Little is known about the communication and perception abilities of boomslangs. Snakes, in general, do not have well developed eyesight but are able to see movement and color. Boomslangs, however, have stereoscopic vision allowing them to have good depth perception and color vision. Because they do not have a well-developed sense of smell, they rely on sensing vibrations on the ground and flicking their tongues outside of their mouths as a means of detecting chemical scents in the air. Colubrids in general secrete a foul-smelling odor when threatened and use pheromones in attracting mates. Boomslangs are generally solitary. As a result, they rarely communicate with other animals unless they feel threatened. When threatened, they have the ability to make their bodies appear larger by widening their neck and opening their mouth. Boomslangs rarely strike except, as a means of catching prey or if they are handled in captivity. When striking does occur, however, they do not give a warning sign before attacking.
Communication Channels: visual ; chemical
Other Communication Modes: vibrations
Perception Channels: visual ; tactile ; vibrations ; chemical
Boomslangs are at no risk of becoming endangered or threatened at the present time.
US Federal List: no special status
CITES: no special status
State of Michigan List: no special status
Sex of boomslang offspring is temperature dependent. In the spring, boomslangs hatch from their eggs after an incubation time of 2 to 3 months and can quickly grow up to 1 to 1.5 m in length. Females are usually an olive-brown color while the males are usually a vibrant green color with streaks of black and blue on the edges of their scales.
Development - Life Cycle: temperature sex determination
The highly potent venom of boomslangs can cause death in humans, but they typically only strike if handled.
Negative Impacts: injures humans (bites or stings, venomous )
There are no documented positive effects of boomslangs on humans. Boomslang venom may be useful in research of the effects and treatment of haemotoxic venom.
Positive Impacts: research and education
There is little documentation on the importance of boomslangs to their environment. They are, however, important as prey for various birds, including falcons and kestrels (Falconidae) and eagles and vultures (Accipitridae).
Boomslangs are carnivorous. Their main diet consists of small arboreal lizards and frogs, including chameleons. Occasionally, they feed on small mammals, birds, the eggs of reptiles and birds, and even cannibalize other boomslangs. Most colubrids do not change their diet throughout their lives. After injecting their prey with their highly potent, haemotoxic venom, they swallow their prey whole. Boomslangs, like most other snakes, can consume large prey because of their ability to unhinge their jaws and use muscles throughout their body to move their food down their digestive tract.
Animal Foods: birds; mammals; amphibians; reptiles; eggs
Primary Diet: carnivore (Eats terrestrial vertebrates, Eats eggs)
Dispholidus typus is a terrestrial snake species that is widely distributed throughout Africa. It is indigenous to Africa and not introduced to any other regions. This species is most commonly found in the central and southern regions of the continent. They are most abundant in Swaziland, Botswana, Namibia, Mozambique, and Zimbabwe, but have been observed as far north as Nigeria and southern Chad, and have been reported as far east as eastern Guinea.
Biogeographic Regions: ethiopian (Native )
Dispholidus typus is found in a variety of ecosystem types throughout Africa. They are commonly found in karoo scrubs, arid savannas, and east African lowland forests that range in elevation from 1200 to 1400 m. Karoo scrubs are low-lying semi-desert areas unique to South Africa. They have numerous dry seasons throughout the year. The vegetation is composed of a large variety of short, low-lying trees and shrubs. A savanna consists of a variety of grasses with several species of small, single-stemmed trees. The east African lowland forest has more abundant moisture and is composed of a greater diversity and abundance of trees than karoo and savanna. Boomslangs are also found in the Eastern and Central Plateaus (1400 to 3300 m) and in grasslands (1600 to 1700 m). The plateaus are a mountainous region located just off the coastline. These grasslands have plenty of water with thick, diverse vegetation. The most likely place to find this reptile is in the moistest areas within these regions, they tend to avoid extremely dry, desert-like ecosystems. They mainly live in low-lying shrubs and short trees. They have long, slender bodies with various colors that tend to blend with the trees and shrubs within these areas. They will occasionally move to the ground for the primary purpose of hunting and soaking up the sun.
