Twig snake | |
---|---|
![]() | |
T. capensis in Kruger NP, South Africa | |
Scientific classification ![]() | |
Domain: | Eukaryota |
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. |
The twig snakes (genus Thelotornis), also commonly known as bird snakes or vine snakes, are a genus of rear-fanged venomous snakes in the family Colubridae. The genus is native to Africa. All species 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 snakes binocular vision. Twig snakes are greyish-brown with faint light and dark markings. When threatened, they inflate the throat to display bold black markings between the scales. Twig snake bites are potentially deadly: the venom is hemotoxic, affecting the blood clotting mechanism and causing uncontrolled bleeding and internal hemorrhaging. [2] Bites by twig snakes have caused death in humans; famous herpetologist Robert Mertens died after being bitten by his pet savanna 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 genus Thelotornis contains four species which are recognized as being valid. [3]
Image | Scientific name | Common name | Distribution |
---|---|---|---|
![]() | Thelotornis capensis A. Smith, 1849 | Savanna vine snake | southern Africa. |
![]() | 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. |
![]() | 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 : A binomial authority in parentheses indicates that the species was originally described in a genus other than Thelotornis.
Twig snakes are among the few rear-fanged colubrids whose bite is highly venomous and potentially fatal. [4] The venom is hemotoxic, and although its effects are very slow, and bites are rare, no antivenom has been developed and several fatalities (such as Robert Mertens) have occurred. They prey on birds, lizards and frogs, and conceal themselves in trees, 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, as chameleons 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 in T. kirtlandii, a projecting canthus 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 in T. capensis and T. kirtlandii is yellow, and presumably therefore also in T. usambaricus.
The specific name, kirtlandii, is in honor of American naturalist Jared Potter Kirtland. [5]
Hemotoxins, haemotoxins or hematotoxins are toxins that destroy red blood cells, disrupt blood clotting, and/or cause organ degeneration and generalized tissue damage. The term hemotoxin is to some degree a misnomer since toxins that damage the blood also damage other tissues. Injury from a hemotoxic agent is often very painful and can cause permanent damage and in severe cases death. Loss of an affected limb is possible even with prompt treatment.
The Atractaspididae (atractaspidids) are a family of venomous snakes found in Africa and the Middle East, commonly called mole vipers, stiletto snakes, or burrowing asps. Currently, 12 genera are recognized.
Snake venom is a highly toxic saliva containing zootoxins that facilitates in the immobilization and digestion of prey. This also provides defense against threats. Snake venom is injected by unique fangs during a bite, whereas some species are also able to spit venom.
The boomslang is a large, highly venomous snake in the family Colubridae.
Clelia is a genus of snakes, one of three genera with species with the common name mussurana or musurana It is a genus of large snakes in the family Colubridae. The genus is endemic to Central America and South America, and species of Clelia are found from southern Mexico to Brazil. They specialize in ophiophagy, i.e., they attack and eat other snakes. Currently seven species are recognized as being valid. They have other popular names in various countries, such as zopilota in Central America and cribo on some Caribbean islands.
Bitis nasicornis is a viper species belonging to the genus Bitis, part of a subfamily known as "puff-adders", found in the forests of West and Central Africa. This large viper is known for its striking coloration and prominent nasal "horns". No subspecies are currently recognized. Its common names include butterfly viper, rhinoceros viper, river jack and many more. Like all other vipers, it is venomous.
Venomous snakes are species of the suborder Serpentes that are capable of producing venom, which they use for killing prey, for defense, and to assist with digestion of their prey. The poison is typically delivered by injection using hollow or grooved fangs, although some poisonous snakes lack well-developed fangs. Common venomous snakes include the families Elapidae, Viperidae, Atractaspididae, and some of the Colubridae. The toxicity of venom is mainly indicated by murine LD50, while multiple factors are considered to judge the potential danger to humans. Other important factors for risk assessment include the likelihood that a snake will bite, the quantity of poison delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake poison may have both neurotoxic and hemotoxic or cytotoxic properties. There are about 600 venomous snake species in the world.
Ahaetulla, commonly referred to as Asian vine snakes or Asian whip snakes, is a genus of colubrid snakes distributed throughout tropical Asia. They are considered by some scientists to be mildly venomous and are what is commonly termed as 'rear-fanged' or more appropriately, opisthoglyphous, meaning their enlarged teeth or fangs, intended to aid in venom delivery, are located in the back of the upper jaw, instead of in the front as they are in vipers or cobras. As colubrids, Ahaetulla do not possess a true venom gland or a sophisticated venom delivery system. The Duvernoy's gland of this genus, homologous to the venom gland of true venomous snakes, produces a secretion which, though not well studied, is considered not to be medically significant to humans.
Oxybelis fulgidus, commonly known as the green vine snake or the flatbread snake, is a species of long, slender, arboreal colubrid snake, which is endemic to Central America and northern South America.
Rhamnophis is a genus of arboreal venomous snakes, commonly known as dagger-tooth tree snakes or large-eyed tree snakes, in the family Colubridae. The genus is endemic to equatorial sub-Saharan Africa. There are two recognized species.
Telescopus, the Old World catsnakes, is a genus of 12 species of mildly venomous opisthoglyphous snakes in the family Colubridae.
Kirtland's snake is a threatened or endangered North American species of nonvenomous snake of the subfamily Natricinae, of the family Colubridae. It is the only species in the genus Clonophis.
Telescopus semiannulatus, commonly known as the common tiger snake, tiger cat snake, western tiger snake, or eastern tiger snake is a species of rear-fanged colubrid snake. It is widespread in central, eastern, and southern Africa.
Tachymenis is a genus of venomous snakes belonging to the family Colubridae. Species in the genus Tachymenis are commonly known as slender snakes or short-tailed snakes and are primarily found in southern South America. Tachymenis are rear-fanged (opisthoglyphous) and are capable of producing a medically significant bite, with at least one species, T. peruviana, responsible for human fatalities.
The Cape file snake is a species of large, non-venomous snake endemic to Africa, belonging to the family Lamprophiidae.
The large-eyed green tree snake, also known commonly as the splendid dagger-tooth tree snake, is a species of venomous snake in the family Colubridae. The species is endemic to Africa. There are three recognized subspecies.
The spotted dagger-tooth tree snake is a species of venomous snake in the family Colubridae. The species is indigenous to Middle Africa.
The savanna vine snake is a species of venomous snake in the family Colubridae.
The forest vine snake, also known commonly as the twig snake and the bird snake, is a species of venomous snake in the family Colubridae. The species is endemic to Africa.
The eastern vine snake, also known commonly as the eastern twig snake, is a species of venomous snake in the family Colubridae. The species is endemic to Eastern Africa