Lizards: A Comprehensive Guide to These Scaly Reptiles

Lizard Browse the article Lizard

Introduction to Lizard

Lizard, a scaly reptile closely related to snakes. Lizards live chiefly in warm regions. Many inhabit deserts and semiarid regions; others live in fields and forests. Most dwell on the ground; some burrow into the soil; still others spend much of their time either in trees or in water.

The banded gecko is a lizard native to the southwestern United States.

Description

In length, lizards range from the half inch (1.5 cm) of the smallest gecko to the more than 10 feet (3 m) of the dragon of Komodo. In weight, they range from 5 ounces (140 g) to more than 250 pounds (113 kg). A number of lizards are shaped like toads with short tails, and others like snakes and worms. Most have well-defined heads and necks, elongated bodies, and tapering tails. Most lizards have four limbs, each ending in five clawed toes. Some have only vestiges (traces) of limbs in their skeletons.

A typical lizard has a small, disc-shaped organ called the pineal body on top of its head. Nerve tissue extends from this organ to the brain. Research suggests that the pineal body helps regulate the lizard's biological clock.

Tail

In many species, the lizard's tail will easily break off from the body, allowing the animal to escape if seized by the tail. The lizard will grow a new tail, which will usually be shorter than the old and will contain a gristly rod or tube instead of bone. A new tail will grow also from a break in the tail. That is why some lizards have two or three tails.

Skin

A lizard has scaly skin. The scales are sometimes grainy, spiny, or beadlike. From time to time the lizard sheds its outer skin. Some lizards are brightly colored, but most are colored in dull shades that match their backgrounds. Chameleons and some others can change color to a limited extent.

Eyes, Ears, and Tongue

Almost all lizards have two ear holes and two eyes with movable lids. In those lacking eyelids, the eye is protected by a transparent membrane. Lizards have fairly good hearing and sight, and they can see colors. The chameleon can move each eye independently.

The tongue of an insect-eating lizard is long and covered at the end with sticky saliva. It can be swiftly thrust out to catch insects. A number of lizards have forked tongues that aid in smelling. The tongue is flicked out and in to carry odor-bearing particles to the smelling organs on the roof of the mouth.

Habits

Most lizards eat insects, spiders, and scorpions. Iguanas and some others live chiefly on plant food. Monitors and a number of other lizards eat amphibians, reptiles, birds, and mammals. The dragon of Komodo catches and eats animals as large as deer.

Iguanas are chiefly plant eating lizards.

Lizards are preyed upon by snakes, birds, and various other meat-eating animals. Some, such as iguanas, are eaten by human beings. Some are killed for their skins, which are made into shoes, handbags, and other items. Some lizards, such as the tegu and the chameleon, are kept as pets.

Most lizards reproduce sexually—that is, their eggs must be fertilized to produce offspring. Some lizards, such as whiptails, sometimes reproduce asexually—their eggs produce offspring without being fertilized. Lizards of most species are hatched from eggs laid beneath a log or buried in soil. The young of some species hatch from eggs with in the mother's body or are born fully developed. Lizards generally must fend for themselves from birth.

What Are the Dangers for Lizards’ Eggs in a Nest?

Most lizard eggs are not waterproof. The shells have to be able to let moisture in so that the growing lizards can get the moisture they need to develop and hatch properly. The female lizards often lay their eggs in damp soil, fallen leaves, and rotting wood, all of which have the necessary moisture. Even sand can be a safe place for a nest, if the lizard digs down far enough to reach some water.

After laying their eggs, most females leave them alone to develop and hatch. The eggs are easy targets for other animals—they make the perfect snack. In most species of lizard, the eggs are white and are easy for animals to spot in a nest that is not well hidden. In some Central and South American countries, people eat lizard eggs.

Most female lizards lay eggs. But the females of some species give birth to live young. Among lizards that do lay eggs, most eggs require several weeks or even a few months to hatch. The eggs of a panther chameleon may need 240 or more days to develop before hatching.

Lizards are unable to maintain a constant body temperature. For this reason they must shelter in cool places in hot weather, and hibernate in burrows or other protected places in winter.

