to bite, hold-on, and "chew" the venom into its victim. The boomslang snake possess a highly potent and toxic venom. The boomslang is able to open its jaws up to 170° when biting, facilitating envenomation. The venom of the boomslang is primarily a

hemotoxin Haemotoxins, hemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term ''haemotoxin'' is to some degree a misnomer since toxins that damag ...

; it works via a process in which many small clots form in the blood, causing the victim's circulatory system to improperly coagulate, resulting in excessive bleeding and death. The venom has been observed to cause bleeding in tissues such as muscle and the brain (among other organs), while, at the same time, clogging

capillaries A capillary is a small blood vessel, from 5 to 10 micrometres in diameter, and is part of the microcirculation system. Capillaries are microvessels and the smallest blood vessels in the body. They are composed of only the tunica intima (the in ...

with tiny blood clots. Other signs and symptoms include headache, nausea, sleepiness, and confusion, leading to cardiac arrest and unconsciousness. Because boomslang venom is slow-acting, symptoms may not become apparent until many hours after a bite. Although the absence of symptoms provides sufficient time for procuring

antivenom Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if ...

, it can also provide victims with false reassurances, leading to underestimation of the seriousness of the bite. Snakes of any species may sometimes fail to inject venom when they bite (a so-called "dry bite" or "bluff strike", enacted in-defense), wherein, after a few hours without any noticeable effects, victims of boomslang bites may falsely believe that their attack was simply a dry or bluff strike. 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 In toxicology, the median lethal dose, LD50 (abbreviation for " lethal dose, 50%"), LC50 (lethal concentration, 50%) or LCt50 is a toxic unit that measures the lethal dose of a given substance. The value of LD50 for a substance is the dose re ...

(LD₅₀) in mice is 0.1 mg/kg (intravenously). 0.071 mg/kg (IV) has also been reported. 12.5 mg/kg (

subcutaneously The subcutaneous tissue (), also called the hypodermis, hypoderm (), subcutis, or superficial fascia, is the lowermost layer of the integumentary system in vertebrates. The types of cells found in the layer are fibroblasts, adipose cells, and m ...

) and 1.3–1.8 mg/kg (

intraperitoneal The peritoneum is the serous membrane forming the lining of the abdominal cavity or coelom in amniotes and some invertebrates, such as annelids. It covers most of the intra-abdominal (or coelomic) organs, and is composed of a layer of mesothe ...

). 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 in humans, it has been suggested that the venom's LD₅₀ is lower in humans than in mice, with only 2 to 3 mg being enough to potentially kill a healthy adult. In 1957,

herpetologist Herpetology (from Ancient Greek ἑρπετόν ''herpetón'', meaning "reptile" or "creeping animal") is a branch of zoology concerned with the study of amphibians (including frogs, salamanders, and caecilians (Gymnophiona)) and reptiles (in ...

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

envenomation Envenomation is the process by which venom is injected by the bite or sting of a venomous animal. Many kinds of animals, including mammals (e.g., the northern short-tailed shrew, ''Blarina brevicauda''), reptiles (e.g., many snakes), spiders, i ...

s 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 Circulatory system, circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used ...

s, especially if over 24-48 hours have passed without antivenom. The boomslang is a timid snake, and bites generally occur only when people attempt to handle, catch, pursue or kill the animal. When confronted and cornered, it inflates its neck and assumes an S-shaped striking pose, a key indicator of any snake species feeling threatened.

Gallery

File:MaleBoomslang.jpg, A male boomslang File:Boomslang - Western Cape.jpg, Boomslang in Western Cape, South Africa File:Common Boomslang1.jpg, Juvenile common boomslang (''Dispholidus t. typus'') File:Common Boomslang3.jpg, Brown female common boomslang (''Dispholidus t. typus'') File:Illustrations of the zoology of South Africa (6263858468).jpg, Illustration of ''D. typus'' (named as ''Bucephalus viridis'').

References

External links

Boomslang (''Dispholidus typus'')

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