Snakes: A Comprehensive Guide to Reptiles

Snake

Introduction to Snake

Snake, a limbless reptile. There are about 2,500 species of snakes. Some inhabit the sea and others live in freshwater, but the majority live on land. Land snakes may burrow in the ground or live in trees or in rocky crevices. In size, snakes range from the 4-inch (10-cm) blind snake to the reticulated python, which may be 30 feet (9 m) or longer. Snakes are often beneficial to humans by killing unwanted insects and rodents. Snake-skins are used to make shoes, handbags, and other articles. Almost all snakes bite to defend themselves or to obtain food, but only a few are venomous (poisonous). The bite of some of the venomous species can be fatal to humans.

Snakes are limbless reptiles that come in various forms.Where in the World Do Snakes Live?

Snakes live almost everywhere. You might see one while crossing a desert, climbing a mountain, or hiking in a forest. You might even see one while swimming in a lake, a river, or an ocean.

Even if you don’t see snakes, they probably live near you. Snakes can live anyplace where the ground isn’t frozen all year. They live on every continent, except Antarctica. A few islands—such as Ireland, Iceland, and New Zealand—are also snake-free.

Many snakes live on the ground. Others burrow under the ground. Some snakes like the high life and live in the trees. Still others like to stay wet and spend most of their lives in the water.

Are Snakes Deadly or Harmless?

There are more than 400 species of poisonous snakes. But most of the world’s snakes, almost 85 percent of the species, are harmless to people. Australia is the only continent where you will find more poisonous than nonpoisonous snakes.

Most poisonous snakes belong to either of two families of snakes: elapids (EHL uh pihdz) and vipers (VY puhrz). Elapids generally have short fangs. When elapids bite, they usually hang onto their prey. This gives their poisonous venom (VEHN uhm) more of a chance to enter the victim’s body. Vipers strike quickly. Their long fangs deliver their venom deeply and quickly into their prey. The rattlesnake is a viper.

What Good Are Snakes?

Snakes do plenty of good things, especially for farmers. Snakes eat mice, rats, gophers, and other small mammals that eat farm crops.

Snakes also help scientists and doctors. Snake venom is used in research and in making medicines. One medicine made from venom helps treat certain types of heart attacks. Another is antivenin (an tee VEHN uhn), a drug used to treat snakebites.

To collect snake venom, skilled workers must “milk” a poisonous snake. To milk a snake, a worker places a cup under the upper jaw of the snake’s open mouth. The worker then rubs the snake’s venom gland, and the snake shoots venom from its fangs into the cup.

Who’s Who in the Snake World?

The world is home to some pretty amazing snakes. There are blind snakes that burrow underground and may be mistaken for worms. There are sea snakes that gracefully swim through the water.

Snakes also come in an amazing range of sizes. There are tiny Brahminy (BRAH muh nee) blind snakes, which are only 6 inches (15 centimeters) long. And there are giant anacondas, which reach more than 30 feet (9 meters).

Some snakes even seem to fly. Flying snakes shoot out from tree limbs. They flatten their bodies to slow their fall.

What Does a Snake’s Coloring Mean?

Bright colors—like the red, black, and yellow or white bands of a coral snake—mean danger. They warn animals that may try to eat the coral snake that this snake’s bite is poisonous.

Some harmless snakes, such as scarlet kingsnakes and some milk snakes, mimic or copy the coloring of coral snakes. Their bright colors make them look dangerous to animals that prey on the snakes. A closer look, however, shows that the colored bands on these snakes appear in a different order.

Some snakes use their coloring as camouflage (KAM uh flahzh) to blend in with their surroundings. The green vine snake and other tree snakes loop themselves around tree branches. Hidden among the leaves, they look like vines. Their prey may not notice them—until it is too late.

Interesting facts about snakesOne of the smallest snakes is the Braminy blind snake, which lives in the tropics and grows only 6 inches (15 centimeters) long. It has tiny eyes that are covered by head scales.An African Gaboon viper in a zoo once fasted for 2 1/2 years. Snakes in zoos sometimes do not eat for 6 months to 3 years.The fastest snake is probably the black mamba of Africa. It was timed moving at the speed of 7 miles (11 kilometers) per hour over a short distance.The African ball python protects itself from enemies by coiling into a ball with its head in the middle. Many other snakes also use this method of defense.Green tree pythons may be yellow or brown when hatched. Snakes of both colors may hatch from the same batch of eggs. They turn green as they grow older. Green tree pythons live in New Guinea.The spitting cobra of Africa can squirt venom 6 to 8 feet (1.8 to 2.4 meters). The snake aims for the eyes of its enemy. The venom causes a painful, burning sensation and can produce blindness.