Lizards can run at a rate of up to 15 miles an hour (24 km/h), and many kinds depend on speed to escape enemies. Many lizards are protectively colored. Horns and spines protect the horned toad and many other lizards. Almost all lizards can, and will, bite, but only the Gila monster and the Mexican beaded lizard are venomous. To frighten or confuse enemies, the horned toad squirts blood from its eyes, while the frilled lizard spreads the large disk of skin about its neck in order to appear larger to its enemies.

What’s All That Head-bobbing About?

Head-bobbing is a way that lizards communicate. Male anoles nod their heads up and down to signal to other anoles that they are males and to chase off other males at mating time.

Bobbing sometimes means a male is ready to fight another animal. It also can mean that the animal is defending its territory.

Some lizards do “push-ups” for the same reason. They push up with their front legs, which may make them look larger to an opponent.

Each species of lizard has its own pattern of head-bobbing and push-ups. This is one way in which lizards can tell which individuals belong to their own species.

Other ways in which lizards communicate include waving their tails, opening their jaws wide, changing their colors, sticking out their dewlaps, or showing off their brightly colored undersides.

Do Lizards Have Many Ways to Defend Themselves?

Yes, lizards defend themselves in many ways.

The most common self-defense for a lizard is running away. But some lizards do the opposite: they freeze when they see an enemy, counting on their camouflage colors or bright patterns to help hide them. A few species of lizards even “play dead.” These lizards hope they will not be interesting to a predator if that predator thinks they are already dead.

Just as the glass lizard uses its tail to distract an attacker, other lizards also bluff, or play tricks. Some try to look more fierce than they are by lashing their tails, hissing, or puffing out their bodies to look larger.Some lizards, including monitors, use their jaws for biting. They clamp their jaws and sink their teeth into an attacker’s body and then hang on. Even a lizard that is not poisonous can do a lot of damage by biting its enemy.

Are Lizards in Danger?

Some species of lizard are endangered, and others are threatened. In many areas, the lizards’ habitats have been destroyed. Forests have been cut down, roads have been built, and wetlands have been drained or dammed.

In the past, some lizards were killed for their skins. These skins were used to make wallets, handbags, and other products. But many countries now forbid killing lizards for this purpose. In some countries, people still kill lizards to eat, or eat the lizards’ eggs.

Marine iguanas are threatened by oil spills near their home in the Galapagos Islands. There was a bad oil spill near the Galapagos Islands in 2001. The next year, scientists said that about 15,000 marine iguanas had died on a nearby island.

More than two dozen species of lizards are officially called endangered, and many more are considered vulnerable. Among the endangered species are the Fiji crested iguana, the Coachella Valley fringe-toed lizard, and a legless species of skink.

Kinds of Lizards

Lizards belong to the suborder Sauria of the order Squamata. There are 16 families and more than 3,700 species of lizards. About 30 species are native to the United States, chiefly to the West.

Agamid Lizards

of the Eastern Hemisphere include the frilled lizard and the thorny dragon of Australia and the ftying dragon of southeastern Asia.

Agamid lizards belong to the family Agamidae. The frilled lizard is Chlamydosaurus kingii; flying dragon, Draco volans; thorny dragon, Moloch horridus.

Anguid Lizards

have streamlined bodies. Some have no limbs; others have short limbs. Anguid lizards include the glass snakes of the southern United States, the alligator lizards of the western United States, the slowworm of the Eastern Hemisphere, and the California legless lizard.

Anguid lizards belong to the family Anguidae. Glass snakes belong to the genus Ophisaurus; alligator lizards to the genera Elgaria and Gerrhonotus. The slowworm is Anguis fragilis; the California legless lizard is Anniela pulchra.

Which Lizard Is Often Mistaken for a Snake?

Glass lizards are often mistaken for snakes. These lizards have no legs, and they are long and slender in shape. They are called glass lizards because their tails are very brittle and can easily snap off.

Many people call these lizards glass snakes. But glass lizards have ear openings and movable eyelids. Snakes do not.

Glass lizards live in the southeastern and central parts of the United States and in Mexico, Europe, Asia, and Africa. Some of these lizards grow to be about 2 feet (0.6 meter) long, with tails that are twice as long as their bodies. There are 14 species, or types, of glass lizard.

What Trick Can Glass Lizards Do With Their Tail?

