Boomslang (Dispholidus typus)

Description

A long slender snake, with an average length of 1.5 meters growing to over 2.0 m in length, with a large blunt head that is distinct from the neck. It has a very large eye, which is characteristic. The body has keeled scales in 19 oblique rows at midbody. The colour is variable, with the females normally grey or brown, and the males green with black edging to the scales giving it a barred effect, or black on the dorsum with a yellow spot on each scale and a yellow belly. The juveniles are grey, with a brown head and white jaw, with the eye bright green. It is often stated that green individuals are males and brown individuals are females, but this is not always the case.

Dentition

The maxilla bone carries from 1 to 3 large grooved fangs on the back of the bone. The fangs are situated below the eye of the snake. It is also often stated that this snake can only deliver a bite on a finger because the fangs are situated in the back of the mouth, but this is not the case. A boomslang can deliver a bite to the arm, leg or shoulder. There is considerable movement in the maxilla bone so the fang can be swung forward and almost 90 degrees to the plane of the mouth, and although the fang is positioned under the eye, the mouth has a very large gap, making it relatively easy for the snake to inflict a bite. However these snakes are reluctant to bite.
Venom

The venom is haemotoxic and causes internal hemorrhage. Clotting factors II and X are attacked by the venom. This removes fibrinogen from the blood causing the blood to go thin, which then results in a bleeding syndrome. Large patches of ecchymosis will indicate bleeding under the skin. The venom is produced in minute quantities of about 1 – 15 mg. This is the most venomous of the African snakes, with an estimated lethal dose for a man is about 1mg.The venom is slow acting, with death occurring from 24 – 72 hours or even longer after a bite was inflicted. Monovalent antivenom is produced in South Africa for this snake’s bite, and is very effective, even days after the bite. Because of the slow acting venom, there would normally be enough time to get to a hospital where proper medical treatment in the form of monovalent Boomslang antivenom is the preferred form of medical treatment. The Boomslang was for many years considered a semi-venomous snake, and thought not to be capable of killing a human. However in 1956 the famous American herpetologist, Karl P. Schmidt of the Chicago Museum of Natural History received a single fang bite from a 75 cm specimen, and died 24 hours after the bite. The deadly nature of this venom was subsequently studied in South Africa and in the early 1960’s the monovalent Boomslang antivenom was developed in South Africa.

Distribution

From the Western Cape along the south coast, along the KZN coast, northwards into Mpumalanga, Gauteng, Limpopo, North West, and Northern Cape. Further north into Mozambique, Botswana, Namibia and north throughout sub-Sahara Africa.
Habitat

The name Boomslang, which is used universally, is Afrikaans for “tree snake”. So from this it can be surmised that the Boomslang is a tree living snake. They prefer savanna and open bush to coastal bush. Also found in very sparsely treed areas, like the Highveld of Gauteng, where it occurs along tree fringed streams and rivers. Although the Boomslang hunts and spends a lot of time in trees it will descend to the ground to cross open gaps between trees and will also go underground when the weather is inclement.

Habits

This snake is active during the day. It avoids human contact and rarely bites, but will demonstrate its displeasure when it is molested by inflating the front part of the body. From this position it may strike out at its aggressor. Because it hunts in trees the warnings of birds will normally alert people to the presence of the snake. The fangs are large, and the gap is considerable, allowing the snake to get its fangs into an aggressor with not too much difficulty, and although venom may not be injected in this instance, as the snake prefers to chew to get the venom into its victim’s flesh, the venom is so potent that just a scratch could cause serious symptoms. These snakes bite very rarely, and most of the recorded bites are on snake catchers. It is a fallacy that this snake can only inflict a bite on a finger, because it is back fanged. Boomslang are attracted to human habitations because of trees and water and also people keeping aviary birds, which this snake is partial to, and often gets killed because of its inability to escape through the mesh of the aviary, once a bird has been swallowed by the snake. Boomslang females produce 12 – 20 eggs during the early summer and the eggs would be laid in a tree hollow or down a rodent burrow where they would hatch about 60 days later. The babies look very different from the adults. They are grey with a very large head and emerald green eye. However they will react like an adult inflating the front part of the body when annoyed. Baby Boomslang are about 20 cm long when they hatch.