Poisonous snakes use venom because it is a very good way to capture prey. There is no need for a poisonous snake to spend hours and a great deal of energy squeezing its prey, and there is no need to chase after prey. The snake simply injects its venom and waits for it to take effect.

Rear-fanged snakes, such as the African boomslang, have rather small fangs. These are so far back in the mouth that the snake must get its mouth almost completely around something before the fangs can do their job. The fangs are U-shaped, and instead of injecting venom they merely channel it.

Front-fanged snakes, such as the coral snake, have fangs in a better position to deliver a dose of venom than those of rear-fanged snakes. The fangs are still rather small, but they are founded enough to inject the venom more efficiently.

Large-fanged snakes, like the rattlesnake, are able to inject venom very efficiently. The fangs fold up when the mouth is closed, but can swing into position to strike the moment the mouth is opened. Each fang is long and hollow like a hypodermic needle, so venom can be injected under pressure.

Many vipers have venom glands so large that the sides of their heads are expanded to make room for them. A heart-shaped head is a sure way to identify these poisonous snakes, since no other snakes have heads of a similar shape.

Of the 2,700 different kinds of snakes in the world, only about 400 are poisonous to some degree. Of these, fewer than 50 are really dangerous to man. The rest are either too timid to attack people or they do not inject enough venom to do much harm. Some of the snakes that are most dangerous to people are shown below.

King Cobra