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How to identify and avoid poisonous snakes and lizards

Introduction – All About Snakes

Regarding snakes, you should know:

  • Their habits.
  • How to identify the dangerous kinds.
  • Precautions to take to prevent snakebites.
  • What actions to take in case of snakebite.

Nearly all snakes avoid man if possible. A few—the king cobra of Southeast Asia, the bushmaster and tropical rattlesnake of South America, and the mamba of Africa – may aggressively attack man, but even these snakes do so only occasionally. Most snakes get out of the way and are seldom seen.

How to Avoid Snakebite

Rattlesnake in the threat positionSnakes are widely distributed. They are found in all tropical, subtropical, and most temperate regions. Some species of snakes have specialized glands that contain toxic venom, and long, hollow fangs to inject their venom.  Although venomous snakes use their venom to secure food, they also use it for self-defense. Human accidents occur when you don’t see or hear the snake, when you step on them, or when you walk too close to them.

Largest Rattlesnake ever caught was over 15 feet longFollow these simple rules to reduce the chance of accidental snakebite:

  • Don’t sleep next to brush, tall grass, large boulders, or trees. They provide hiding places for snakes. Place your sleeping bag in a clearing. Use mosquito netting tucked well under the bag. This netting should provide a good barrier.
  • Don’t put your hands into dark places, such as rock crevices, heavy brush, or hollow logs, without first investigating.
  • Don’t step over a fallen tree. Step on the log and look to see if there is a snake resting on the other side.
  • Don’t walk through heavy brush or tall grass without looking down. Look where you are walking.
  • Don’t pick up any snake unless you are absolutely positive it is not venomous.
  • Don’t pick up freshly killed snakes without first severing the head. The nervous system may still be active and a dead snake can deliver venom.

Snake Groups

Snakes dangerous to man usually fall into two groups: proteroglypha and solenoglypha. Their fangs and their venom best describe these two groups.

The proteroglypha have, in front of the upper jaw and preceding the ordinary teeth, permanently erect fangs. These fangs are called fixed fangs.

The solenoglypha have erectile fangs; that is, fangs they can raise to an erect position. These fangs are called folded fangs.

Snake Venom

Snake coiled in grassThe fixed-fang snakes (proteroglypha) usually have neurotoxic venom. This venom affects the nervous system, making the victim unable to breathe.

The folded-fang snakes (solenoglypha) usually have hemotoxic venom. These venoms affect the circulatory system, destroying blood cells, damaging skin tissues, and causing internal hemorrhaging.

Remember, however, that most venomous snakes have both neurotoxic and hemotoxic venom. Usually, one type of venom in the snake is dominant and the other is weak.

Venomous vs. Nonvenomous Snakes

No single characteristic distinguishes a venomous snake from a harmless one except the presence of poison fangs and glands. Only in dead specimens can you determine the presence of these fangs and glands without danger.

Descriptions of Venomous Snakes

There are many different venomous snakes throughout the world. It is unlikely you will see many except in a zoo. This website describes only a few venomous snakes. However, you should be able to spot a venomous snake if you:

  • Learn about the two groups of snakes and the families in which they fall.
  • Examine the pictures and read the descriptions of snakes on this website.


The viperidae, or true vipers, usually have thick bodies and heads that are much wider than their necks. However, there are many different sizes, markings, and colorations.

Viperidae snake characteristics

This snake group has developed a highly sophisticated means for delivering venom. They have long, hollow fangs that perform like hypodermic needles. They deliver their venom deep into the wound.

Viper snakeThe fangs of this group of snakes are movable. These snakes fold their fangs into the roof of their mouths. When they strike, their fangs come forward, stabbing the victim. The snake controls the movement of its fangs; fang movement is not automatic. The venom is usually hemotoxic. However, there are several species that have large quantities of neurotoxic elements, thus making them even more dangerous. The vipers are responsible for many human fatalities around the world.


The crotalids, or pit vipers, may be either slender or thick-bodied. Their heads are
usually much wider than their necks. These snakes take their name from the deep pit located between the eye and the nostril. They are usually brown with dark blotches but some kinds are green.

Crotalidae snake characteristics

Rattlesnakes, copperheads, cottonmouths (Water Moccasin), and several species of dangerous snakes from Central and South America, Asia, China, and India fall into the pit viper group. The pit is a highly sensitive organ capable of picking up the slightest temperature variance. Most pit vipers are nocturnal. They hunt for food at night with the aid of these specialized pits that let them locate prey in total darkness. Rattlesnakes are the only pit vipers that possess a rattle at the tip of the tail.

