The boomslang (Dispholidus typus) is a large, highly venomous snake in the family Colubridae. It is native to Africa and its common name means "tree snake" in Afrikaans.
Boomslangs have exceptionally large eyes, and their head has a characteristic egg-like shape. These snakes have excellent eyesight and often move their head from side to side to get a better view of objects directly in front. The coloration of their skin is very variable. Males are light green with black or blue scale edges, but adult females may be brown or grey in color.
Boomslangs are native to sub-Saharan Africa. They live in karoo shrubs, savannahs, lowland forests, the Eastern and Central African Plateaus, and in grasslands.
Boomslangs are diurnal and almost exclusively arboreal. They will sometimes come down to the ground for hunting and basking the sun. They may also hide underground when the weather is harsh. Boomslangs are solitary reclusive creatures and flee from anything too large to eat. They spend the day hunting in trees or shrubs, moving through tree branches until they find an ideal hiding place. These snakes are able to stalk prey without being detected. During cool weather, they brumate for moderate periods, often curling up inside the enclosed bird nests. Boomslangs are timid snakes and bite generally only when people attempt to handle, catch, or kill them. When confronted and cornered, they inflate their neck and assume an "S"-shaped striking pose.
The boomslang has a highly potent venom, which it delivers through large fangs located in the back of the jaw. It is able to open its jaws up to 170° when biting. The venom of the boomslang is primarily a hemotoxin; it disables the coagulation process 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. 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. 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 transfusions, especially after 24 to 48 hours without antivenom.
Boomslangs are carnivores. Their diet includes chameleons and other arboreal lizards, frogs, and occasionally small mammals, birds, and eggs from nesting birds.
Boomslangs are polygynandrous (promiscuous) meaning that both males and females have multiple partners. They breed in December and January. Boomslangs are oviparous, and an adult female can produce up to 30 eggs, which are deposited in a hollow tree trunk or rotting log. After the eggs have been laid, the female leaves and never returns. The eggs have a relatively long (3 months on average) incubation period. The snakelets use a special "egg tooth" to make their way out of the shell. Male hatchlings are grey in color with blue speckles, and female hatchlings are pale brown. They attain their adult coloration after several years. Hatchlings are about 20 cm (7.9 in) in length and pose no threat to humans; they become dangerously venomous by the time they reach a length of around 45 cm (18 in).
There are no major threats facing boomslangs at present.
According to IUCN Red List, the boomslang is locally common throughout its range but no overall population estimate is available. Currently, this species is classified as Least Concern (LC) on the IUCN Red List and its numbers today are stable.
These snakes are important for the ecosystem they live in by controlling the populations of frogs, lizards, birds, and small mammals they prey on.