A glass lizard’s tail is very fragile, or easily broken. A predator can snap off the glass lizard’s tail during an attack. But this can actually be a good thing. The tail can wriggle for a short time after breaking off. This may distract the attacker and allow the glass lizard to escape. The lizard does not seem to miss its tail. In time it grows a new, shorter tail.

Several other kinds of lizard, including geckos and skinks, can break off their tail and grow a new one. The same lizard can lose its tail many times and grow a new one after each loss. The new tail may be shorter and fatter, and may have different markings. It begins to grow right after the old tail is snapped off.

Lizards’ tails are used for many other things in addition to defense. They help the lizards balance while walking or running. They store fat, which can be used when food is scarce. And, some lizards also use their tails as an “extra leg” to grasp branches while they climb.

Beaded Lizards

include the Gila monster and its close relative, the Mexican beaded lizard, or horrid heloderm, of Mexico and Central America.

Chameleons

are tree-dwelling lizards that can change color.

Chameleons belong to the family Chamaeleontidae.

Geckos

are chiefly tree-dwellers that are active at night.

Geckos belong to the family Gekkonidae.

Iguanas

are large lizards, up to six feet (1.8 m) long, that live chiefly in tropical America. Several species occur in the United States, including the desert iguana of western deserts, and the collared lizards, basilisks, swifts, spiny lizards, fence lizards, horned toads, and chuckwallas that live chiefly in the West and Southwest. The anoles of the Southeast also belong to this family.

Iguanas belong to the family Iguanidae. The desert iguana is Dipsosaurus dorsalis. Collared lizards belong to the genus Crotaphytus; basilisks, Basiliscus; swifts and spiny and fence lizards, Sceloporus; horned toads, Phrynosoma; chuckwallas, Sauromalus; anoles, Anolis.

Monitors

are large Old World lizards. Many live near rivers. Monitors eat fish, birds, and any other animals they can overpower. This group includes the Nile monitor, which grows to be six feet (1.8 m) long, the goanna of Australia, and the dragon of Komodo.

Monitors belong to the family Varanidae. The Nile monitor is Varanus niloticus; goanna, V. varius; dragon of Komodo, V. komodoensis.

Night Lizards

are found in western deserts. They have large, protruding eyes with vertical pupils but without movable eyelids.

Night lizards belong to the family Xantusidae.

Skinks

most common of all lizards, are found in almost all parts of the world.

Skinks belong to the family Scincidae. The stumplailed skink is Trachysaurus rugosus.

Wall and Sand Lizards

are widespread in Europe, Africa, and Asia. They have conical heads and well-developed limbs. Wall lizards, such as the viviparous lizard, are usually seen among rocks or on walls. Sand lizards, such as the European sand lizard, are usually seen in sandy, open areas.

Wall and sand lizards belong to the family Lacertidae. The viviparous lizard is Lacerta vivipara; the European sand lizard, L. agilis.

Whiptails and Racerunners

are native to the Americas. Their tails are often twice as long as their bodies. They are noted for speed. In the United States they do not exceed 12 inches (30 cm) in length, but they grow to 48 inches (120 cm) in the tropics. The tegu usually grows to be 36 inches (90 cm) long.

Whiptails and racerunners belong to the family Teiidae. The tegu is Tupinambis teguixin.

Which Species of Lizard Have Only Female Offspring?

Most animals, including lizards, need both a female and a male to mate in order to reproduce, or have offspring. But the females of about 30 species of lizard can reproduce when a male is not present.

The offspring of these lizards are all female. A single female lizard is able to lay eggs or give birth to young lizards that are clones of (genetically identical to) their mother. The females of 10 species of whiptail lizard from the southwestern United States and Mexico are among those who reproduce without males.

There are pluses and minuses to being able to reproduce without a male. One good thing is that the lizards do not need to spend time finding or fighting over mates. Because of this, a group can increase in size quickly. But one bad thing is that the offspring are genetically identical to their mother (and to each other). Genetic diversity is good for a species. It gives a species a better chance of adapting to different or changing environments.

Worm Lizards

are burrowing lizards shaped like worms. They have no ear holes, and their eyes are partly covered with skin. The Florida worm lizard, pink to red, grows to a length of 14 inches (35 cm). Worm lizards are also found in South America, Spain, and Africa.

Worm lizards belong to the family Amphisbaenidae. The Florida worm lizard is Rhineurafloridana.