IV. Family Viperidae

All species of this family are venomous. They are either terrestrial or aquatic.  The body is large, either stout or slender and generally covered with keeled scales. The head is large and triangular in shape and the eyes are distinct with vertically elliptical pupils. Large poisonous fangs are attached to moveable maxillary bones, as no maxillary teeth are present. These species are found in a variety of habitats such as rocky areas, marshy places and cultivated fields. They normally feed on frogs, toads, rodents, lizards and insects. Their venom is haemotoxic in nature. All species are aggressive, nocturnal and viviparous.

The snakes of this family are also found in all continents of the World except Antarctica. In Pakistan, 4 genera and 5 species of this family are found. These are as follows: