Twig snake

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Twig snake
Vine Snake (Thelotornis capensis) (6011690147).jpg
T. capensis in Kruger NP, South Africa
Scientific classification OOjs UI icon edit-ltr.svg
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.

Contents

Species

The genus Thelotornis contains four species which are recognized as being valid. [3]

ImageScientific nameCommon nameDistribution
Vine Snake (Thelotornis capensis) (6011690147).jpg Thelotornis capensis A. Smith, 1849Savanna vine snakesouthern Africa.
NHM London Twig snake (Thelotornis kirtlandii).jpg Thelotornis kirtlandii (Hallowell, 1844)Forest vine snakeAngola, 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.
Eastern Vine Snake (Thelotornis mossambicanus) (13937474977).jpg Thelotornis mossambicanus (Bocage, 1895)Eastern vine snakeEastern Africa.
Thelotornis usambaricus.jpg Thelotornis usambaricus
Broadley, 2001
Usambara vine snakeTanzania (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.

Anatomy and behaviour

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.

Description

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.

Etymology

The specific name, kirtlandii, is in honor of American naturalist Jared Potter Kirtland. [5]

Related Research Articles

<span class="mw-page-title-main">Colubridae</span> Family of snakes

Colubridae is a family of snakes. With 249 genera, it is the largest snake family. The earliest fossil species of the family date back to the Late Eocene epoch, with earlier origins suspected. Colubrid snakes are found on every continent except Antarctica.

<span class="mw-page-title-main">Viper</span> Family of snakes

Vipers are snakes in the family Viperidae, found in most parts of the world, except for Antarctica, Australia, Hawaii, Madagascar, New Zealand, Ireland, and various other isolated islands. They are venomous and have long, hinged fangs that permit deep penetration and injection of their venom. Three subfamilies are currently recognized. They are also known as viperids. The name "viper" is derived from the Latin word vipera, -ae, also meaning viper, possibly from vivus ("living") and parere, referring to the trait viviparity common in vipers like most of the species of Boidae.

<span class="mw-page-title-main">Atractaspididae</span> Family of snakes

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.

<span class="mw-page-title-main">Snake venom</span> Highly modified saliva containing zootoxins

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 usually injected by unique fangs during a bite, though some species are also able to spit venom.

<span class="mw-page-title-main">Boomslang</span> Species of snake

The boomslang is a highly venomous snake in the family Colubridae. The species is native to Sub-Saharan Africa.

<i>Bitis nasicornis</i> Species of snake

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.

<i>Chrysopelea ornata</i> Species of snake

Chrysopelea ornata is a mildly venomous opisthoglyphous (rear-fanged) colubrid snake found in both South and Southeast Asia. It is commonly known as the golden tree snake, ornate flying snake, and golden flying snake. Along with the other species in the Chrysopelea genus, the golden tree snake is very unusual, as it is capable of a type of gliding "flight" —mainly utilised during the pursuit of prey animals—from tree-to-tree. This action is also used to great effect for the snake to flee its own potential predators. Currently, three subspecies are recognised. The snake's striking looks, and potential for gliding, have made it a coveted choice for captivity.

<span class="mw-page-title-main">Venomous snake</span> Species of the suborder Serpentes that produce venom

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 venom is typically delivered by injection using hollow or grooved fangs, although some venomous 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 venom delivered with the bite, the efficiency of the delivery mechanism, and the location of a bite on the body of the victim. Snake venom may have both neurotoxic and hemotoxic properties. There are about 600 venomous snake species in the world.

<i>Ahaetulla</i> Genus of snakes

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.

<i>Oxybelis fulgidus</i> Species of snake

(not to be confused with the Asian genus Ahaetulla, which are also referred as 'vine snakes')

<i>Rhabdophis</i> Genus of snakes

Rhabdophis is a genus of snakes in the subfamily Natricinae of the family Colubridae. Species in the genus Rhabdophis are generally called keelback snakes, and are found primarily in Southeast Asia.

<i>Rhamnophis</i> Genus of snakes

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.

<i>Telescopus</i> Genus of snakes

Telescopus, the Old World catsnakes, is a genus of 12 species of mildly venomous opisthoglyphous snakes in the family Colubridae.

<span class="mw-page-title-main">Kirtland's snake</span> Species of snake

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.

<i>Telescopus semiannulatus</i> Species of snake

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.

<i>Tachymenis</i> Genus of snakes

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.

<span class="mw-page-title-main">Cape file snake</span> Species of snake

The Cape file snake is a species of large, non-venomous snake endemic to Africa, belonging to the family Lamprophiidae.

The spotted dagger-tooth tree snake is a species of venomous snake in the family Colubridae. The species is indigenous to Middle Africa.

<span class="mw-page-title-main">Savanna vine snake</span> Species of snake

The savanna vine snake or southern vine snake is a species of venomous snake in the family Colubridae.

<span class="mw-page-title-main">Forest vine snake</span> Species of snake

The forest vine snake, also known commonly as the forest twig snake or simply the twig snake, and as the bird snake, is a species of venomous snake in the subfamily Colubrinae of the family Colubridae. The species is endemic to Africa.

References

  1. "Thelotornis ". Dahms Tierleben. www.dahmstierleben.de/systematik/Reptilien/Squamata/Serpentes/colubroidea/colubridae/colubrinae.
  2. "Twig snake". African Snakebite Institute. Retrieved 23 June 2018.
  3. Genus Thelotornis at The Reptile Database www.reptile-database.org.
  4. Goin, Coleman J.; Goin, Olive B.; Zug, George R. (1978). Introduction to Herpetology, Third Edition. San Francisco: W.H. Freeman. xi + 387 pp. ISBN   0-7167-0020-4. ("Thelotornis kirtlandi [sic]", p. 322).
  5. Beolens, Bo; Watkins, Michael; Grayson, Michael (2011). The Eponym Dictionary of Reptiles. Baltimore: Johns Hopkins University Press. xiii + 296 pp. ISBN   978-1-4214-0135-5. ("Thelotornis kirtlandi [sic]", p. 142).

Further reading