The southern vine snake or twig snake is a widespread snake throughout the warm eastern parts of southern Africa. It is a slender snake and very cryptically coloured in ash grey or grey-brown with lighter patches and dark markings across the body. The head is green above with a rich brown Y-shape on the crown. A brown band extends across the eye, which has a distinct horizontal key-hole shaped pupil. The upper lip is white with black speckles. Despite being widespread and abundant, it is rarely seen, relying on its fantastic camouflage to avoid detection. This snake can sit motionless for hours in a bush or tree, waiting for prey to come past.
Prey includes lizards such as agamas and chameleons as well as a variety of smaller snakes and frogs. The bright red tongue may be waved around slowly to attract the attention of passing lizards, probably confusing it for a worm, drawing them in until they are within striking range.
Being a back-fanged snake, this snake chews on the prey, applying pressure to the primitive venom glands forcing venom to trickle down the grooved fangs and into the prey. Bites to humans, usually snake catchers, are often mild, as this snake gives a quick warning bite with limited, or no venom injected – this is termed a “dry bite”.
It is a slow-acting haemotoxic venom, very similar to boomslang venom, but not as potent. Bite victims start haemorrhaging in the body, with blood moving under the skin, dripping out of the nose and internal bleeding on the organs and through the urine. There is no antivenom for this snake and bites are treated symptomatically – usually with blood transfusions or clotting management. There has never been a death in southern Africa from this snake, however bites from larger species in central Africa have killed humans. Bites are very rare as this snake is docile and avoids humans.
If harassed, this snake may massively inflate the throat region as a warning gesture. It is likely to bite out at this stage. The vine snake may be confused with young boomslang, which have similar colours in their juvenile phase. The young boomslang has a more rounded head and massive emerald-green eye.
The vine snake is active during the day, usually perched in a bush or low tree. It may also be found threaded through wire fences or gates, looking just like a vine. It is incredibly hard to detect these snakes and the best way to find them is to listen to the alarm call of birds.
Birds like bulbuls, sunbirds and white-eyes will often surround this snake and chirp excitedly, warning other birds of the snakes’ presence. It is often attacked by the grey-headed bushshrike or spookvoel, which will peck at the snake with its sharp beak, often causing severe damage to the snake.
Despite being a highly venomous snake, the vine snake is placid and can be appreciated from a few meters away in a safe manner. The camouflage is easily appreciated whilst watching this snake as your eyes struggle to identify the body from surrounding branches and twigs.
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