Twig snake

Taxobox


name = Twig Snake
regnum = Animalia
phylum = Chordata
classis = Reptilia
ordo = Squamata
subordo = Serpentes
familia = Colubridae
genus = "Thelotornis"
subdivision_ranks = Species
subdivision ="Thelotornis capensis"
Smith, 1849
"Thelotornis kirtlandii" Hallowell 1844
"Thelotornis usambaricus" Broadley, 2001

The Twig or Bird Snakes of the genus "Thelotornis" are a group of back-fanged colubrid snakes in the family Colubridae. All species have a slender and elongated profile, a long tail, narrow head and pointed snout. The eyes each species have horizontal pupils, shaped like keyholes, which gives Twig snakes binocular vision. Twig snakes are greyish-brown with faint light and dark markings. When threatened, Twig Snakes inflates their throat to display bold black markings between the scales.

The Twig Snake is one of the several back-fanged colubrids whose bite is highly venomous and potentially fatal. The Twig Snake's venom is Hemotoxic, and although the venom's effects are very slow, and bites are rare, there is no known antidote for a bite and several fatalities (such as Robert Mertens) have occurred.

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. Preying on lizards, frogs and sometimes birds, they conceal themselves in trees but often at a low enough level to be able to also strike at terrestrial prey, which they may swallow upwards after killing it. 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.

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. This allows a certain amount of binocular vision to the snake. In appearance the head at least means that it is unlikely to mistaken for any other African snake. Other characteristics include a very long tail and large back fangs. The iris in the species capensis and kirtlandii is yellow, and presumably therefore also in usambaricus.

The Twig Snakes are also notorious for another reason: among the back-fanged colubrids, they are among the most toxic, ranking alongside the Boomslang. The great Dr Robert Mertens was killed in old age by one of a pair of captive Twig Snakes he was handling, although in fairness these species are not aggressive towards humans. Nevertheless their venom and the fact that they eat relatively hard-to-provide food items makes them unsuitable