Range elevation: 1200 to 1700 m.
Average elevation: 1500 m.
Habitat Regions: tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; scrub forest
There is little known about the lifespan and longevity of boomslangs. In the wild, they avoid interaction with humans, making it difficult to observe them in their natural environment. Based on observation in captivity, it is estimated that boomslangs live approximately eight years in the wild. Their lifespan in captivity is slightly longer and the main reason for this is the absence of predation.
Average lifespan
Status: captivity: 8.7 years.
Average lifespan
Status: wild: 8 years.
Boomslangs are long, slender snakes with small, stubby, egg-shaped heads and very large eyes. The average length of an adult is 1.2 to 1.5 meters. Since these snakes are long and slender, they can move through the trees swiftly to catch prey or flee from danger. They exhibit sexual dimorphism because the female and male differ in color. The females are generally a greenish-brown color with a light shade of brown on their bellies. Males, however, are much more colorful and can exhibit a variety of colors. They can be a deep, olive-green or bright green with black outlining of their scales. The males have also been seen with a dark brown or black dorsal scales and a bright yellow or gray belly. Early in the life of boomslangs, they are grey and have bright yellow throats with black specks. It may take a couple of years for young snakes to attain their adult color. Colubrids in general have relatively large scales on their belly. Boomslangs have an average of nineteen rows of very keeled scales. They also typically have nine large scales on their head.
Dispholidus typus is classified as a member of Solenoglypha because of their ability to fold their fangs back into their mouth when unused. Dispholidus typus is considered one of the most venomous of these rear-fanged snakes. When they bite, it appears as though they are chewing because of their rear-fangs. It is possible for boomslangs to open their mouth one-hundred seventy degrees. They primarily have very potent hemotoxic venom that they inject into their victim, attacking their circulatory system. This venom stops the clotting ability of blood causing the victim to bleed to death both internally and externally. This slow-acting venom causes symptoms to start occurring in the victim several hours after contact and can be fatal if proper treatment is not given.
Range length: 1.2 to 2.0 m.
Average length: 1.5 m.
Other Physical Features: heterothermic ; venomous
Sexual Dimorphism: sexes colored or patterned differently; male more colorful
Boomslangs are preyed upon by some of the larger carnivorous birds indigenous to southern Africa, as well as by their own species. Boomslangs spend most of their time in low-lying shrubs and short trees where their long, slender bodies and varied coloration provide excellent camouflage, hiding them from predators and aiding in the capture of prey. The coloring of boomslangs helps to camouflage them in their arboreal habitats, even at a young age. It is not know whether or not boomslangs are more prone to being preyed upon at certain stages of their lives.
Known Predators:
Anti-predator Adaptations: cryptic
The mating season for male and female boomslangs has been observed in December and January. Females follow hormonal trail left behind by the male. Unlike most other snakes, boomslangs can mate in trees. They also can mate on the ground. They do not mate for life, but there is little information on how many mates a boomslang will have in its lifetime.
Mating System: polygynandrous (promiscuous)
Female boomslangs follow the scent of male hormone trails. After mating, there is a period from four to eight weeks before the female lays eggs. Eggs are usually laid in an area of decay, such as a rotting tree stump or pile of leaves. On average, eight to fourteen leathery eggs are laid and up to 27 have been observed. After the eggs have been laid, the female generally leaves the eggs alone and never returns to check on the young. The snakes hatch using a special "egg tooth" to work their way out of the shell. At birth, the length of the baby snake ranges from 29 to 38 cm. As hatchlings, boomslangs need to eat every two or three days. At this stage, their diet consists mainly of smaller reptiles. Their first skin shedding occurs when they are approximately ten days old.
Breeding interval: Boomslangs breed once yearly.
Breeding season: Eggs are laid from late spring to early summer.
Range number of offspring: 8 to 27.
Average number of offspring: 14.
