Viper is any of a large group of venomous snakes that have a pair of long, hollow fangs in the upper jaw. Venomous snakes can use their fangs to inject a poisonous substance called venom into prey or attackers. Many vipers possess a deep hollow in the side of the head, a little lower than the eye and in front of it. Snakes with this hollow, or pit, are called pit vipers. Those without the pit are divided into several groups, the largest and most important of which is known as true vipers.
True vipers live in Africa, Europe, and Asia. Pit vipers live in the Americas, Asia, and Europe. Of the hundreds of species (kinds) of vipers, more than half have pits. Most vipers live in dry places, including deserts.
Vipers have a head much broader than the neck, and eyes with catlike pupils. Many other snakes, however, also possess these features, and vipers cannot be recognized clearly by the shape of the head and pupils. A majority of vipers have thick bodies and rather short tails.
A viper’s venom forms in special glands. The hollow fangs inject the venom into an animal’s body the way a hypodermic needle injects liquid. Vipers use their venom to kill prey and to defend themselves. All vipers can be dangerous to people. However, many smaller vipers rarely, if ever, kill anyone with their bite. Many kinds of large vipers are so harmless that they will not bite unless someone teases or annoys them.
A pit viper’s facial pit is a sense organ that is highly sensitive to heat. It helps the pit viper to locate its warm-blooded prey. Vipers eat mostly small mammals, but they also will feed on small birds and lizards. After biting their prey and injecting venom, vipers let the prey go and track it down later to eat it.
Familiar North and South American pit vipers include rattlesnakes and bushmasters, and the water moccasin, copperhead, and fer-de-lance. Bushmasters and the fer-de-lance live only in tropical climates. All these snakes bear their young alive except the bushmasters, which lay eggs.
The common viper, or adder, is the only venomous reptile of the United Kingdom. Other familiar true vipers include the Gaboon viper and puff adder of Africa, and Russell’s viper of southern and southeastern Asia. Most true vipers bear their young alive.