India has about twelve species of these snakes. You find them in trees or on the ground in all types of terrain. The tree snakes are slender; the ground snakes are heavy-bodied. All are dangerous.

Water Moccasin or Cottonmouth snakeChina has a pit viper similar to the cottonmouth found in North America. You find it in the rocky areas of the remote mountains of South China. It reaches a length of 1.4 meters
(5 feet) but is not vicious unless irritated. You can also find a small pit viper, about 45 centimeters (18 inches) long, on the plains of eastern China. It is too small to be dangerous to a man wearing shoes.

There are about twenty-seven species of rattlesnakes in the United States and Mexico. They vary in color and may or may not have spots or blotches. Some are small but others, such as the diamondbacks, may grow to 2.5 meters (8 feet) long.

There are five kinds of rattlesnakes in Central and South America, but only the tropical rattlesnake is widely distributed. The rattle on the tip of the tail is sufficient identification for a rattlesnake.

Deadly Coral Snake - red on yellow, you're a dead fellowMost will try to escape without a fight when approached, but there is always a chance one will strike at a passerby. They do not always give a warning; they may strike first and rattle afterward or not at all.

The genus Trimeresurus is a subgroup of the crotalidae. These are Asian pit vipers. They are normally tree-loving snakes, but some live on the ground. They basically have the same characteristics of the crotalidae—slender build and very dangerous. Their bites usually are on the upper extremities—head, neck, and shoulders. Their venom is largely hemotoxic.


Elapidae is a group of highly dangerous snakes with a powerful neurotoxic venom that affects the nervous system, causing respiratory paralysis. Included in this family are coral snakes, cobras, mambas, and all the Australian venomous snakes. The coral snake is small and has caused human fatalities. The Australian death adder, tiger, taipan, and king brown snakes are among the most venomous in the world, causing many human fatalities.

Only by examining a dead snake can you positively determine if it is a cobra or a near relative. On cobras, kraits, and coral snakes, the third scale on the upper lip touches both the nostril scale and the eye. The krait also has a row of enlarged scales down its ridged back.

Elapidae snake characteristics

You can find the cobras of Africa and the Near East in almost any habitat. One kind may live in or near water, another in trees. Some are aggressive and savage. The distance a cobra can strike in a forward direction is equal to the distance its head is raised above the ground. Some cobras, however, can spit venom a distance of 3 to 3.5 meters (10 to 12 feet). This venom is harmless unless it gets into your eyes; then it may cause blindness if not washed out immediately. Poking around in holes and rock piles is dangerous because of the chance of encountering a spitting cobra.

Laticaudidae and Hydrophidae

Sea snakeA subfamily of elapidae, these snakes are specialized in that they found a better environment in the oceans. Why they are in the oceans is not clear to scientists.

Sea snakes differ in appearance from other snakes in that they have an oar-like tail to aid in swimming. Some species of sea snakes have venom several times more toxic than the cobra’s. Because of their marine environment, sea snakes seldom come in contact with humans. The exceptions are fisherman who capture these dangerous snakes in fishnets and scuba divers who swim in waters where sea snakes are found.

There are many species of sea snakes. They vary greatly in color and shape. Their scales distinguish them from eels that have no scales.

Sea snakes occur in salt water along the coasts throughout the Pacific. There are also sea snakes on the east coast of Africa and in the Persian Gulf. There are no sea snakes in the Atlantic Ocean.

There is no need to fear sea snakes. They have not been known to attack a man swimming. Fishermen occasionally get bitten by a sea snake caught in a net. The bite is dangerous.


Poisonous Boomslang snakeThe colubridae is the largest group of snakes worldwide. In this family there are species that are rear-fanged; however, most are completely harmless to man. They have a venom-producing gland and enlarged, grooved rear fangs that allow venom to flow into the wound. The inefficient venom apparatus and the specialized venom is effective on cold-blooded animals (such as frogs and lizards) but not considered a threat to human life. However, the boomslang and the twig snake of Africa have caused human deaths.


Poisonous Gila Monster lizardThere is little to fear from lizards as long as you follow the same precautions as for avoiding snakebite. There are only two poisonous lizards: the Gila monster and the Mexican beaded lizard. The venom of both these lizards is neurotoxic. The two lizards are in the same family, and both are slow-moving with a docile nature.

The Komodo dragon (Varanus komodoensis), although not poisonous, can be dangerous due to its large size and bacteria-infested mouth. These lizards can reach lengths of 3 meters (10 feet) and weigh over 115 kilograms (253 pounds).

Poisonous Snakes

Check out our animal guide for more details on poisonous snake species.

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