Viper, a poisonous snake. There are more than 180 species in the viper family; some are commonly called adders. Vipers have thick bodies and flat, triangular heads. Their fangs fold back against the roof of the mouth when not in use. Vipers live mainly on the ground, but some live in trees. They feed on frogs, lizards, and small mammals and birds. The females of most species bear live young. Pit vipers belong to a subfamily of the viper family.

VipersVipers are poisonous snakes with thick bodies and flat, triangular heads.

The European viper, or common adder, is found from Great Britain to southeast Asia, and within the Arctic Circle. It is pale gray to yellow with a dark brown line down its back. It grows to a length of two feet (60 cm). Its bite is rarely fatal to humans. Russell's viper, found in India, Sri Lanka, and Thailand, reaches a length of about four feet (1.2 m). It is tan, blue, and black with geometric markings on its back. Its bite is deadly. The Gaboon viper of Africa is the largest of the vipers, reaching a length of 6 1/2 feet (2 m). It is yellowish with three rows of oval, dark-ringed spots on its body. Its fangs are two inches (5 cm) long—longer than those of any other snake—and its bite is deadly.

What Are Fangs For?

Fangs are for biting, of course! Only poisonous snakes have fangs and venom glands. Fangs are hollow teeth connected to venom glands in a snake’s upper jaw. When a snake bites an animal, the venom travels through the fangs to the bite.

Vipers, which include rattlesnakes, have long, movable front fangs. Their fangs spring forward for attack. They fold back on the roof of the mouth when not in use. Most other poisonous snakes have shorter fangs that do not move.Snake venom is meant to kill an animal. Most venom has two kinds of poison. The poisons work together to damage an animal’s nerves, heart, breathing, blood vessels, and body tissues. Venom also has special enzymes (EN zymz) in it that help a snake digest an animal more quickly!

Vipers belong to the family Viperidae. The European viper is Vipera berus; Russell's viper, Daboia russelli; the Gaboon viper, Bitis gabonica.