Range gestation period: 4 to 8 weeks.
Average time to independence: 10 days.
Range age at sexual or reproductive maturity (female): 2 to 3 years.
Range age at sexual or reproductive maturity (male): 2 to 3 years.
Key Reproductive Features: seasonal breeding ; sexual ; oviparous
Generally, females lays the eggs in a nest of rotting vegetation to aid in incubation. Once the young hatch, they are independent.
Parental Investment: pre-fertilization (Provisioning, Protecting: Female); pre-hatching/birth (Provisioning: Female, Protecting: Female)
The boomslang (/ˈboʊmslɑːŋ/, /ˈbɔːmsləŋ/, or /ˈbuːmslæŋ/; Dispholidus typus) is a large, highly venomous snake in the family Colubridae.[2]
Its common name means "tree snake" in Dutch[3] and Afrikaans – boom meaning "tree", and slang meaning "snake". In Afrikaans, the name is pronounced [ˈbuəmslaŋ]. The boomslang is thought to be closely related to members of the genera Thelotornis, Thrasops, Rhamnophis, and Xyelodontophis, with which it forms the taxonomic tribe Dispholidini.[4]
Two subspecies are recognised, including the nominotypical subspecies.[5]
The trinomial authority in parentheses for D. t. typus indicates that the subspecies was originally described in a genus other than Dispholidus.
The average adult boomslang is 100–160 centimetres (3.3–5.2 ft) in total length. Some exceed 183 centimetres (6.00 ft). The eyes 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; this demonstrates as sexual dimorphism.[6]
Weight varies from 175 to 510 g (0.386 to 1.124 lb), with an average weight of 299.4 g (0.660 lb).[7]
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 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 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.[1]
The boomslang is endemic to sub-Saharan Africa. It is found in South Africa, Eswatini, Mozambique, Botswana, Namibia and north through sub-Sahara Africa.
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.[8]
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 colouration after several years. Hatchlings are about 20 cm (7.9 in) in length and pose no threat to humans, but are dangerously venomous by the time they reach a length around 45 cm (18 in) and a girth as thick as an adult's smallest finger.
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,[2] frogs, and occasionally small mammals, birds, and eggs from nesting birds and reptiles,[2][9] all of which it swallows whole. Boomslangs will also feed on other snakes, including cannibalising members of their own species.[10] During cool weather, boomslangs brumate for short periods, often curling up inside the enclosed nest of a weaverbird.
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.[2] The boomslang is able to open its jaws up to 170° when biting.[11] 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 haemorrhaging into tissues such as muscle and the brain while at the same time clogging capillaries with tiny blood clots.[2][12] Other signs and symptoms include headache, nausea, 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.[13]
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An adult boomslang has 1.6 to 8 mg of venom.[14] Its median lethal dose (LD50) in mice is 0.1 mg/kg (intravenously).[15] 0.071 mg/kg (IV) has also been reported.[16] 12.5 mg/kg (subcutaneously) and 1.3-1.8 mg/kg (intraperitoneal).[17] 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.[18]
In 1957, herpetologist Karl Schmidt died after being bitten by a juvenile boomslang, which he had doubted could produce a fatal dose.[19][20] He made notes on the symptoms he experienced almost to the end.[21][22] D. S. Chapman reported eight serious envenomations by boomslangs between 1919 and 1962, two of which were lethal.[23]
Boomslang monovalent antivenom was developed during the 1940s. The South African Vaccine Producers manufactures a monovalent antivenom for use in boomslang envenomations.[24] Treatment of bites may also require complete blood transfusions, 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.
A male boomslang
Boomslang in Western Cape, South Africa
Juvenile Common Boomslang (Dispholidus typus ssp. typus)
Brown female Common Boomslang (Dispholidus typus ssp. typus)
The boomslang (/ˈboʊmslɑːŋ/, /ˈbɔːmsləŋ/, or /ˈbuːmslæŋ/; Dispholidus typus) is a large, highly venomous snake in the family Colubridae.
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