| Twig snake | |
|---|---|
_(6011690147).jpg) | |
| T. capensis inKruger NP, South Africa | |
Scientific classification | |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Reptilia |
| Order: | Squamata |
| Suborder: | Serpentes |
| Family: | Colubridae |
| Subfamily: | Colubrinae |
| Genus: | Thelotornis A. Smith, 1849[1] |
| Species | |
Four species, see text. | |
Thetwig snakes (genusThelotornis), also commonly known asbird snakes orvine snakes, are a genus ofrear-fangedvenomous snakes in thefamilyColubridae. The genus is native to Africa. Allspecies in the genus have a slender and elongated profile, a long tail, a narrow head and a pointed snout. The eye of all species has a horizontal pupil, shaped like a keyhole, which gives twig snakesbinocular vision. Twig snakes are greyish-brown with faint light and dark markings. When threatened, they inflate the throat to display bold black markings between thescales. Twig snake bites are potentially deadly: the venom ishemotoxic, affecting the blood clotting mechanism and causing uncontrolled bleeding and internal hemorrhaging.[2] Bites by twig snakes have caused death in humans; famous herpetologistRobert Mertens died after being bitten by his petsavanna vine snake (Thelotornis capensis). However, envenomed bites are extremely rare when not handling the snake, as the fangs can't breach the skin except in a few places like the web between the thumb and fingers.
The genusThelotornis contains fourspecies which are recognized as being valid.[3]
| Image | Scientific name | Common name | Distribution |
|---|---|---|---|
| Thelotornis capensis A. Smith, 1849 | Savanna vine snake | southern Africa. |
.jpg) | Thelotornis kirtlandii (Hallowell, 1844) | Forest vine snake | Angola, Benin, Cameroon, Central African Republic, Congo, DR Congo, Equatorial Guinea, Gabon, Ghana, Guinea, Guinea-Bissau, Ivory Coast, Kenya, Liberia, Nigeria, Sierra Leone, Somalia, Tanzania, Togo, Uganda, and Zambia. |
_(13937474977).jpg) | Thelotornis mossambicanus (Bocage, 1895) | Eastern vine snake | Eastern Africa. |
 | Thelotornis usambaricus Broadley, 2001 | Usambara vine snake | Tanzania (East Usambara Mts), Kenya (coast), Mozambique |
Nota bene: Abinomial authority in parentheses indicates that the species was originally described in a genus other thanThelotornis.
Twig snakes are among the few rear-fanged colubrids whose bite is highlyvenomous and potentially fatal.[4] The venom ishemotoxic, and although its effects are very slow, and bites are rare, noantivenom has been developed and several fatalities (such asRobert Mertens) have occurred. They prey on birds, lizards and frogs, andconceal themselves intrees, though often at a low enough level to be able to also strike at terrestrial prey, which they may swallow upwards after killing. Their cryptic coloration and apparent ability to freeze or sway gently, aschameleons do, like a twig on a tree (hence the name), makes them hard to spot. Indeed, they may be more abundant in areas than is immediately obvious.
The African twig snakes are distinctive in appearance and unlikely on that continent to be mistaken for any other snake, if indeed the observer notices them.Thelotornis is characterised by a depressed and flat head, keyhole-shaped pupils, and inT. kirtlandii, a projectingcanthus rostralis which forms a shallow loreal groove on each side of the head, which allows some binocular vision. In appearance, the head at least is unlikely to be mistaken for any other African snake. Other characteristics include a very long tail and large back fangs. The iris inT. capensis andT. kirtlandii is yellow, and presumably therefore also inT. usambaricus.
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