A
viper is a venomous
snake, belonging to the family
Viperidae[?] (consisting of roughly 150 species). A viper is characterised by its long erectile fangs[?], which are folded back when not in use. They also have triangle-shaped heads with a distinctly narrower neck. (The broad areas of the head house the venom glands.) Their eyes have irises like a cat's eye (but if you're close enough to see that, you're probably too close!) Being 0.3-3 m long, vipers feed on small animals, which are injected with venom and then dragged along until they die.