A lizard is a reptile closely related to snakes. Like snakes, some lizards are legless. Others resemble snakes but have legs. Many large lizards look much like crocodiles. Lizards vary in size, shape, and color. They have many different ways of moving about and of defending themselves. Scientists have identified almost 3,800 different species of lizards.

In parts of the United States, many people mistake lizards for salamanders. The salamanders are commonly called "spring lizards" or "wood lizards." Salamanders and lizards look much alike, but they are not related. Both are cold-blooded animals. These animals cannot keep their bodies much warmer or cooler than their surroundings. But lizards have dry, scaly skin and clawed toes. Salamanders are amphibians related to frogs, and have moist skin and no scales or claws. Lizards love to stay in the sun, but salamanders usually avoid sunlight.

Where lizards live

Lizards lack the built-in body temperature control many other animals have. So, most lizards live in places where the ground never freezes. Those that live in areas with cold winters must hibernate. Lizards thrive in the tropics and warm parts of the temperate zones. They are the most common reptiles found in deserts and other dry regions. When the desert becomes too hot for comfort, lizards lie in the shade or under the sand to escape the sun's rays.

Sizes of lizards

The smallest lizards are only a few inches or centimeters in length. The largest lizard is the Komodo dragon. This huge East Indian lizard grows about 9 to 10 feet (2.7 to 3 meters) long and may weigh nearly 300 pounds (140 kilograms). The Komodo dragon belongs to a group of lizards known as monitors. Some other monitors grow to be 6 to 7 feet (1.8 to 2.1 meters) in length. These lizards live in Africa, India, and Australia.

How lizards move

The most remarkable thing about lizards is the variety of ways by which they move. More than 65 million years ago, huge lizards called mosasaurs swam in the sea. Even today, giant monitors sometimes swim from one island to another. No present-day lizard can fly, but a small group in Asia and the East Indies glide from tree to tree like flying squirrels. These lizards are the so-called flying dragons. They can spread out a fold of skin along either side of their body by moving several long ribs. This extended fold of skin forms a sort of sail that is used to glide through the air.

Most lizards, however, live on the ground or in trees. Even on the ground, the lizards have many different ways of moving about. Many people in the United States know the swift little lizards that scamper over old fences and logs. Some geckos, lizards that spend much time in trees, have claws that they can draw in as a cat does. Some have slits on their toes that function like suction disks. The claws catch in rough surfaces such as bark, and the slits cling to smoother ones. A gecko can walk upside down across a plaster ceiling without trouble, and can even cling to a pane of glass. The Australian fringed lizard and the basilisk of tropical America can run by raising the front of the body and running on their hind legs.

Many lizards that live on the ground can get along without any legs. Some skinks, for example, have no legs. Other skinks have weak, nearly useless legs. The glass snake of the Eastern United States is really a lizard without legs. It has well-developed eyelids and ear openings, both of which are absent in snakes.

Defenses

Lizards defend themselves in a great variety of ways. Like some snakes, many lizards bluff or play tricks. The glass snake has one of the most unusual methods of defense. This lizard's tail is twice as long as its body, and as brittle as an old twig. If an enemy seizes the lizard's tail, the animal simply breaks off its tail and crawls to safety. Meanwhile, the tail keeps wriggling as though it were alive, fooling the enemy that struggles with it. The lizard does not seem to miss its tail, and in due time it grows a new, shorter one. Several other kinds of lizards, including skinks, can break off their tails and grow new ones to replace them.

Other common ways of bluffing include swelling up, hissing, and lashing the tail. The Australian frilled lizard ranks as one of the best bluffers. This lizard rears on its hind legs, spreads an enormous frill out on each side of its neck, opens its mouth, and hisses. These antics make the frilled lizard look several times as big and fierce as it really is. A large frilled lizard measures about 32 inches (81 centimeters) long.

Some lizards are not such harmless fighters. The monitors and their relatives use their large jaws for biting. They also use their tails as whips to strike a sharp blow. Unlike snakes, few lizards are poisonous. The only poisonous lizards are the Gila monster of the Southwestern United States and northern Mexico, and its close relative, the beaded lizard of Mexico.

The horned lizards have an unusual ability. They can squirt a thin stream of blood from their eyes for a distance of 3 feet (0.9 meter). They use this trick when an enemy attacks them. Sharp spines on their head and back provide added protection. Many people call these lizards horned toads because their body has a flattened, toadlike shape.

The African chameleons are famous for the way they can change color. Many other lizards have the same power. Many persons think that these changes help the animal to protect itself, but they are not always used in this way. Sometimes, these lizards turn a darker color to absorb more heat from the sun's rays. Some lizards do rely on their colors for protection. Many desert lizards are light in hue, and those that dwell in the forest are darker. The different species have various combinations of green, red, gray, brown, white, and black.

Reproduction

Most lizards lay eggs. Some deposit them in simple nests. The female skink may coil around the eggs and drive away any intruders. If the eggs become scattered, she brings them back together.

Some lizards do not lay their eggs but give birth to living young after the eggs hatch in the lizard's body. Others reproduce in somewhat the same way as mammals. These lizards also give birth to living young. Before birth, the developing lizard gets food from the mother's body. Unlike female mammals, the female lizard does not nurse her young or care for them after birth.

Some species of North American whiptails and European lacertid lizards have only female individuals. The adult females lay unfertilized eggs that hatch only into females.

Food

Lizards have less interesting eating habits than snakes. But, unlike snakes, some eat plants instead of animals. The marine iguanas of the Galapagos Islands feed on algae, which they gather off the rocks at low tide. Hundreds of species of lizards eat mostly insects and small animals. Most do not limit their diet to any one thing. A few lizards, such as African chameleons, have a tongue that they can shoot out beyond their snout. They capture insects on their tongue's mucus-coated tip. Other lizards seize their victims in their mouths. They swallow their prey as soon as it stops struggling.

Dangers to lizards

Human activities threaten the survival of certain species of lizards. People gather lizard eggs and hunt iguanas and other lizards for food in some countries. In many areas, the animal's habitats have been destroyed. In the past, some lizards were killed for their skins, which were used to make wallets, handbags, and other products. But many countries now forbid killing lizards for this purpose.

Scientific classification

Lizards belong to the class Reptilia. They are members of the order Squamata, along with snakes. Lizards alone make up the suborder Lacertilia (sometimes called Sauria).