Structure and Habits

Snakes are cold-blooded animals, and are found chiefly in the tropics and in temperate regions. There are none in New Zealand, Ireland, or where the subsoil is always frozen. Snakes hibernate during the winter in cold countries, and may also be inactive during very hot summers.

The copperhead is a pit viper related to the rattlesnake.What Do Snakes Do in the Winter?

Many snakes, such as rattlers and garter snakes, may hibernate, or sleep, during the winter. Why do they do this? In many parts of the world, winter is too cold for snakes. They need warmer temperatures to help them keep their bodies working.

As winter approaches, snakes crawl into caves or holes in the ground to escape the cold. Often, many snakes will crowd into a single den to keep warm. Sometimes, more than one species of snake will share a den and sleep through the winter together.

While snakes hibernate, their body temperatures drop, and they stay fairly still. Hibernating snakes use up very little energy and do not have to worry about eating food. When spring arrives, they come out of their dens to warm up and to eat.

Snakes generally have compact heads that taper into their slender bodies. The head varies in shape among the different species. A pit viper, such as the rattlesnake of the United States, has a hollow, or pit, between eye and nostril. The pits are so sensitive to heat that they enable the snake to detect and strike a warm-blooded animal at some distance. The lower jaw of a snake is attached to the skull by elastic ligaments, permitting the snake to open its mouth wide enough to swallow whole animals much thicker than its own head. The elasticity of its skin also helps the snake to swallow large animals.

Snakes appear to have a fixed stare because their eyes have no lids; instead, the eyes are covered by a transparent protective membrane. The sense of smell is sharp. Snakes have no external ear or any eardrum, but the inner ear is well developed. They can hear only low-frequency sounds in the air, but can feel the vibrations that sound waves create in the ground.

All snakes have forked tongues. The tongue plays a role in the snake's sense of smell; in effect, it transmits odor to an organ of smell inside the mouth. For this reason, the tongue constantly flicks in and out, seeking the scent of prey. A snake's teeth are used for grasping prey rather than for chewing. They are sharp, cone-shaped structures that curve backward toward the throat. Venomous snakes, in addition, have two needle-sharp fangs, grooved or tubular so they can conduct a fluid from poison-secreting glands located in the head.

Snakes feed on a variety of living things, including insects, frogs, mice, snails, and birds. Some snakes eat other snakes. Some eat primarily bird eggs.

What’s for Dinner?

It is easy to see what is on the menu for some snakes—eggs. For others, dinner depends on the species of snake and where it lives. Snakes eat almost any animal that fits into their bodies—fish, frogs, lizards, birds, small mammals—even other snakes.

Like many snakes, egg eaters can eat food that is bigger than their heads. A few egg-eating snakes, such as the African egg eater, have special features for eating eggs. Pointed spines on the neck bones break through the eggshell, allowing the snake to swallow the liquid inside. Then muscles in the snake’s neck crush the shell, which is spit out. Other egg eaters, however, eat the whole egg—shell and all.

Snakes do not need to eat very often. One reason is that they don’t need the food energy to make their own body heat. The other reason is that snakes often eat big meals for their size, so they are not hungry again right away.

Most snakes strike and seize their prey from a coiled position, thrusting the front part of the body forward. Some, however, strike from other positions. Coral snakes, for example, strike by sideswiping the prey with the front of their bodies; a cobra elevates the front of its body and strikes with a forward or downward motion. Some species such as the boas and pythons, although capable of biting, immobilize their prey by coiling and constricting their bodies around the prey, thereby suffocating it.

A snake has a backbone, but no breastbone. Large snakes may have more than 400 vertebrae. Although snakes are limbless, some species show traces of hind limbs in the form of small spurs. Horny scales cover the body; their size, shape, number of rows, and color differ for each species.

Snakes glide or crawl forward with a slithering motion that is aided by muscular contractions of the body and the pushing of the scales against the ground. Snakes known as sidewinders move sideways rather than forward. Contrary to popular belief, snakes do not move swiftly. For example, the coachwhip, considered a fast snake, travels at about 3 mph (4.8 km/h).

In cooler climates, snakes usually mate in the spring, but in the tropics mating occurs at any time. The majority of snakes lay leathery, whitish eggs; the others give birth to live young. In some species, the female incubates the eggs by winding her body around them until they hatch. The number of young varies from 1 to more than 100, depending on the species and individual.

Who Is Hatching from That Egg?

Most species of snakes lay eggs. Depending on the species, a female snake may lay as few as 6 eggs or as many as 100 eggs at one time.

Snake eggs have leathery shells. The shells stretch as the baby snake inside grows. After several weeks, the baby snakes are ready to hatch. A hatching baby snake has a special tooth—an egg tooth—that tears open the shell so that it can wriggle out. Soon after hatching, the baby snake sheds this tooth.

Female snakes lay eggs in holes, burrows, rotten logs, tree stumps, and other such places. A few species of snakes, such as pythons, coil around their eggs to protect them and keep them warm. But most snakes leave their eggs after laying them. The eggs are left to hatch on their own. Some don’t make it. The eggs are eaten by other animals.

The newborn snakes usually shed their skin soon after birth. Thereafter, skins are shed, or sloughed, completely from lip to tail as the snake grows and a larger skin is needed to accommodate the larger body.

Are Snakes in Danger?

More than 50 species of snakes are endangered. Part of the reason is that some people eat snakes. Other people wear snakeskin boots, shoes, and belts. Many snakes are overhunted for these reasons.

Some snakes are in danger because of changes to their habitats. This is true for San Francisco garter snakes. As more land is cleared for farms, homes, businesses, and roads, the snakes have fewer places to live.

Many snake deaths happen by mistake. Common water snakes are often killed by people who mistake them for cottonmouths. Some milk snakes are killed because they look a lot like coral snakes. It is true that poisonous snakes are dangerous. But most snakes are not poisonous.

Kinds of Snakes

Snakes make up the suborder Serpentes of the order Squamata. Some zoologists place snakes in 10 or 13 families, but most zoologists divide them into the following 11 families. The number of species in each family is also in dispute. The numbers given below are generally accepted by most zoologists.

Acrochordidae

This family of Asian river snakes contains two species, the elephant trunk snake, or wart snake, Acrochordus javanicus, and Chersydrus granulatus. Both snakes are hunted for their rough, granular skin, which is used to make shoes and handbags.

Anilidae

The 12 species are commonly called pipe snakes. These snakes are harmless. They have cylindrical bodies and vestiges of hind limbs, and burrow into the ground. Pipe snakes are found in northeastern South America and in southeastern Asia.

Boidae

This family is made up of the boas. It is almost worldwide in distribution, and consists of about 100 species. The snakes are nonvenomous, constricting snakes. Almost all species have vestiges of hind limbs. Many species have sense organs called labial pits in the scales of the lips. The organs are similar in function to the pit vipers' pits.

Colubridae

This family of common, or typical, snakes is made up of about 2,000 species and includes most of the world's snakes. Most are not venomous and those that do produce venom are not deadly. These snakes are found in almost all parts of the world. Members of this family include water snakes, garter snakes, racers, king snakes, milk snakes, bull snakes, and flying snakes.

Elapidae

This family of about 200 species includes the cobras, mambas, and coral snakes. All species are venomous, and the bite of many can be fatal to humans. Members of the family are found in most parts of the world, excluding northern North America and northern Eurasia. Many of these snakes are brightly colored.

Coral snakes are poisonous and marked with bands of black, red, and yellow.Hydrophiidae

Members of this family, called sea snakes, are found in tropical waters. Although found mainly in Southeast Asia, they also inhabit the American Pacific coast from southern Mexico to northern South America. There are about 50 species, ranging from about 2 to 8 feet (60 to 240 cm) in length. They are excellent swimmers and their bodies are slightly compressed from side to side. The tail is greatly compressed from side to side, forming a paddle-like structure used in swimming. These snakes are venomous.

Leptotyphlopidae

Members of this family are also known as blind snakes and resemble the members of the family Typhlopidae. There are about 50 species distributed from the southwestern United States to Brazil and in the West Indies, Africa, and Southeast Asia.

Typhlopidae

There are about 200 species in this family, collectively called blind snakes. These snakes are harmless. They have vestigial (underdeveloped) eyes hidden under scales. Blind snakes are widely scattered throughout the tropics and subtropics.

Uropeltidae

There are about 45 species in this family; they are commonly called shield-tailed snakes. These snakes burrow into the ground. The top of the tail is flattened and shield-shaped, accounting for the snake's common name. They are found in Sri Lanka and southern India.

Viperidae

This family of about 150 species includes the vipers, pit vipers, and rattlesnakes. These snakes have long, curved fangs and are venomous.

Xenopeltidae

The family has one species, the sunbeam snake (Xenopeltis unicolor), found only in Southeast Asia. The sunbeam snake has shiny iridescent scales and grows to a length of 3 feet (90 cm).